Category: learner thinking

Making molecular mechanisms familiar

A reflection on the pedagogy in Andrew Scott's 'Vital Principles'

Keith S. Taber

Andrew Scott's introduction to the chemistry of the cell is populated by a diverse cast of characters, including ballot machines, beads; blind engineers and blind-folded art-seekers; builders and breaker's yards; cars, freight vehicles and boats; Christmas shoppers, dancers; gatecrashers (despite gatekeepers) and their hosts; invaders, jack-in-the-boxes, legal summonses, light bulbs, mixing bowls, maelstroms, music tapes, office blocks; oceans, seas, rivers, streams, floods and pools; skeletons and their bones, split personalities, springs; sorting offices and postal systems; turnstiles, the water cycle, water wheels, ropes, pulleys and pumps; work benches and work stations; and weeding and seaweed forests.

Scott, A. (1988). Vital Principles. The molecular mechanisms of life. Basil Blackwell.

The task of the popular science writer

This piece is not a formal review of, what is, now, hardly a recent title 1, but a reflection on an example of a science book aimed at – not a specific level of student, but – a more general audience. The author of a 'popular science book' has both a key advantage over the author of many science textbooks, and a challenge. The advantage is being able to define your own topic – deciding what you wish to cover and in how much detail. By contrast, a textbook author, certainly at a level related to formal national examination courses, has to 'cover' the specified material. 2

However the textbook author has the advantage of being able to rely on a fairly well defined model of the expected background of the readership. 3 Students taking 'A level' physics (for example) will be expected to have already covered a certain range of material at a known level through science teaching at school ('G.C.S.E. level') and to have also demonstrated a high level of competence against the school maths curriculum. This is important because human learning is incremental, and interpretive, and so iterative: we can only take in a certain amount of new material at any time, and we make sense of it in terms of our pool of existing interpretative resources (past learning and experiences, etc.) 4

The teacher or textbook author designs their presentation of material based on a mental model of the interpretive resources (e.g., prerequisite learning, familiar cultural referents that may be useful in making analogies or similes, etc.) available to, and likely to be activated in the mind of, the learner when engaging with the presentation.

So, the science teacher works with a model of the thinking of the students, so as to pitch material in manageable learning quanta, that should relate to the prior learning. The teacher's mental model can never be perfect, and consequently teaching-learning often fails (so the good teacher becomes a 'learning doctor' diagnosing where things have gone wrong). However, at least the teacher has a solid starting point, when teaching 11 year olds, or 15 year olds, or new undergraduates, or whatever.

The textbook author shares this, but the popular science author has a potential readership of all ages and nationalities and levels of background in the subject. Presumably the reader has some level of interest in the topic (always helpful to support engagement) but beyond that…

Now the role of the science communicator – be they research scientist with a general audience, teacher, lecturer, textbook author, journalist, documentary producer, or popular science author – is to make what is currently unfamiliar to the learner into something familiar. The teacher needs to make sure the learners both have the prerequisite background for new teaching and appreciate how the new material relates to and builds upon it. Even then, they will often rely on other techniques to make the unfamiliar familiar – such as offfering analogies and similes, anthropomorphism, narratives, models, and so forth.

Read about making the unfamiliar familiar

As the popular science writer does not know about the background knowledge and understanding of her readers, and, indeed, this is likely to be extremely varied across the readership, she has to reply more on these pedagogic tactics. Or rather, a subset of these ways of making the unfamiliar familiar (as the teacher can use gestures, and computer animations, and physical models; and even get the class to role-play, say, electrons moving through a circuit, or proteins binding to enzymes). Thus, popular science books abound with analogies, similes, metaphors and the like – offering links between abstract scientific concepts, and what (the author anticipates) are phenomena or ideas familiar to readers from everyday life. In this regard, Andrew Scott does not disappoint.

Andrew Scott

Scott's website tells us he has a B.Sc. in biochemistry from Edinburgh, and a Ph.D. from Cambridge in chemistry, and that he has produced "science journalism published by academic publishers, newspapers, magazines and websites", and he is an "author of books translated into many languages". I have not read his other books (yet), but thought that Vital Principles did a good job of covering a great deal of complex material – basically biochemistry. It was fairly introductory (so I doubt much could be considered outdated) but nonetheless tackled a challenging and complex topic for someone coming to the book with limited background.

I had a few quibbles with some specific points made – mainly relating to the treatment of underpinning physics and chemistry 5 – but generally enjoyed the text and thinking about the various comparisons the author made in order to help make the unfamiliar familiar to his readership.

Metaphors for molecular mechanisms

Andrew Scott's introduction to the chemistry of the cell is populated by a diverse cast of characters, including ballot machines, beads; blind engineers and blind-folded art-seekers; builders and breaker's yards; cars, freight vehicles and boats; Christmas shoppers, dancers; gatecrashers (despite gatekeepers) and their hosts; invaders, jack-in-the-boxes, legal summonses, light bulbs, mixing bowls, maelstroms, music tapes, office blocks; oceans, seas, rivers, streams, floods and pools; skeletons and their bones, split personalities, springs; sorting offices and postal systems; turnstiles, the water cycle, water wheels, ropes, pulleys and pumps; work benches and work stations; and weeding and seaweed forests.

A wide range of metaphors are found in the book. Some are so ubiquitous in popular science discourse that it may be objected they are not really metaphors at all. So, do "… 'chloroplasts'…trap the energy of sunlight…"? This is a simplification of course (and Scott does go into some detail of the process), but does photosynthesis actually 'trap' the energy of sunlight? That is, is this just a simplification, or is it a figurative use of language? Scott is well aware that energy is not a concept it is easy to fully appreciate,

"Energy is really an idea invented by mankind, rather than some definite thing…

energy can be thought of as some sort of 'force resistance' or 'antiforce' able to counteract the pushes or pulls of the fundamental forces."

pp.25-26

But considerable ingenuity has been used in making the biochemistry of the cell familiar through metaphor:

  • lipids "have split personalities" (and they have 'heads' and 'tails' of course)
  • proteins can "float around within a sea of lipid"
  • proteins are "the molecular workers"
  • the inside of cells can be a "seething 'metabolite pool' – a maelstrom of molecules"; "a swirling sea of chemical activity…the seething sea of metabolism" (so, some appealing alliteration, as well, here 6);
  • the molecules of the cell cytosol are "dancing"
  • "...small compressed springs of ATP, can be used to jack up the chemistry of the cell…"
  • "…thermal motion turns much of the chemical microworld into a molecular mixing bowl."
  • "The membranes of living cells…form a boundary to all cells, and they cordon off specific regions within a cell into distinct organelles."
  • "Some of these gatecrashers within other cells would then have slowly evolved into the mitochondria and chloroplasts of present-day life..."
  • "the 'Ca2+ channels' to open up, this causes Ca2+ ions to flood into the cell …"
  • "the 'ribosomes' … are the chemical automatons…"

The figurative flavour of the author's language is established early in the book,

"In a feat of stunning self-regulating choreography, billions of atoms, molecules and ions become a part of the frantic dance we call life. Each revolution of our planet in its stellar spotlight raises a little bit of the dust of earth into the dance of life, while a little bit of the life crumbles back into dust."

p.1

Phew – there is quite a lot going on there. Life is a dance, moreover a frantic dance, of molecular level particles: but not some random dance (though it relies on molecular motion that is said to be a random dance, p.42), rather one that is choreographed, indeed, self-choreographed. Life has agency. It is a dance that is in some sense powered by the revolution of the earth (abound its axis? around its star?) which somehow involves the cycling of dust into, and back out, of life – dust to dust. The reference to a stellar spotlight seems at odds with the Sun as symmetrically radiating in all directions out into the cosmos – the earth moves through that radiation field, but could not escape it by changing orbit. Perhaps this image is meant to refer to how the daily rotation of the earth brings its surface into, and out of, illumination.

So, there is not a spotlight in any literal, sense (the reference to "the central high energy furnace", p.39, is perhaps a more accurate metaphor), but the 'stellar spotlight' is a metaphor that offers a sense of changing illumination.

Similarly, the choreographed dance is metaphorical. Obviously molecules do not dance (a deliberate form of expression), but this gives an impression of the molecular movement within living things. That movement is not choreographed in the sense of something designed by a creator. But something has led to the apparently chaotic movements of billions of molecules and ions, of different kinds, giving rise to highly organised complex entities (organisms) emerging from all this activity. Perhaps we should think of one of those overblown, heavily populated, dance sequences in Hollywood films of the mid 20th century (e.g., as lampooned in Mel Brook's Oscar winning 'The Directors')?

So, in Vital Principles, Scott seeks to make the abstract and complex ideas of science seem familiar through metaphors that can offer a feel for the basic ideas of biochemistry. The use of metaphor in science teaching and other forms of science communication is a well established technique.

Read about science metaphors

Nature and nurture

Later in the book a reader will find that the metaphorical choreographer is natural selection, and natural selection is just the tautological selection of what can best reproduce itself in the environment in which it exists,

"…the brute and blind force of natural selection can be relied upon to weed out the harmful mutations and nurture the beneficial ones. We must always remember, however, that the criterion by which natural selection judges mutations as harmful or beneficial is simply the effect of the mutations on an organism's ability to pass its genetic information on to future generations."

p.182

So, natural selection is a force which is brute and blind (more metaphors) and is able to either weed out (yes, another metaphor) or nurture. That is an interesting choice of term given the popular (but misleadingly over-simplistic) contrast often made in everyday discourse between 'nature' (in the sense of genetics) and 'nurture' (in the sense of environmental conditions). Although natural selection is 'blind', it is said to be able to make judgements.

Form and function in biology

Here we enter one of the major issues in teaching about biology: at one level, that of a naturalistic explanation 7, there is no purpose in life: and anatomical structures, biochemical processes, even instinctive behaviours, have no purpose – they just are; and because they were components of complexes of features that were replicated, they have survived (and have 'survival value').

Yet, it seems so obvious that legs are for walking, eyes are for seeing, and the heart's function is to pump blood around the body. A purist would deny each of these (strictly these suggestions are teleological) and replace each simple statement with a formally worded paragraph completely excluding any reference to, or hint at, purpose.

So, although it seems quite natural to write

"…hormones… are released from one cell to influence the activity of other cells;

…neurotransmitters…are released from nerve cells to transmit a nerve impulse…"

pp.120-121

we might ask: is this misleading?

One could argue that in this area of science we are working with a model which is founded on the theory of natural selection and which posits the evolved features of anatomy, physiology, biochemistry,etc., that increase fitness are analogous to designed and purposeful features that support the project of the continuation of life.

Something that scientists are very quick to deny (that organisms have been designed with purposes in mind) is nevertheless the basis of a useful analogy (i.e., we can consider the organism as if a kind of designed system that has coordinated component parts that each have roles in maintaining the 'living' status of the overall system). We then get the economy of language where

  • hormones and neurotransmitters are released for 'this' purpose, to carry out 'that' function;

being selected (!) over

  • more abstract and complex descriptions of how certain patterns of activity are retained because they are indirectly selected for along with the wider system they are embedded in.

Do scientists sometimes forget they are working with a model or analogy here? I expect so. Do learners appreciate that the 'functions' of organs and molecules in the living thing are only figurative in this sense? Perhaps, sometimes, but – surely -more often, not; and this probably both contributes to, and is encouraged by, the known learning demand of appreciating the "blind [nature of the] force of natural selection".

Scott refers to proteins having a particular task (language which suggests purpose and perhaps design) whilst being clear he is only referring to the outcomes of physical interactions,

"A protein folds up into a conformation which is determined by its amino acid sequence, and which presents to the environment around it a chemical surface which allows the protein to perform its particular chemical task; and the folding and the performance of the task (and, indeed, the creation of the protein in the first place) all proceed automatically governed only by physical laws and forces of nature – particularly the electromagnetic force."

pp.54-55

In practice, biologists and medical scientists – and indeed the rest of us – find it much more convenient to understand organisms in terms of form and function. That is fine if you always keep in mind that natural selection only judges mutations metaphorically. Natural selection is not the kind of entity which can make a judgement, but it is a process that we can conceptualise as if it makes judgements.

This is a difficult balancing act:

"Nature is a blind but a supremely effective engineer. Through the agency of undirected mutation she continually adjusts the structure and the mechanisms of the living things on earth."

p.182

Nature is here treated as if a person: she is an engineer tinkering with her mechanisms. Personification of nature is a long-standing trope, once common among philosophers and not always eschewed by scientists in their writings (e.g., Nicolaus Copernicus, Henri Poincaré, Michael Faraday, even Albert Einstein have personified Nature) – and she is always female.

But usually a competent engineer tinkers according to a plan, or at least with a purpose in mind, whereas nature's tinkering is here described as 'undirected' – it is like she arbitrarily changes the size of a gear or modifies the steam pressure in a cylinder or changes the number of wheels on the locomotive, and then tinkers some more with those that stay on the tracks and manage to keep moving.

Read about personification in science

"All proteins begin life…"

Anthropomorphism: living metaphors

Personification (by referring to her, she, etc.) is not needed to imply entities have some human traits. Indeed, a very common pedagogic technique used when explaining science, anthropomorphism, is to use a kind of metaphorical language which treats inanimate objects or non-human beings as if they are people – as if they can feel, and think, and plan, and desire; and so forth.

  • "Once an enzyme had met and captured the required starting materials …"
  • "Some [non-protein metabolites] act as 'coenzymes', which becomes bound to enzymes and help them to perform their catalytic tasks."
  • "Cells, which had previously been aggressively independent individualists, discovered the advantages of communal life."
  • "…descendants of cells which took up residence within other cells and then became so dependent on their hosts, and also so useful to them, that neither hosts nor gatecrashers could afford to live apart."

So, for example, plants are living beings, but do not have a central nervous system and do not experience and reflect on life as people do: so, they do not wish for things,

"…the oxidation of sugars, is also performed by plants when they wish to convert some of their energy stores (largely held in the form of complex carbohydrates) back into ATP."

p.144

Again, such phrasing offers economy of language. Plants do not wish, but any technically correct statement would likely be more complicated and so, arguably, more difficult to appreciate.

Dead metaphors

A key issue in discussing metaphors is that in many cases different readers are likely to disagree over whether a term is indeed being used figuratively or literally. Language is fluid (metaphorically speaking), and a major way language grows is where the need for new terms (to denote newly invented artefacts or newly discovered phenomena) is satisfied by offering an existing term as a metaphor. Often, in time the metaphor becomes adopted as standard usage – so, no longer a metaphor. These examples are sometimes called dead metaphors (or clichéd metaphors). So, for example, at some point, many decades ago, astronomers started to talk of the 'life cycle' of stars which have a moment of 'birth' and eventual 'death'. These metaphors have become so established they are now treated as formal terms in the language of the discipline, regularly used in academic papers as well as more general discourse (see 'The passing of stars: Birth, death, and afterlife in the universe').

So, when Scott writes of "how some micro-organism, say a virus, invades the body…"(p.109) it is very likely most readers will not notice 'invade' as being a metaphor, as this usage is widely used and so probably familiar. The (former?) metaphor is extended to describe selective immune components "binding to foreign invaders [that] can act as a very effective means of defence against disease." These terms are very widely used in discussing infections: though of course there are substantive differences, as well as similarities, with when a country defends itself against actual foreign invaders.

I suspect that considering the lipid bilayer to be "a stable sandwich of two layers of lipid molecules" (p.115) is for many, a dead metaphor. The reference to a DNA double-helix leading to"two daughter double-helices" reflects how atomic nuclei and cells are said to give rise to 'daughters' on fission: again terminology that has become standard in the field.

Sharing a psuedo-explanation for covalent bonding

One phrase that seems to have become a dead metaphor is the notion of electrons being 'shared' in molecules, which "…are formed when their constituent atoms come together to leave at least some of their electrons shared between them" (pp.28-29). Whilst this seems harmless as a description of the structure, it is also used as an explanation of the bonding:

"'hydrogen molecules and water molecules (and all other molecules) are held together by virtue of the fact that electrons are shared between the individual atoms involved, a similarity recognised by saying that in such cases the atoms are held together by 'covalent' bonds.

p.29

But we might ask: How does 'sharing' a pair of electrons explain the molecule being 'held together'? Perhaps a couple with a strained relationship might be held together by sharing a house; or two schools in a confederation by sharing a playing field; or two scuba divers might be held together if the breathing equipment of one had failed so that they only had one functioning oxygen cylinder shared between them?

In these examples, there is of course a sense of ownership involved. Atoms do not 'own' 'their' electrons: the only bonds are electromagnetic; not legal or moral. This may seem so obvious it does not deserve noting: but some learners do come to think that the electrons are owned by specific atoms, and therefore can be given, borrowed, stolen, and so forth, but should ultimately return to their 'own' atom! So, if we acknowledge that there is no ownership of electrons, then what does it even mean for atoms to 'share' them?

So, why would two atoms, each with an electron, become bound by pooling these resources? (Would sharing two houses keep our couple with a strained relationship together; or just offer them a ready way to separate?) The metaphor does not seem to help us understand, but the notion of a covalent bond as a shared electron pair is so well-established that the description commonly slips into an explanation without the explainer noticing it is only a pseudo-explanation (a statement that has the form of an explanation but does not explain anything, e.g., "a covalent bond holds two atoms together because they share a paired of electrons").

Read about types of pseudo-explanation

Elsewhere in the book Scott does explain (if still anthropomorphically) that viable reactions occur because:

"In the new configuration, in other words, the electromagnetic forces of attraction and repulsion between all the electrons and nuclei involved might be more fully satisfied, or less 'strained' than they were before the reaction took place."

p.36

How are metaphors interpreted?

The question that always comes to my mind when I see metaphorical language used in science communication, is how is this understood by the audience? Where I am reading about science that I basically understand reasonably well (and I was a science teacher for many years, so I suspect I cannot be seen a typical reader of such a book) I do reflect on the metaphors and what they are meant to convey. But that means I am often using the familiar science to think about the metaphor, whereas the purpose of the metaphor is to help someone who does not already know the science get a take on it. This leads me to two questions:

  • to what extent does the metaphor give the reader a sense of understanding the science?
  • to what extent does the metaphor support the reader in acquiring an understanding that matches the scientific account?

These are genuine questions about the (subjective and objective) effectiveness of such devices for making the science familiar. There is an interesting potential research programme there.

Shifting to similes

The difference between metaphors and similes is how they are phrased. Both make a comparison between what is being explained/discussed and something assumed to be more familiar. A metaphor describes the target notion as being the comparison (nature is an engineer), but the listener/reader is expected to realise this is meant figuratively, as a comparison. A simile makes the comparison explicit. The comparison is marked – often by the use of 'as' or 'like' as when physicist Max Planck suggested that the law of conservation of energy was "like a sacred commandment".

Read about examples of similes in science

So, when Scott refers to how proteins "act as freight vehicles transporting various chemicals around the body", and "as chemical messages which are sent from one cell to another" (p.10), these are similes.

Springs are used as similes for the interactions between molecules or ions in solids or the bonds within molecules

"…even in solids the constituent molecules and atoms and ions are constantly jostling against one another and often vibrating internally like tiny sub-microscopic springs. All chemical bonds behave a bit like tiny springs, constantly being stretched and compressed as the chemicals they are part of are jostled about by the motion of the other chemicals all around them."

p.39

[Actually the bonds in molecules or crystals are behaving like springs because of the inherent energy of the molecule or lattice: the 'jostling' can transfer energy between molecules/ions and 'springs' so that the patterns of "being stretched and compressed" change, but it is always there. The average amount of 'jostling' depends on the temperature of the material. 5]

In the way the word is usually used in English, jostling is actually due to the deliberate actions of agents – pushing through a crowd for example, so strictly jostling here can be seen as an anthropomorphic metaphor, but the intended meanings seems very clear – so, I suspect many readers will not even have noticed this was another use of figurative language.


One way of marking phrases meant as similes is putting then in inverted commas, so-called scare-quotes, as in

"A rather simple chemical 'cap', for example, is added to the start of the RNA, while a long 'tail' consisting of many copies of the nucleotide A is added to its end…The most significant modifications to the precursor, however, involve the removal of specific portions from the interior [sic] of the RNA molecule, and the joining together of the remaining portions into mature mRNA… This 'splicing' process …"

p.79

Here we have something akin to a cap, and something akin to a tail. As noted above, a difficulty in labelling terms as metaphors or similes is that language is not static, but constantly changing. In science we often see terms borrowed metaphorically from everyday life to label a technical process as being somewhat like something familiar – only for the term to become adopted within the field as a technical term. The adopted terms become literal, with a related, but somewhat different – and usually more precise – meaning in scientific discourse. (This can be the basis of one class of learning impediments as students may not realise the familiar term has specials affordances or restrictions in its technical context.)

Here 'splicing' is marked as a simile – there is a process seen as somewhat similar to how, for example, radio programmes and musical recordings used to be edited by the cutting and resequencing strips of magnetic tape. Yet gene splicing is now widely accepted as a literal use of splicing, rather than being considered figurative. [I suspect a young person who was told about, for example, the Beatles experiments with tape splicing might guess the term is used because the process is like gene splicing!]

The following quote marks a number of similes by placing them within inverted commas:

"The interior of the cell is criss-crossed by a network of structural proteins which is known as the cytoskeleton. The long protein 'bones' of this skeleton are formed by the spontaneous aggregation of many individual globular protein molecules…

Cells use many strong chemical 'pillars' and 'beams' and 'glues' and 'cements', both inside them, to hold the internal structure of cells together, and outside of them, to hold different cells together; but the electromagnetic force is the fundamental 'glue' upon which they all depend."

pp.995-6

Again the phrasing here suggests something being deliberately undertaken towards some end by an active agent (teleology): the cell uses these construction materials for a purpose.

There are various other similes offered – some marked with inverted commas, some with explicit references to being comparisons ('kind of', 'act as', 'sort of', etc.)

  • "…amino acids comprise the chemical 'alphabet' from which the story of protein-based life (i.e., all life on earth) is constructed"
  • "the endoplasmic reticulum is a kind of molecular 'sorting office'…"
    • endosomes and lysomes "form a kind of intracellular digestive system and 'breaker's yard'."
    • "Proteins can act as gatekeepers of the cell…"
    • "Proteins can…act as chemical controllers"
    • proteins "can act as defensive weapons…"
    • "The proteins which perform these feats are not gates, but 'pumps'..."
    • "Proteins could be described as the molecular workers which actually construct and maintain all cells…"
    • "…proteins are the molecular 'labourers' of life, while genes are the molecular 'manuals' which store the information needed to make new generations of protein labourers…"
    • "Membrane proteins often float around within a sea of lipid (although they can also be 'held at anchor' in the one spot if required)"
    • "A ribosome travels down its attached mRNA, a bit like a bead running down a thread (or sometimes like a thread being pulled through a bead)..."
    • "…the 'ribosomes' – molecular 'work-benches' composed of protein and RNA…"
    • Nucleic acids "act as genetic moulds"
    • "the high energy structure of ATP really is very similar to the high energy state of a compressed spring"
    • "Some vital non-protein metabolites act as a sort of 'energy currency'…"

Advancing to analogies

Metaphors and similes point out a comparison, without detailing the nature and limits of that comparison. A key feature of an analogy is there is a 'structural mapping': that is that two systems can be represented as having analogous structural features. In practice, the use of analogy goes beyond suggesting there is a comparison, to specifying, at least to some degree, how the analogy maps onto the target.

Read about examples of analogies in science

Scott employs a number of analogies for readers. He develops the static image of the cell skeleton (met above) with its 'bones', 'pillars' and 'beams' into a dynamic scenario:

"Structural proteins are often referred to as the molecular scaffolding of life, and the analogy is quite apt since so many structural proteins are long fibres or rods; but we think of scaffolding as a static, unchanging, framework. Imagine, however, a structure built of scaffolding in which some of the scaffolding rods were able to slide past one another and then hold the whole framework in new positions."

p.96

Many good metaphors/similes may be based upon comparisons of this type, but they do not become analogies until this is set out, rather than being left to the listener/reader to deduce. For this reason, analogies are better tools to use in teaching than similes as they do not rely on the learners inferring (guessing?) what the points of comparison are intended to be. 8

So, Scott offers the simile of molecules released as 'messengers', but then locates this in the analogy of the postal system, before using another analogy to specify the kind of message being communicated,

"Cells achieve such chemical communication in various ways, but the most vital way is by releasing chemical 'messenger' molecules (the biological equivalent of the postal system, if you like analogies), and many of these messengers are either proteins, or small fragments of proteins."
…
"A biological messenger molecular is more like a legal summons than a friendly note or some junk mail advertisement – it commands the target cell to react in a precise way to the arrival of the message."

pp.102-103

In the following analogy the mapping is very clear:

"One gene occupies one region of a chromosome containing many genes, much like one song occupies one region of a music tape containing many songs overall."

p.7

Song on music tape is to gene on chromosome

For an analogy to be explicit the mapping between target and analogue must be clear, as here, where Scott spells out how workstations on a production line map onto enzymes,

"The production line analogy is a very good one. The individual 'work stations' are the enzymes, and at these molecular work stations various chemical components are brought together and fashioned into some new component of product. The product of one enzyme can then pass down the line, to become the substrate of the next enzyme, and so on until the pathway is complete."

p.147

Some analogies offer a fairly basic mapping between relatively simple systems:

"If there is lots of A around in the cell, for example, then the rate at which A tends to meet up with enzyme EAB will obviously increase (just as an increase in the number of people you happen to know entering a fairground will increase the chances of you meeting up with someone you know)."

p.150
fairgroundcell
people at a fairgroundmolecules in the cytosol
you at the fairgrounda specific enzyme in the cytosol
people entering the fairground that know you personallymolecules of a type that binds to the specific enzyme
chance of you meeting someone you knowrate of collision between enzyme and the specific molecules it binds to

An analogy with a vote counting machine

Scott compares a nerve cell, the activity of each of which is influenced by a large number of 'input' signals, to a ballot counting machine,

"…most nerve cells receive inputs, in the form of neurotransmitters, from many different cells, so the 'decision' about whether or not the cell should fire depends on the net effect of all the different inputs, some of which will be excitatory, and some inhibitory, with the pattern of input perhaps varying all the time.

So any single nerve cells acts like an [sic] tiny automatic ballot machine, assessing the number of 'yes' and 'no' votes entering it at any one time and either firing or not firing depending on which type of vote predominates at any one time.

…Nerve cells receive electrochemical signals from other cells, and each signal represents a 'yes' or a 'no' vote in an election to determine whether the cell should fire."

pp.166-8

Turnstiles in Alewife station, image from Wikimedia Commons (GNU Free Documentation License)

Scott uses the image of a turnstile, a device that blocks entry unless triggered by a coin or ticket, and which automatically locks once a person has passed through, as a familiar analogue for an ion channel into a cell. The mapping is not spelt out in detail, but should be clear to anyone familiar with turnstiles of this kind,

"When it is sitting in a polarised membrane, this protein is in a conformational state in which it is unable to allow any ions to pass through the cell. When the membrane around it becomes depolarised, however, the protein undergoes a conformational change which causes it briefly to form a channel through which Na+ ions can pass. The channel only remains open for a short time, however, since the conformational upheaval [sic] of the protein continues until it adopts a new conformation in which the passage of Na+ ions is once again blocked. The overall effect of this conformational change is a bit like the operation of a turnstile – it moves from one conformation which prevents anything from passing, into a new conformation which also prevents anything from passing, but in the process of changing from one conformation to another there is a brief period during which a channel allowing passage through is opened up."

p.163

An analogy between a sodium ion channel in a membrane, and a turnstile of the kind sometimes used to give entry to a sporting ground or transport system.

Whether there is an absolute distinction between metaphors/similes and analogies in practice can be debated. So, for example, Scott goes beyond simply suggesting that the nanoscale of molecules is like a mixing bowl, but does not offer a simple mapping between systems,

"Thermal motion turns much of the chemical microworld into a 'molecular mixing bowl' … So the solution of the cytosol acts as an all pervading chemical sea in which many of the chemicals of life are mixed together by random thermal motion as if in a molecular mixing bowl."

p.40

We could see the ocean as a simile (marked by 'acts as an') and the mixing bowl as another (marked by the scare quotes, and then 'as if in a') – but there is a partial mapping with a macroscopic mixing bowl: we are told (i) what is mixed, and (ii) the agent that mixes at the molecular scale, but it is assumed that we already know these should map to (i) the ingredients of a dish being mixed by (ii) a cook.

In places, then, Scott seems to rely on his readers to map features of analogies themselves. For example, in the following (where "The chaos of a large department store on Christmas Eve, or during the January sales, is a reasonable analogy [for the cell, as] there is order and logic within a scene of frantic and often seemingly chaotic activity"), the general point about scale was well made, but (for this reader, at least) the precise mapping remained obscure,

"The frantic chaos of chemistry proceeds too fast and too remotely for us to follow it without great difficulty. We are in the position of airborne observers who see trainloads of shoppers flowing into the city on Christmas Eve morning, and trainloads of the same shoppers laden with purchases flowing back to the suburbs in the evening. From the air we can see the overall effect of suburban shoppers 'reacting' with the shops full of goods, but we remain unaware of the hidden random chaos which allows the reaction to proceed!

p.44

Perhaps other readers immediately see this, but I am not sure what the shoppers are: molecules? but then they are unchanged by reactions? As they flow together into and out of the city (cell?) they could be ions in a nerve cell, but then what are the purchases they carry away (and have they paid for them in energy)? What are the trains? (ion channels? ribosomes?) What are the shops (mitochondria)? Perhaps I am trying to over-interpret an image that is not meant to be specific – but elsewhere Scott seems to have designed his analogies carefully to have specific mappings.

A reference to "a cofactor called 'heme' which actually acts as the chemical vessel on which the oxygen is carried"seems, by itself to be a metaphor, but when read in the context of text that precedes it, seems part of a more developed analogy:

"The most obvious system of bulk transport in the human body is the blood, which flows through our arteries, capillaries and veins like a 'river of life', bringing chemical raw materials (oxygen, water and food) to every cell of the body, and taking waste products away. Within this bulk system, however, the actual job of transporting specific substances is sometimes performed by small 'freighters' such as individual blood cells and even individual protein molecules."

p.98

The precise form of transport acting as an analogue shifts when the discussion shifts from the transport process itself to what I might refer to as the loading and unloading of the 'freighter',

"So the binding of one oxygen molecule to one subunit of an empty [sic] haemoglobin complex greatly encourages the binding of oxygen to the other three available sites. This makes the multi-subunit haemoglobin complex a bit like a four-seater car in which the first person into the car unlocks the door for another three passengers. The crucial step in loading the car is getting the first person in, after which the first person helps all the others to climb aboard.

An opposite effect occurs when loaded haemoglobin reaches a tissue in need of oxygen: the loss of one oxygen molecule from one subunit causes a conformational change in the complex which allows the other three oxygen molecules to be off-loaded much more readily. A suitable analogy to this would be an unstable four-man boat, since, if one man jumps overboard, he may rock the boat sufficiently to make the other three fall out!"

pp.100-101
Why is a child like an office block?

Child is to zygote as office building is to light bulb? (Images from Pixabay)

Scott compares the development of the child from a single cell with a self-assembling office block,

"When a human egg cell begins to divide and create a newborn child it achieves an enlargement equivalent to a lightbulb giving rise to a massive office block 250 metres high; which then, over the next 15 years or so, stretches and widens to an astounding 1,000 metres in height and nearly 250 metres across. In the 'office block' that is you all the plumbing, heating, lighting, telecommunication and ventilation systems were assembled automatically and work together smoothly to sustain a bewildering diversity of very different 'suites' and 'offices'.

p.4

Scott later revisits his office analogy, though now the building is not the growing organism, but just a single cell (one of the 'offices' from the earlier analogy?),

"Cells are not stable and unchanging structures like office blocks. Instead, most parts of a cell are in a state of continual demolition and renewal, known as 'metabolic turnover'. Imagine an office block in which a large team of builders is constantly moving through, knocking down existing walls and using the bricks to build up new ones; ripping apart the furniture and then reassembling it into new forms; peeling off wallpaper, then using it as the raw material to produce new paper which is then put back up again; and all the time some new materials are arriving through the door, to assist in the continual rebuilding, while some of the older materials are constantly being discarded out of the windows. The living cells is in a very similar siltation, with teams of enzymes constantly ripping down the structure of the cell while other teams of enzymes build it up.

… Life in the office block imagined earlier might sometimes be a little difficult and chaotic, but at least when change was required it could be brought about quickly, since the necessary tradesmen and supplies would always be on hand; and any mistakes made during the building process could always quickly be put right. Metabolic turnover bestows similar advantages on the living cell."

pp.118-119

The reference to 'teams' of enzymes is another subtle anthropomorphic metaphor. Those in a team are conscious of team membership and coordinate their activities towards a common goal – or at least that is the ideal. Enzymes may seem to be working together, but that is a just a slant we put on processes. Presumably the two sets of teams of enzymes (a catabolic set and an anabolic set) map onto the large team of builders – albeit the enzymes seem to be organised into more specialised working teams than the builders.

Some of Scott's prose, then, combines different ways of making the science familiar, as when he tells the reader

"Water, in other words, is the solvent of life, meaning that it is the liquid which permeates into all the nooks and crannies of the cell and in which all the chemical reactions of life take place. There are various small regions of the cell from which water is excluded, especially within the interior of some large molecules; but the chemistry of life largely proceeds in an ocean of water. It is not a clear ocean – thousands of different types of chemical are dissolved in it, and it is criss-crossed by a dense tangle of giant molecules which form 'fibres' or 'cables' or 'scaffolding' throughout the cell. Swimming through the cell 'cytosol' (the internal 'fluid' of the cell) would be like struggling through a dense underwater forest of seaweed, or through a thick paste or jelly, rather than darting though clear ocean."

p.6

On the molecular level, the water inside of a cell is "an ocean" (a metaphor), which can access the "nooks and crannies of the cell" (a metaphor). The ocean is interrupted by "giant molecules which form 'fibres' or 'cables' or 'scaffolding'…" These terms seem to be used as similes, marked by the use of inverted commas, although Scott also uses this convention to introduce new terms – 'cytosol' is not a simile. Presumably 'fluid' (marked by inverted commas) is being used as a simile as the cytosol is not a pure liquid, but a complex solution.

[The quote implies that "It is not a clear ocean – [as/because] thousands of different types of chemical are dissolved in it", but dissolved solutes would not stop a solution being clear: the actual ocean is very salty, with many different types of ions dissolved in it, but can be clear. Lack of transparency would be due to material suspended, but not actually dissolved, in the water.]

If this is a metaphorical ocean, it is an ocean that would be difficult to swim in, as the tangle of giant molecules is analogous to "a dense underwater forest of seaweed" so it would be like swimming trough "a thick paste or jelly".

The water cycle of life

Perhaps the pièce de résistance in terms of an analogy adopted in the book was the use of a comparison between metabolism and the water cycle,

"I have drawn an analogy between the creation of living things containing many high energy chemicals (i.e. those in which the electromagnetic force is resisted much more than it could be), and the raising water vapour from the sea into the sky. We can continue with this analogy as we look deeper into the energetics of the living cell."

pp.126-127

Scott does indeed develop the analogy, as can be seen from the quotations parsed into the table below:

target conceptanalogue
"…thermodynamic law determines that the energy of the sun must disperse out to the earth and raise the energy level of the things that are found there.
The raw materials of life are some of the things that are found there, and the energy from the sun raises these raw materials up into the higher energy levels associated with organised life,
just as
it raises water up into the sky and deposits some of it in tidy little mountain pools."
⧟
"…I have drawn an analogy between
the creation of living things containing many high energy chemicals…
and
the raising water vapour from the sea into the sky."
⧟
"The raising of water to the skies is not an isolated and irreversible event, but part of a cycle in which the water eventually loses the energy gained from the sun and returns to the earth as rain, only to absorb some more energy and be lifted up once more, and so on…
Similarly, of course,
the creation of a living being such as yourself is not an isolated and irreversible event, but is part of a cycle of life and death, of growth and decay…"
⧟
"If we look inside the chemical mechanisms of the living cell we find that they can harness the energy available in the environment, most of which ultimately comes from the sun,
in a manner similar to
the [person] who has built a water wheel, a pump, a reservoir and many secondary wheels used to power many different tasks…."
⧟
"In living things
the roles of
the water-wheels and pumps
are played by
various systems of proteins and membranes,
whilst
the the most common immediate energy reservoir is a chemical known as 'adenosine triphosphate' (ATP).
ATP is the cell's
equivalent of
water stored in a high level reservoir or a tank
because
it takes an energy input to make it, while energy is given out when it breaks apart into ADP and phosphate."
⧟
"The considerable resistance to the electromagnetic force embodied in the structure of ATP imposes a strain on the ATP molecule.
It is like
the compressed spring of a jack-in-the-box just waiting to be released;
and when it is released in some appropriate chemical reaction, then the energy level of the molecule falls as it splits up into ADP and phosphate.
Just as the force of water falling from a high gravitational energy level to a lower one can be harnessed to make various energy-requiring processes proceed,
so
the force of an ATP molecule falling from a high chemical energy level to a lower one can be harnessed to make a wide variety of energy-requiring chemical reactions proceed…"
⧟
"The ATP manufacturing enzyme
is closely analogous to
a water-wheel,
for
as the hydrogen ions are allowed to flow back through the enzyme,
just as
water flows over a water-wheel,
so
the ensuing chemical reactions 'lift up' the precursors of ATP into their high energy ATP state."
⧟
"The principle of such energy coupling
can be understood by the simple analogy of
the water flowing downhill over a water-wheel, and thus serving to turn the wheel and, for example, raise some weight from the ground using a pulley."
⧟
"These proteins are the molecular machines
which take the place of
the water-wheels and ropes and pulleys which can couple the falling of water down a mountainside to the lifting of some weight beside the stream"
An extended analogy between two systems

Whether this should be seen as one extended analogy, or more strictly as several, somewhat distinct but related, comparisons is moot, as becomes clear when trying to map out the different features. My best attempt involved some duplication and ambiguity. (Hint to all designers of teaching analogies – map them out as parallel concept maps to help you visualise and keep track of the points being made.)

An analogy (or set of analogies) between biological/biochemical and physical systems

Visualisation – mental simulation

Teaching analogies usually link to what is expected to be (for the members of the audience) a familiar situation, experience, or phenomenon. Readers will be familiar with an office block, or swimming in water.

However, it is also possible for the science communicator to set up an analogy based on a scenario which is unlikely to be familiar, but which can be readily imagined by the reader.

"To appreciate the power of random motion to bring about seemingly purposeful change, imagine a room full of blindfolded people all instructed to walk about at random 'bouncing' off the walls and one another. Imagine also that they have been told to stop moving only when they bump into a small picture hanging from a wall. Finally, suppose that all the pictures are hung in a second room, linked to the room full of people by a narrow open doorway…"

p.40

Few if any readers will have been familiar with this scenario, but the components – groups of people in rooms, blindfolding, adjoining rooms, pictures hung on walls – are all familiar and there is nothing inherently problematic about the scenario even it does not seem very likely. So, here the reader has to build up the analogy from a number of familiar but distinct images.

So, we might consider this a kind of 'gedankenexperiment' or thought experiment – the reader is prompted to consider what would happen if…(and then to transfer what would happen to the target system at the molecular scale). Perhaps some readers immediately 'see' (intuit) what happens in this situation, but otherwise they can 'run' a mental simulation to find out – a technique scientists themselves have used (if probably not regarding blindfolded people in picture galleries).

Analogies only reflect some aspects of the target being compared. The features that map unproblematically are known as the positive analogy, but there is usually a negative analogy as well: features that do not match, and so which would be misleading if carried across. Realistically, the negative analogy will usually have more content than the positive analogy, although much of the negative analogy will be so obviously irrelevant that it is unlikely to confuse anyone.

So, for example, in the analogy the blindfolded people will be wearing clothes, may exchange apologies (or curses) on bumping into each other, and will likely end up bruised – and human nature being what it is, some may cheat by sneaking a look past the edge of the blindfold – but no reader is likely to think these are features that transfer across to the target! Perhaps, however, a reader might wonder if the molecules, like the blindfolded people, are drawing on a source of energy to keep up the activity, and would tire eventually?

There are some other potentially more problematic aspects of the negative analogy. In the thought experiment, the people have been given instructions about what to do, and when to stop, and are acting deliberately. These features do not transfer across, but a reader might not realise this, and could therefore understand the analogy anthropomorphically. It is in situations like this where the teacher can seek feedback on how the analogy is being interpreted (that is, use informal formative assessment), but an author of a book loses control once the manuscript is completed.

Molecular mechanisms made familiar?

There is nothing unusual in Scott's use of metaphor, simile and analogy in seeking to help readers understand abstract scientific ideas. This is an approach common to a good deal of science communication, within and beyond formal teaching. Vital Principles offers many examples, but such devices are common in books seeking to explain science.

I did raise two questions about these techniques above. How do we know if these comparisons are effective in communicating the science? To find out, we would need to talk to readers and question them about their interpretations of the text.

In formal science teaching the focus of such research would likely be the extent to which the presentation supported a learner in acquiring a canonical understanding of the science.

However, as I suggested above, if such research concerned popular science books, we might ask whether the purpose of such books is to teach science or satisfy reader interest. Thus, above, I distinguished an objective and a subjective aspect. If a reader selected a book purely for interest, and is satisfied by what they have read – it made sense to them, and satisfied their curiosity – then does it matter if they may have not understood canonically?

When I read such texts, I wonder about both how a general readership responds to the comparisons offered by authors to make the unfamiliar familiar, and what sense the readers come away with of the science. I guess to some extent popular science authors at least get some level of feedback on the former question – if readers come back for their other titles, then they must be doing something right.

I thought Scott showed a good deal of ingenuity and craft in setting out an account of a challenging and complex area of science – but I would love to know how his different readers interpreted some of his comparisons.

Work cited:
Notes:

1 I have picked up a good many 'popular science books' over the years, but quite a few of them got put on the shelves till I had time to engage with them in any depth. Other things usually got in the way – lesson/lecture preparation being the most demanding imperative for soaking up time over my 'working' life. Retirement has finally allowed me to start going through the shelves…

2 In the English context, perhaps elsewhere, the textbook is now also often expected to not only cover the right content, but follow the examination board's line on the level of treatment, even to the degree of what is acceptable phrasing. Indeed, there are now textbooks associated with the different exam board syllabuses for the 'same' qualification (e.g., A level Chemistry). This seems very unhealthy, and come the revolution…

3 The model I am referring to here is the mental model in the teacher's mind of the learner or reader – the background knowledge they have available, their existing level of understanding, the sophistication of their thinking, the range of everyday references they are familiar with which might be useful in making comparisons, their concentration span for dealing with new material or complex language …

If we think of teaching-learning as a system, many system failure (failures of students to understand teaching as intended) can be considered to be due to a mismatch – the teacher's mental model is inaccurate in ways that leads to non-optimal choices in presenting material (Taber, 2001 [Download article]).

This is the basis of the 'learning doctor' approach.

Read about Science learning doctors

4 This is the crux of the so called 'constructivist' perspective on teaching science – a perspective discussed in depth elsewhere on the site.

Read about constructivism

5 There was little in the book I really would have argued with. However, there were a few questionable statements:

"Yet this apparent miracle is completed thousands of times each day throughout the world [in humans], and similar miracles create all manner of simpler creatures, from elephants and birds and flies to bacteria and flowers and mighty oaks."

p.5

This statement seemed to reflect the long-lasting notion of nature as a 'great chain of being' with humans (in the middle of the chain, below a vast range of angelic forms, but) top of the natural world. Bacteria are simpler than humans, I would acknowledge; but I am less sure about flies; even less sure about birds; and question considering trees and other flowering plants, or elephants, as (biologically) simpler than us. This seems an anthropocentric (human-centred), rather than a scientific, take.

"…the periodic table… lists the 92 naturally occurring atoms (plus a few man-made ones) which are the basic raw materials of chemistry…"

p.19

There are clearly more than 92 naturally occurring atoms in the universe. I believe we think there are 90 naturally occurring elements. That is 90 "naturally occurring [kinds of, in the specific sense of proton number] atoms".

Similarly, "a 'compound' is any chemical [sic] composed of two or more atoms chemically bonded together" (pp.29-30) would imply that H2, C60, N2, O2, F2, P4, S8, Cl2, etc are all compounds (when these are elements, not compounds).

Another slightly questionable suggestion was that

"…electrons appear to surround the atomic nucleus, but in a way that allows them to dart to and fro in a seemingly chaotic manner within a particular region of space."

p.21

The notion of electrons darting back and forth does not really reflect the scientific model, but the orbital/quantum model of the atom is subtle and difficult to explain, and was not needed at the level of the description being presented.

A more obvious error was that

"…'heat' is just a measure of the kinetic energy with which particles of matter are moving…"

p.26

In physics, the temperature of a material is considered to reflect the average kinetic energy of the particles (e.g., molecules). But heat is a distinct concept from temperature. Heat is the energy transferred between samples of matter, due to a difference in temperature. So, when Scott writes

"We all know that heat energy moves inevitably from hot places to cold places, and that it will never spontaneously move in the opposite direction."

p.32

this could be seen as a tautology: like saying that imports always come into the county rather than leave – because of how imports are defined.

Although heat and temperature are related concepts, confusing or conflating them is a common alternative conception found among students. Confusing heat with temperature is like confusing a payment into your bank account with the account balance.

Moreover, Scott uses the wrong term when writes,

"[The molecules of?] Chemicals come into contact with one another because they are all constantly moving with the energy we call heat."

p.191

This internal energy that substances have due to the inherent motion of their particles is not heat – it is present even when there is a perfectly uniform temperature throughout a sample (and so no heating going on).

Scott tells readers that "Another name for … a voltage difference is a 'potential difference'…" (p.162) but the term voltage (not voltage difference) normally refers to a potential difference, p.d.. (So, the term voltage difference implies a difference between potential differences, not a difference in potential. If you had one battery with a p.d. across its terminals of 6.0V, and another with a p.d. across its terminals of 4.5V, you could say the 'voltage difference' between the batteries was 1.5V.)

A common alternative conception which Scott seems to share, or at least is happy to reinforce, is the 'fairy tale'* of how ionic bonding results from the transfer of an electron from a metal atom to a neutral non-metal atom,

"When sodium atoms react with chlorine atoms electrons are actually transferred from one atom to the other (see figure [which shows electron transfer from one atom to another]). One electron which is relatively loosely held by a sodium atom can move over to become attached to a chlorine atom."

p.30

This describes a chemically very unlikely scenario (neither sodium nor chlorine are found in the atomic state under normal conditions on earth), and if a sodium atom were to somehow collide with a chlorine atom, the process Scott describes would be thermodynamically non-viable – it requires too much energy to remove even the outermost 'relatively loosely held' electron from the neutral sodium atom. Perhaps this is why in the school laboratory NaCl tends to be prepared from solutions that already contain the sodium ions [NaOH(aq)] and the chloride ions [HCl(aq)].

* For example, read 'A tangible user interface for teaching fairy tales about chemical bonding'

It is hard to be too critical of Scott here, as this account is found in many chemistry text books (and I have even seen it expected in public examinations) although from a scientific point of view, it is a nonsense. That many learners come to think that ionic bonding is due to (or even, 'is') a process of electron transfer is surely a pedagogic learning impediment (Taber, 1994) – a false idea that is commonly taught in school chemistry.

Read more about common misconceptions of ionic bonding

6 As the author of a paper called ' Mediating mental models of metals: acknowledging the priority of the learner's prior learning', I must confess to being somewhat partial to some decent alliteration.

7 Many scientists will believe there is a purpose underpinning the evolution of life on earth, and will see creation as the unfolding of a supernatural plan. (Some others will vehemently reject this. Others still will be agnostic.) However, natural science is concerned with providing natural explanations of the world in terms of natural mechanisms. Even if a scientist thinks things are the way they are because that is God's will, that would be inadmissible as a scientific argument, as it does not explain how things came about through natural processes.

Read more about science and religion

8 Teaching, or for that matter writing a science book, is informed by the teacher's/author's mental model of how the reader/listener will make sense of the text (see above). How they actually make sense of the text depends on the interpretive resources they have available, and bring to mind, and it is common for learners/readers not to interpret texts in the way intended – often they either do not make sense of the information, or make a different sense to that intended. A teacher who is a 'learning doctor' can seek to diagnose and treat these 'teaching-learning system failures' when they inevitably occur, but teachers can avoid a good many potential problems by being as explicit as possible and not relying on learners to spontaneously make intended associations with prior learning or cultural referents.

Read about being a learning doctor

As suggested above, authors have an even more challenging task as their readerships may have a diverse range of prior knowledge and other available interpretive resources (e.g., a popular television programme or pop star in one country may be unknown to readers from another); and the author cannot check they have been understood as intended, in the way a teacher usually can.

Creeping bronzes

Evidence of journalistic creep in 'surprising' Benin bronzes claim

Keith S. Taber

How certain can we be about the origin of metals used in historic artefacts? (Image by Monika from Pixabay)

Science offers reliable knowledge of the natural world – but not absolutely certain knowledge. Conclusions from scientific studies follow from the results, but no research can offer absolutely certain conclusions as there are always provisos.

Read about critical reading of research

Scientists tend to know this, something emphasised for example by Albert Einstein (1940), who described scientific theories (used to interpret research results) as "hypothetical, never completely final, always subject to question and doubt".

When scientists talk to one another within some research programme they may used a shared linguistic code where they can omit the various conditionals ('likely', 'it seems', 'according to our best estimates', 'assuming the underlying theory', 'within experimental error', and the rest) as these are understood, and so may be left unspoken, thus increasing economy of language.

When scientists explain their work to a wider public such conditionals may also be left out to keep the account simple, but really should be mentioned. A particular trope that annoyed me when I was younger was the high frequency of links in science documentaries that told me "this could only mean…" (Taber, 2007) when honest science is always framed more along the lines "this would seem to mean…", "this could possibly mean…", "this suggested the possibility"…

Read about scientific certainty in the media

Journalistic creep

By journalistic creep I mean the tendency for some journalists who act as intermediates between research scientists and the public to keep the story simple by omitting important provisos. Science teachers will appreciate this, as they often have to decide which details can be included in a presentation without loosing or confusing the audience. A useful mantra may be:

Simplification may be necessary – but oversimplification can be misleading

A slightly different type of journalist creep occurs within stories themselves, Sometimes the banner headline and the introduction to a piece report definitive, certain scientific results – but reading on (for those that do!) reveals nuances not acknowledged at the start. Teachers will again appreciate this tactic: offer the overview with the main point, before going back to fill in the more subtle aspects. But then, teachers have (somewhat) more control over whether the audience engages with the full account.

I am not intending to criticise journalists in general here, as scientists themselves have a tendency to do something similar when it comes to finding titles for papers that will attract attention by perhaps suggesting something more certain (or, sometimes, poetic or even controversial) than can be supported by the full report.

An example of a Benin Bronze (a brass artefact from what is now Nigeria) in the British [sic] Museum

(British Museum, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons)

Where did the Benin bronzes metal come from?

The title of a recent article in the RSC's magazine for teachers, Education in Chemistry, proclaimed a "Surprise origin for Benin bronzes".1 The article started with the claim:

"Geochemists have confirmed that most of the Benin bronzes – sculptured heads, plaques and figurines made by the Edo people in West Africa between the 16th and 19th centuries – are made from brass that originated thousands of miles away in the German Rhineland."

So, this was something that scientists had apparently confirmed as being the case.

Reading on, one finds that

  • it has been "long suspected that metal used for the artworks was melted-down manillas that the Portuguese brought to West Africa"
  • scientists "analysed 67 manillas known to have been used in early Portuguese trade. The manillas were recovered from five shipwrecks in the Atlantic and three land sites in Europe and Africa"
  • they "found strong similarities between the manillas studied and the metal used in more than 700 Benin bronzes with previously published chemical compositions"
  • and "the chemical composition of the copper in the manillas matched copper ores mined in northern Europe"
  • and "suggests that modern-day Germany, specifically the German Rhineland, was the main source of the metal".

So, there is a chain of argument here which seems quite persuasive, but to move from this to it being "confirmed that most of the Benin bronzes…are made from brass that originated …in the German Rhineland" seems an example of journalistic creep.

The reference to "the chemical composition of the copper [sic] in the manillas" is unclear, as according to the original research paper the sample of manilla analysed were:

"chemically different from each other. Although most manillas analysed here …are brasses or leaded brasses, sometimes with small amounts of tin, a few specimens are leaded copper with little or no zinc."

Skowronek, et al., 2023

The key data presented in the paper concerned the ratios of different lead isotopes (205Pb:204Pb; 206Pb:204Pb; 207Pb:204Pb; 208Pb:204Pb {see the reproduced figure below}) in

  • ore from different European locations (according to published sources)
  • sampled Benin bronze (as reported from earlier research), and
  • sampled recovered manillas

and the ratios of different elements (Ni:AS; Sb:As; Bi:As) in previously sampled Benin bronzes and sampled manillas.

The tendency to consider a chain of argument where each link seems reasonably persuasive as supporting fairly certain conclusions is logically flawed (it is like concluding from knowledge that one's chance of dying on any particular day is very low, that one must be immortal) but seems reflected in something I have noticed with some research students: that often their overall confidence in the conclusions of a research paper they have scrutinised is higher than their confidence in some of the distinct component parts of that study.

An example of a student's evaluation of a research study

This is like being told by a mechanic that your cycle brakes have a 20% of failing in the next year; the tyres 30%; the chain 20%; and the frame 10%; and concluding from this that there is only about a 20% chance of having any kind of failure in that time!

A definite identification?

The peer reviewed research paper which reports the study discussed in the Education in Chemistry article informs readers that

"In the current study, documentary sources and geochemical analyses are used to demonstrate that the source of the early Portuguese "tacoais" manillas and, ultimately, the Benin Bronzes was the German Rhineland."

"…this study definitively identifies the Rhineland as the principal source of manillas at the opening of the Portuguese trade…"

Skowronek, et al.,2023

which sounds pretty definitive, but interestingly the study did not rely on chemical analysis alone, but also 'documentary' evidence. In effect, historical evidence provided another link in the argument, by suggesting the range of possible sources of the alloy that should be considered in any chemical comparisons. This assumes there were no mining and smelting operations providing metal for the trade with Africa which have not been well-documented by historians. That seems a reasonable assumption, but adds another proviso to the conclusions.

The researchers reported that

Pre-18th century manillas share strong isotopic similarities with Benin's famous artworks. Trace elements such as antimony, arsenic, nickel and bismuth are not as similar as the lead isotope data…. The greater data derivation suggests that manillas were added to older brass or bronze scrap pieces to produce the Benin works, an idea proposed earlier.

and acknowledges that

Millions of these artifacts were sent to West Africa where they likely provided the major, virtually the only, source of brass for West African casters between the 15th and the 18th centuries, including serving as the principal metal source of the Benin Bronzes. However, the difference in trace elemental patterns between manillas and Benin Bronzes does not allow postulating that they have been the only source.

The figure below is taken from the research report.

Part of Figure 2 from the open access paper (© 2023 Skowronek et al. – distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The chart shows results from sampled examples of Benin bronzes (blue circles); compared with the values of the same isotope ratios from different copper ore site (squares) and manillas sampled from different archaeological sties (triangles).

The researchers feel that the pattern of clustering of results (in this, and other similar comparisons between lead isotope ratios) from the Benin bronzes, compared with those from the sampled manillas, and the ore sites, allows them to identify the source of metal re-purposed by the Edo craftspeople to make the bronzes.

It is certainly the case that the blue circles (which refer to the artworks) and the green squares (which refer to copper ore samples from Rhineland) do seem to generally cluster in a similar region of the graph – and that some of the samples taken from the manillas also seem to fit this pattern.

I can see why this might strongly suggest the Rhineland (certainly more so than Wales) as the source of the copper believed to be used in manillas which were traded in Africa and are thought to have been later melted down as part of the composition of alloy used to make the Benin bronzes.

Whether that makes for either

  • definitive identification of the Rhineland as the principal source of manillas (Skowronek paper), or
  • confirmation that most of the Benin bronze are made from brass that originated thousands of miles away in the German Rhineland (EiC)

seems somewhat less certain. Just as scientific claims should be.

A conclusion for science education

It is both human nature, and often good journalistic or pedagogic practice to begin with a clear, uncomplicated statement of what is to be communicated. But we also know that what is heard or read first may be better retained in memory than what follows. It also seems that people in general tend to apply the wrong kind of calculus when there are multiple source of doubt – being more likely to estimate overall doubt as being the mean or modal level of the several discrete sources of doubt, rather than something that accumulates step-on-step.

It seems there is a major issue here for science education in training young people in critically questioning claims, looking for the relevant provisos, and understanding how to integrate levels of doubt (or, similarly, risk) that are distributed over a sequence of phases in a process.

All research conclusions (in any empirical study in any discipline) rely on a network of assumptions and interpretations, any one of which could be a weak link in the chain of logic. This is my take on some of the most critical links and assumptions in the Benin bronzes study. One could easily further complicate this scheme (for example, I have ignored the assumptions about the validity of the techniques and calibration of the instrumentation used to find the isotopic composition of metal samples).

Work cited:
Note:

1 It is not clear to me what the surprise was – but perhaps this is meant to suggest the claim may be surprising to readers of the article. The study discussed was premised on the assumption that the Benin Bronzes were made from metal largely re-purposed from manillas traded from Europe, which had originally been cast in one of the known areas in Europe with metal working traditions. The researchers included the Rhineland as one of the potential regional sites they were considering. So, it was surely a surprise only in a similar sense to rolling a die and it landing on 4, rather than say 2 or 5, would be a surprise.

But then, would you be just as likely to read an article entitled "Benin bronzes found to have anticipated origin"?

Explaining Y T cells stop working

Communicating oncology research

Keith S. Taber

…to the best of my knowledge, there is absolutely no reason to suspect that Prof. Theodorescu falsified his academic credentials…

The following text is an extract from a podcast item reporting recently published research into bladder cancer:

"The Y-negative cells cause an immune evasive environment in the tumour, and that, if you will, paralyses, the T cells, and exhausts them, makes them tired and ineffective, and this prevents the Y-negative tumour from being rejected, therefore allowing it to grow much better."

"Exhausted T cells have lost their ability to kill cancer cells, and have lots of proteins on their surface known as checkpoints, which put the brakes on immune responses.

But this exhausting environment made by the tumours could actually be their undoing"

"What they also did, inadvertently I'm sure, is made themselves a lot more vulnerable to one of the most useful and prevalent therapeutics in cancer today, which is immune checkpoint inhibitors."

"Immune checkpoint inhibitors are a class of drugs that block those checkpoint proteins that sit on the surface of T cells, effectively taking the brakes off immune responses, causing T cells to become more aggressive."

Dan Theodorescu & Nick Petrić Howe speaking on the Nature Podcast

Prof. Dan Theodorescu MD, PhD, is the Director of the Samuel Oschin Comprehensive Cancer Institute at Cedars-Sinai, Professor of Surgery, Pathology and Laboratory Medicine; and corresponding author on the paper (Abdel-Hafiz et al., 2023) published in Nature, and discussed in the podcast.

Nick Petrić Howe, Senior Multimedia Editor at Nature Research, was the journalist presenting the item on the podcast.

Communicating science

Scientific research is communicated to other specialist scientists through research reports which reflect a particular genre of writing, and are written with specialist researchers in the same field as the main target readership. Such reports are usually of a quite technical nature, and (appropriately) assume that readers will have a high level of prior understanding of concepts in the field and the technical language used. Such tropes as simile and analogy certainly can sometimes feature, but generally figurative language is kept to a minimum.

Communication to a wider audience of people with a general interest in science needs to adopt a different register. As I have noted on this site before, this is quite challenging as a general public audience is likely to be very diverse in terms of its level of knowledge and understanding of background to any scientific research. Perhaps that is why as a former teacher (and so a science communicator that could make reasonably informed assumptions about the background of my audience in any particular lesson) I find the language of this type of science dissemination fascinating.

Read about science in public discourse and the media

The gist

The study discussed in the podcast reported on a line of research exploring the genomics of bladder cancer, and in particular how tumours that develop from cells that have deficiencies in the Y chromosome seem to have particular characteristics.

Put simply, tumours of this kind were likely to be inherently more damaging to the patient, although also likely to be more responsive to an existing class of medicines. (At this stage the work has largely relied on in vitro studies and 'animal models' (mice) so the implications for actual human cancer patients are reasonable, but speculative.)

The language used

The short extract of the dialogue I have transcribed above seems quite 'dense' in interesting language when de-constructed:

Y-negative cells – a new technical term?

The extract starts with reference to Y-negative cells. Earlier in the item it had been explained that some cells have no Y chromosome, or an incomplete Y chromosome. (For someone to understand this information, they would need to have some background knowledge relating to what chromosomes are, and why they are important in cells. 1 ) The term Y-negative cell therefore, given that context, refers to a cell which lacks the usual Y chromosome. 2 If such a cell turns cancerous it will give rise to a tumour which is Y-negative (as all the tumour cells are formed from the division of that cancerous cell). The published report notes "Loss of the Y chromosome (LOY) is observed in multiple cancer types, including 10-40% of bladder cancers" (Abdel-Hafiz et al., 2023), an observation which motivates the area of research.

An immune evasive environment?

The word 'evasion' appears in the title of the paper. To evade something means to avoid it, which might suggest a sense of deliberation. Immune evasion is a recognised issue, as in cancers "interactions between the immune system and the tumour occur through complex events that usually eventually climax either in successful tumour eradication or immune evasion by the tumour" (Vinay et al., 2015): that is, either the immune system destroys the cancer, or the cancer is able to grow due to some mechanism(s) that prevent the immune system killing the tumour cells. The 'immune evasive environment' then refers to the environment of the tumour's cells in a context where aspects of the normal immune mechanisms are inoperative or restricted.

Paralysed, exhausted and tired T cells

T cells are one of the classes of cell that make up the immune system, and the item was suggesting that with 'LOY' the T cells are unable to function in the way they normally do when interacting with cancer cells that have an intact Y chromosome. ('LOY' is the acronym for a process, viz., "loss of the Y chromosome", but once defined can be used in a way that reifies LOY as if it refers to an object. 3 In "…with 'LOY'…", I am treating LOY as a medically diagnosable condition.)

Are the T cells paralysed? That normally means not able to move, which is not the case here. So 'paralysed' seems to be used as a metaphor, a way of 'making the unfamiliar familiar' for a non specialist audience. A large part of the task of a science teacher is to make the unfamiliar [become] familiar to learners.

Read about making the unfamiliar familiar

Actually, I would better class this specific use as a simile rather than a metaphor:

"The Y-negative cells cause an immune evasive environment in the tumour, and that, if you will, paralyses, the T cells"

A simile in poetic language normally refers to something being 'like' or 'as' something else, as when the star Betelgeuse was said to be "like an imbalanced washing machine tub" or a laser was described as being used as a "kind of spark plug". Here, Prof. Theodorescu marks the term 'paralyses' with 'if you will' in a similar way to how when selection theory has been said to be "like a Tibetan prayer-wheel…" the word 'like' marks that this is noting a similarity, not an identity (selection theory is not suggested to be a prayer-wheel, but rather to be in some way like one).

Read examples of similes used in discussing science

The T cells were said to be as if paralysed, but they were also exhausted and tired. Yet, again, 'exhausted' does not seem to be meant literally. The T cell has not used up its supply of something (energy, or anything else), so this is another metaphor. 'Tired' can be seen as synonymous to exhausted, except usually 'tired' refers to a subjective experience. The T cells are not sentient and presumably do not feel tired – so, this is another metaphor; indeed an anthropomorphic metaphor, as it refers to the cells as though they have subjective experience like a person.

Read examples of metaphors used in discussing science

Hey, you immune cells – are you feeling tired? How about taking a break, and doing some stretching exercises and a little yoga?

Images from Pixabay

Anthropomorphism is a common trope in science discourse, especially in biological contexts. It can sometimes help communication of abstract material to present scientific phenomena in a narrative that relates to human subjective experience – perhaps referring to disease 'evading' the immune system – but consequently often gets adopted into in students' pseudo-explanations (e.g., the reaction happened because the atom wanted another electron, the gas expands because the molecules wanted more space). 4

Read about types of pseudo-explanations

Read examples of anthropomorphism in science discourse

Yet the term 'exhausted' also appears in the published research report ("Ylow bladder cancers contained a higher proportion of exhausted and progenitor exhausted CD8+ T cells..."). So, this is a term that is being adopted into the terminology of the research field. A paper from 2019 set out to define what this means: "'T cell exhaustion' is a broad term that has been used to describe the response of T cells to chronic antigen stimulation, first in the setting of chronic viral infection but more recently in response to tumours" (Blank, et al., 2019). Another study notes that

"It is now clear that T cells are not necessarily physically deleted under conditions of antigen persistence but can instead become functionally inept and incapable of elaborating the usual array of effector activities typically associated with robust, protective, effector and memory T-cell populations."

Yi, Cox, & Zajac, 2010

It is not unusual for terms that seem to be initially used metaphorically, to become adopted in a scientific field as technical terms (such as the 'birth' and 'death' of stars in astronomy). Indeed, inept seem to me a term that is normally applied to people who have agency and can learn skills, but lack skill in an area where the are active. The field of oncology seems to have adopted the notion of ineptitude, to label some T cells as 'inept'.

Unlike in human hereditary, where we would not assume a child can directly inherit a lack of skill in some area of activity from its parents (there is no gene for playing chess, or spraying cars, or heart surgery, or balancing account books), at the cellular level it is possible to have "inept T-cell lineages" (Fredholm et al, 2018). If one is going to anthropomorphise cells, then perhaps 'inept' is an unfair descriptor for structural changes that modify functionality, and can be passed on to 'daughter' cells: should these cells be considered to have a disability rather than be inept? For that matter, an exhausted T-cell seems to have more in common with a metamorphosed caterpillar than an exhausted marathon runner.

Rejection – a dead metaphor?

'Rejection' is a technical terms used in medical science for when the immune system 'attacks' something that it 'identifies' as not self: be that a tumour or a transplanted tissue. Note that here terms such as 'attacks' and 'identifies' are really also anthropomorphic metaphors to label complex processes and mechanisms that we gloss in human terms.

What actually happens is in effect some chemistry – there is nothing deliberate about what the cancer cells or the immune cells are doing. Tumours that grow quickly are described as 'aggressive' ("…causing T cells to become more aggressive") another term that might be understood as an anthropomorphic metaphor, as aggression normally refers to an attitude adopted. The tumour cells are just cells that grow and divide: they have no attitude nor intentions, and do not deliberately harm their host or even deliberately divide to grow the cancer.

When the term 'rejection' was first suggested for use in these contexts it will have been a metaphor itself, a word transplanted [sic] from one context where it was widely used to another novel context. However, the 'transplant took' (rather than being 'rejected'!) and came to be accepted as having a new biological meaning. Such a term is sometimes called a dead metaphor (or a clichéd metaphor) as it has lost its metaphorical status, and become a technical term. Tumours are now literally rejected. And T cells do now become exhausted (and inept). And tumours can now be aggressive.

Within the specialist field, such words now have nuanced technical meanings, related to, but subtly different from, their source words' usage in general language. Experts know that – but lay people may not always realise. Strictly, the words aggressive in 'an aggressive drunk' and 'an aggressive tumour' are homonyms.

Seated checkpoints: quo vardis, friend or foe?

The same is the case with 'checkpoints'. Referring to proteins on the immune cell surface that interact with proteins on tumour cells, the label 'checkpoints' will have been a metaphorical transplant of an existing term (as in border checkpoints, where it is checked that someone's papers are in order for entry to a country); but, now, this is accepted usage.

T cells are able to destroy other cells. However, they have proteins on their surfaces which can bind to proteins on other cells, and when these are bound the T cells do not destroy the other cells. (Do these proteins really "sit on the surface of T cells" – or is sitting an action only available to organisms with certain types of anatomic features – such as buttocks and jointed legs perhaps? So, this is another metaphor, but one that conveys meaning so readily that most listeners will not have noticed it. 6 )

So, immune cells have evolved because they 'protect' the organism from 'foreign' cells, and the checkpoints have evolved because they prevent the immune cells destroying cells from the same individual organism. 5 This works to the extent that the binding of the checkpoints is specific. Tumour cells (which are derived from the individual) can sometimes bind, and so the T cells may be ineffective in destroying them. Immune checkpoint inhibitors can interfere with the mechanism by which tumour cells act on the T cells as 'self' cells – something sometimes referred to as a checkpoint 'blockade' (yet another metaphor) – something represented in the following image:

Figure entitled "Immune checkpoint blockade for T-cell activation" (note the 'exhausted' T cells) (Fig. 2, from Darvin, et al., 2018. Open access under http://creativecommons.org/licenses/by/4.0/). [There is an interesting mix of iconic (cell shapes) and symbolic (e.g., lightning strikes?) signs in the figure.]

The extract of dialogue quoted above suggests that the checkpoints "put the brakes on immune responses". There are of course no actual brakes, so this is again metaphorical. However, we might consider 'putting the brakes' on as having become an English idiom, that is, the term is now widely understood as applying to any situation where a process is brought to a stop, regardless of whether or not there are actual brakes involved. A raise in bank interest rates might be said to be intended to put the brakes on inflation. (Indeed, as my O level economics teacher at North Romford Comp. habitually explained managing the economy in terms of driving a car – which of course we were all too young to legally have experienced – he may well have actually said this.)

Can tumours behave advertently?

At one point Prof. Theodorescu, suggested that "what [the tumours] also did, inadvertently I'm sure, is made themselves a lot more vulnerable to one of the most useful and prevalent therapeutics in cancer today". I am also sure that this effect was inadvertent. Otherwise, the tumour acted advertently, which would mean it behaved deliberately with this outcome in mind.

It clearly would not seem to be in a tumour's interest to make itself more susceptible to therapeutics, but then agents do sometimes behave in ways that seem irrational to others – for example, because of bravado. So, I do not rule out apparently self-destructive behaviour from being deliberate (as I drafted this piece, the news broadcast reports on an apparent coup attempt in Russia, suggesting that a few tens of thousands of men are looking to take over a nation of over 140 million that had been paying them to fight in the illegal invasion of Ukraine). Rather, my reason for being sure this not deliberate, is that I do not think that a tumour is the kind of entity that can behave advertently. 7

So, I do not disagree with Prof. Theodorescu, but I do think that stating that, in this case, the behaviour was inadvertent seems to imply that that a tumour can in some circumstances act deliberately (i.e., anthropomorphism, again). I am sure that was not the intention, but it seems, inadvertently I'm sure, to reflect the tactic of conspicuously stating someone is not guilty of some act as a means of starting a contrary rumour.

So, I would like to make it absolutely clear, without any sense of ambiguity, that, certainly to the very best of my knowledge, there is absolutely no reason to suspect that Prof. Theodorescu falsified his academic credentials using red crayons and recycled cereal packets.

Work cited:
Notes:

1 Any communication of science will inevitably have to assume some background. In teaching, we can use conceptual analysis to break down any topic and identify pre-requisite prior knowledge that will be needed before introducing new information. Science education builds up understanding slowly over many years, 'building on' what learners have already been taught. Anyone asked to give an account or explanation to a general audience has to make an informed judgement of where it is reasonable to start.

2 It might seem that the cells of females are 'Y-negative' as these do not usually contain Y chromosomes. However, from the context (the discussion of loss of, or incomplete, Y-chromosomes) the term is being used to refer to cells with no Y chromosomes that derived ultimately (by imperfect copying) from a cell which did have a Y chromosome. That is, this is a feature of tumours in men.

Although women do not (usually) have Y chromosomes, it is sometimes suggested that the man's Y chromosome can be considered an incomplete X chromosome, so in a sense all men might be considered as incomplete, imperfect women, as some readers might have long suspected.

3 This is not meant as some kind of criticism, but rather an observation on one of the affordances of language in use. It is very useful for the scientist to package up an idea (here, the loss of the Y chromosome from a cell's set of nuclear chromosomes) in a new term or acronym, which can then be put to work as a neologism, thus simplifying sentence structure. The reader then needs to decode this new term in various contexts. That is perfectly reasonable within the genre of research reports (as this only adds minimally to the interpretative load of a specialist reader who is likely to have strong enough background to have capacity to readily make sense of the new term in various contexts). So, in the published paper (Abdel-Hafiz, 2023), we find, inter alia,

  • "…LOY correlates with…"
  • "…naturally occurring LOY mutant bladder cancer cells…"
  • "In ageing men, LOY has been associated with many adverse health consequences."
  • "…cancer cells with LOY…"
  • "…mouse tumours with LOY…"
  • "…human bladder cancer specimens with LOY…"
  • "…LOY is present early in disease progression…"
  • "…the lack of Y chromosome gene expression in the MB49 sublines was due to LOY"
  • "…the important role of these two genes in conferring the LOY phenotype…"
  • "…patients with LOY had a reduced overall survival following surgery…"
  • "…tumours with LOY grew more aggressively…"
  • "…the mechanism of LOY-driven tumour evasion…"

There is even a case of LOY being taken as a sufficiently familiar to be compounded into a further acronym, 'MADLOY':

"we used TCGA DNA sequencing data and mosaic alteration detection for LOY (MADLOY) to detect LOY".

4 Unfortunately, thinking anthropomorphically about viruses, cells, molecules, etc., can become a habit of mind. Students may come to see such anthropomorphisms as having the status of genuine scientific explanations (that they can use in exams, for example). Therefore, care is needed with using anthropomorphism in science teaching (Taber & Watts, 1996).

Read about anthropomorphism and science learning

5 So, we might suggest that

  • 'checkpoints' is a recently deceased metaphor, with its new meaning only familiar in the technical language community of oncologists and cognate specialists, whereas
  • 'sits' is a long dead metaphor as its broader meaning is likely to be understood widely within the natural language community of English speakers.

6 My use of 'because' is not to be read in a teleological sense as

  • immune cells have evolved in order to protect the organism from 'foreign' cells
  • the checkpoints have evolved in order to prevent the immune cells destroying cells form the same individual organism

Rather in the sense of the reason something has evolved is because it has a property that offers an advantage, and so was selected for:

  • immune cells have evolved because they were selected for because they protect the organism from 'foreign' cells
  • the checkpoints have evolved because they were selected for because they prevent the immune cells destroying cells from the same individual organism

7 I am making an 'ontological judgement'. I might say I am doing ontology. In my teaching of graduate students I found some were wary of terms like ontology and epistemology, but actually I would argue that we all 'do ontology' every time we make a judgement about the kind of entity something is (and we do epistemology every time we make a judgement about the likely truth value of some claim).

If you judge that fairies are imaginary or that dinosaurs are extinct, I suggest that you are doing ontology. For that matter, if you judge that fairies and dinosaurs are alive and well, and live at the bottom of your garden, then you are also doing ontology – if perhaps not so well.

Read about ontology

Who has the right to call someone 'White'?

Science cannot tell us

Keith S. Taber (him/his…and White?)

An opinion piece in Education in Chemistry by Kristy Turner recently highlighted the potential bias that may lead to scholars being more likely to access, read and cite research from some parts of the world than others. This was actually an issue I was very aware of when a journal editor, as an international journal should aim to reflect research globally, but needs to apply common quality criteria.

This means that those working in contexts where there are no traditions of educational research, and limited resources to develop capacity, are at a disadvantage. I could think of one country where the journal received regular contributions, but which were almost always rejected (perhaps, always rejected?), as they simply did not amount to substantive accounts of research. These included well-intentioned, if sometimes quite convoluted, suggestions for mnemonic schemes to teach abstract conceptual subject matter, which offered absolutely no evidence that the proposed approach had ever been evaluated (if, indeed, ever applied). I was aware that any simple calculation of success rates in the journal would show that submissions from this particular national context had no chance of publication, and that few indeed ever got as far as referees 1. This might look like prejudice, even if it reflected application of the same quality criteria to all submissions. 2

On the other hand, the situation is slowly shifting. An excellent example is Turkey, which transformed from being a virtual non-participant in science education research publication to one of the most productive national sources of research published in the top journals, in just a couple of decades. I am aware of several other countries that are, if more slowly, supporting similar development in science education. So, the situation is complex: but Turner is absolutely right that we need to also be aware of a possible mind-set that assumes useful, quality research in science education will only be going on in a limited number of national contexts.

Being classified by the colour of my skin

But what really made me reflect on the piece was was not this important point, but that I was name-checked at the start of the article, along with a number of other educational research scholars, before Turner asked:

"What do these names have in common?

To start with they are all men and all White. More significantly, they all worked in the West (although some had collaborations further afield). This means that much of the education research we consume is produced from a Western perspective."

Turner, 2023

I am not sure I have ever seen myself called out in this public way as being "White", and I was not sure I was comfortable with being labelled in this way. For me, this was a mild discomfort – the kind that usefully leads one to reflect. By contrast, many people in this world experience being referred to by colour labels every day of their lives.

I readily identify as English, British and European, as simply a matter of fact: so, I suppose, 'Western' – guilty as charged. I have no qualms about being publicly labelled as a man. (Though I had no problem with being called 'Miss' by new secondary school students just moving up from primary schools where their class teacher had been 'Miss'. The pupils tended to be more embarrassed than me on these occasions – as was the tutee who once inadvertently called me 'Dad'. Yes, Tamsin, I still remember that.)

When I went to school, the world (at least as it was usually talked about) seemed simple in that regard. Humans came in two types – males and females. In my class in school there were boys and girls, and there was absolutely no ambiguity about this, and the difference was clearly marked: the boys wore shorts, the girls skirts or dresses. When I got to secondary school I studied metalwork and woodwork and technical drawing, whilst the girls studied their own subjects such as cookery. (Yes, I am that old.) Science dichotomised people into these classes of males and females (this was strictly known to be a simplification, but I do not recall any mention of other possibilities when I was a child), and there was a widely assumed perfect correlation with gender.

Of course, we now know this is utterly simplistic, and if such a regimented approach is imposed on people it is a burden that does not reflect the range of ways that people themselves experience their lives. It is now very common for people to attach their preferred pronouns to their web-pages and emails footers, and we appreciate that people have a right to self-identify in gender terms, and should not be assigned such an identify from the outside.

Original image by Krzysztof Niewolny from Pixabay

Should what is good for the goose also be good for the gander?

So, if we respect people's right to claim their own gender identity, what gives us the right to assign them to 'colour' categories? These categories were historically linked to what many scientists considered distinct varieties of human being – the different 'races'. That is, just as scientists might have recognised different varieties of a species, say different breeds of sheep, so there was considered to be a substantive and biologically justifiable basis for classifying people as members of different 'races'.

Those classifications were also not just seen as categorical, but often as ordinal – there were not only considered to be different races, but some of them were widely thought of (*) as more advanced, more civilised, perhaps even more evolved, than others; and it sometimes followed to many people that members of some races were of more inherent worth than others. (* At least, this was a common stance among people who self-identified as White!)

As is well known, this attitude led to many terrible events, and such bizarre notions as long-inhabited lands being 'discovered' by newcomers who therefore felt entitled to take possession of them: perhaps because they did not consider the inhabitants worthy of land and resource ownership; or perhaps because often the indigenous population took an attitude to the land and biota that it was not open to their ownership, but rather was sacred and deserving of being seen as in a form of relationship, rather than just being a source for exploitation. (That is, in many senses, the supposed 'more primitive' people had a more sophisticated and ecologically viable Worldview than those making the comparisons and seeing themselves as 'more civilised'.) That was one historical form of the 'Western perspective' that Tuner rightly warns about. 3

Science progresses: but not everyone keeps up

Science has moved on. We now know that, from a scientific perspective, there is only one human race. We all descend from early human ancestors that lived in Africa – so, for example, all of us in Britain are, if not ourselves migrants, ultimately the descendants of African migrants.

There are no strong categorical differences that allow us to form clear-cut classes of people (such as we can nearly dichotomise sex, even if we now realise that does not correlate to gender in a simple, direct way). Certainly, there are differences in populations that have long lived in different parts of the world: some groups are more likely to be lactose intolerant; more likely to suffer from, or be resistant to, specific diseases, and so forth. But these are statistical differences, not absolute ones.

An analogy for categorising people into 'races' based on physical characteristics (original image by Mote Oo Education from Pixabay)

To divide people into racial groups on that kind of basis makes as much sense as dichotomising adult people into males and females purely on height (i.e., the tallest 50% are male, by definition) simply because there is a statistical correlation between biological sex and adult height. Throughout human history, there has been social and genetic interchange between populations, and that is now more so than ever. We all have a mix of genes from a diverse range of ancestors – indeed most of us have few percent of genes that are considered Neanderthal. 4 So being 'White' is not simply a matter of genetics: any notion of a pure European genome is simply fantasy, akin to the deluded Nazi fantasies of Aryan blood lines. 5

Race is not a biological classification. Race is a social system of categorising people, not a scientific system. There are different races in the world only in a similar sense to how there are different styles of art or architecture in the world, or different modes of fashion (or styles of music, or genres of literature): because people have constructed such a system and imbued certain perceived differences with significance. But, there are not races in the world 'naturally' in the sense that there are different elements or different minerals out there for scientists to find. 6

The idea of several distinct human races can be seen as a historical scientific concept that was once given serious credence (just like phlogiston, or the luminiferous æther), but today should be seen as an alternative conception – a bit of folk-science that is actually a misconception.

Read about historical scientific conceptions

So, if I am seen as White, this is because I have certain physical characteristics that others perceive as being 'White' (i.e., physiognomy). Presumably skin colour is a primary factor, although I certainly do not have white skin (I have never seen anyone who actually looks white or black, and suspect this choice of labels is in part a reflection of the historical associations of these colours 7). I am basically a pink colour, although at certain times of year I go somewhat orange. I am not being flippant here – I am obviously of pale skin tone as would be associated with someone of European descent. But, again, we know that skin tone does not simply divide into a few clear categories: there is a whole spectrum out there, and most of us do not have entirely even pigmentation over all parts of the body, and/or are subject to some variation depending on environmental factors (and in England the average potential exposure to the Sun's rays in June is VERY different to in December!)

Now, I am not suggesting there might not be times when pointing out the colour of someone's skin might be useful – it might be very relevant in giving a description of a missing child or a mugger. But, Turner was not calling me White to help you recognise me, but to label me as someone associated with a 'Western' perspective. This of course is not a perfect correlation either. (I suspect that Rishi Sunak and Barack Obama would be widely considered to have Western perspectives).

'I hate the White man'

The musician Roy Harper wrote a song called 'I hate the white man' which appeared on his 1970 album 'Flat Baroque and Berserk'. He sings it live with real venom. When I first heard this song, it seemed strange to me, as here was a white man [sic, my label] singing how he hated the White man. It was heartfelt, but it seemed ironic. It did not occur to me that I was just assuming Roy was White because he looked white to me. (He is 'obviously' white, just as I, apparently, obviously am – that is, his skin tone is pinkish.) I never entertained another possibility: the notion that he should have the right not to identify with the people who's crimes he was singing about; that is, not to identify as a White man.

Roy Harper. He hates the white man.

(Image from Wikipedia, license: CC BY-SA 3.0)

So, should I be able to opt out of being put in an unscientific, racial category? Can I decline being White, and simply be a global citizen, a member of the human race, and so deserving the same level of respect and the same human rights as any other?

A dilemma

Of course it is not that easy. It is all very well someone like me refusing to self-identify with a racial label: there is still much discrimination and even targeted violence in many part of the world against people on racial grounds, and that would not be stopped by any personal self-identification of the victims. It is the perceptions of the abusers that matter in such situations, not how those on the receiving end see themselves. The Nazi's decided for themselves who was Jewish and so who deserved to be, say, removed from academic posts, or even incarcerated and exterminated, without regard to, for example, the victim's professed religion or record of Christian Church attendance.

Moreover, even if there are no strong genetic grounds to classify humans into a small number of 'races', the science of epigenetics is starting to reveal the cross-generational effects of extreme life-experiences (Meloni, 2019) such as slavery. The descendants of oppressed and impoverished people will continue to suffer relative to others for several generations. There may be no moral basis for asking children to pay for the 'sins of the fathers', but children of heavily sinned-against parents will still be at a disadvantage in life. That is not all about 'race': it might be about class, or the effects of war, but often racial identity (something with real effects, even if no scientific justification) can certainly be a factor.

If we do not identify with ethnic groups, then this makes monitoring of bias and discrimination difficult. How does an organisation know it is being equitable in relation to ethnic diversity, if no one chooses to self-identify with the traditionally majority, and/or privileged, groupings?

I think there is a genuine conundrum here. I look forward to the day when no rational person would see physiognomy as a useful basis for unscientifically classifying human beings, and, even if I am unlikely to live that long, hope we continue to move in that direction. But I understand why minority and oppressed groups find solidarity in such identification, and I appreciate the need for monitoring progress towards a fairer and more equitable society. So, Kristy, I fully understand why you call me 'White', even if I feel a little uneasy being labelled in that way.

Work cited:
  • Meloni, M. (2019). Impressionable Biologies: From the archaeology of plasticity to the sociology of epigenetics. Routledge.
  • Szöllösi-Janze, M. (2001). National Socialism and the sciences: reflections, conclusions and historical perspectives. In M. Szöllösi-Janze (Ed.), Science in the Third Reich (pp. 1-34). Berg.
  • Turner, K. (2023). Taking a global view. Education in Chemistry, 60, p.40
Notes:

1 Submissions to a research journal normally undergo editorial screening, so that (unpaid, expert) referees are not asked to spend time evaluating material in peer review that is out of scope for the journal or clearly inadequate (e.g., an empirical study lacking a methodology section).

Read about submitting to a research journal

2 I did highlight this issue at the journals' editorial board. The journal itself could do little about solving the problem, but the wider community might find ways to support development of research capacity in contexts where science educators aspire to be publishing work in international research journals.

3 Without in any sense wishing to undermine the terrible consequences that followed from widely held perceptions of racial differences, this can be seen as part of the wider commonplace phenomenon of categorising humans into various groupings in ways that are then used to justify treating some people as less worthy of respect and rights as others – for example the torture and judicial murder of Catholics/Protestants by Protestants/Catholics in parts of Europe when, sometimes, different members of the same nuclear family were classified into different groups.

4 It is sometimes said that on average a person has about 2% of Neanderthal DNA. Given that all the biota on earth is considered to ultimately have a common descent it is of course not surprising that human beings share some genes with, say, chimpanzees, and for that matter, bananas. However, it is not considered humans have chimpanzee ancestors (or banana ancestors, of course) but rather the two species evolved from a common ancestor population.

The particular interest in Neanderthal genes (and genes from Denisovans) is that it is considered that extant human populations carry genes acquired from Neanderthals when the two different populations co-existed, not from some precursor species they both evolved from. Whilst this is still an area of active research, the findings are widely interpreted to suggests that humans sometimes interbred with Neanderthals.

5 The Nazis thought that the German Volk descended from a distinct, discrete race, the Aryans – and set up scientific research projects to explore and develop the idea. Some of the ideas involved seem incredible:

"…Himmler rejected the Darwinist theory of evolution for the Aryans, presenting instead phantasies, according to which their earthy existence was derived from living shoots conserved in the ice of outer space…"

Szöllösi-Janze, 2001

6 Failure to appreciate this leads to confused questions such as whether discrimination against Jews should be considered racism. From a scientific perspective there are no races, so ipso facto the Jews are not a race. However, this is besides the point: if Jewish people are discriminated against, abused, attacked etc., either because of their religion, or because they are perceived as being members of an identifiable social ('ethnic') group, then this is clearly wrong and to be condemned, regardless of the label used.

If a legal system puts a particular weight on criminal offences that are motivated by racism (so, for example, punishments for those convicted have a premium), then what counts as a race for those purposes needs to be defined within that (social, i.e., legal) system, as natural science can have no role in determining social groupings that have no scientific basis.

7 This was lampooned in 'Star Trek: Enterprise', where Andorian Thy'lek Shran adopts the nickname 'pink skin' for Enterprise's Captain Archer.

From the Paramount Network Television series Star Trek: Enterprise

Are physics teachers unaware of the applications of physics to other sciences?

Confounding conceptual integration

Keith S. Taber

Tuysuz and colleagues seem to have found chemistry and physics teachers have a different attitude to the importance of integrating concepts from across the subjects.

Conceptual integration?

Conceptual integration is very important in science. That is, science doesn't consist of a large set of unrelated facts, but rather the ability to subsume a great many phenomena under a limited number of ideas is valued. James Clerk Maxwell is widely remembered for showing that electricity, magnetism and radiation such as light (that is, what we now call electromagnetic radiation) were intimately related, and today theoretical physicists seek a 'Grand Unified Theory' that would account of all the forces in nature. Equally, the apparent incompatibility of the two major scientific ideas of the early twentieth century – general relativity and quantum mechanics – is widely recognised as suggesting a fundamental problem in our current best understanding of the world.

So, conceptual integration can be seen as a scientific value: something scientists expect to find in nature 1 and something they seek through their research.

Learners may not appreciate this. When I was teaching physics and chemistry I was quite surprised to see how little some students who studied both subjects would notice, or indeed expect, ideas taught in one course to link to those in another (e.g., Taber, 1998).

A demarcation criterion?

I have even, only partially tongue-in-cheek, suggested that a criterion for identifying an authentic science education would be that it emphasises the connections within science, both within and across disciplines (Taber, 2006). 2

Sadly, there has been limited attention to this theme within science education, and very little research. I was therefore pleased to find a references to a Turkish study on the topic. 3

A study with teachers-in-preparation

Tuysuz, Bektas, Geban, Ozturk and Yalvac (2016) undertook an interview study with students preparing for school science teaching. One of their findings was:

"Generally speaking, while the pre-service chemistry teachers think that physics concepts should be used in the chemistry lessons, the pre-service physics teachers believe that these two subjects' concepts generally are not related to each other."

Tuysuz, Bektas, Geban, Ozturk & Yalvac, 2016

Reading this in isolation might seem to suggest that those preparing for chemistry teaching (and therefore, likely, chemistry teachers) saw more value in emphasising conceptual integration in teaching than those preparing for physics teaching (and therefore, likely, physics teachers).

Why might physics teachers give less value to conceptual integration?

It is easy to try to think of possible reasons for this:

  • Conjecture 1: chemistry teachers are aware of how chemistry draws upon physical concepts, and so are more minded to emphasise links between the subjects than physics teachers. 4
  • Conjecture 2: physicists, and so physics teachers, are more arrogant about their discipline than other scientists (cf. "All science is either physics or stamp collecting" – as Ernest Rutherford supposedly claimed!)
  • Conjecture 3: chemists are more likely to have also studied other science disciplines at a high level (and so are well placed to appreciate conceptual integration across sciences), whereas physics specialists are more likely to have mainly focussed on mathematics as a subsidiary subject rather than other sciences.

I imagine other possibilities will have occurred to readers, but before spending too much time on explaining Tuysuz and colleagues' findings, it is worth considering how they came to this conclusion.

Not an experiment

Tuysuz and colleagues do not claim to have undertaken an experimental study, but rather claim their work is phenomenology. It did not use a large, randomly selected (and, so, likely to be representative) sample of populations of pre-service science teachers (as would be needed for an experiment), but rather used a convenience sample of six students who were accessible and willing to help: three pre-service physics teachers and three pre-service chemistry teachers.

Read about sampling populations in research

It is not unusual for educational studies to be based on very small samples, as this allows for in-depth work. If you want to know what a person really thinks about a topic, you need to establish rapport and trust with them, and encourage them to talk in some detail – not just offer a rating to some item on a questionnaire. Small samples are perfectly proper in such studies.

What is questionable, is whether it is really meaningful to tease out differences between two identified groups (e.g., pre-service chemistry teachers; pre-service physics teachers) based on such samples. We cannot generalise without representative samples, so, when Tuysuz, Bektas, Geban, Ozturk and Yalvac write "Generally speaking…", their study does not really support such generalisation. The authors are only reporting what they found in their particular sample, and so the reader needs to contextualise their claim in terms of further details of the study, i.e., the reader needs to read the claim as

"Generally speaking, while the three pre-service chemistry teachers who volunteered to talk to us from this one teacher preparation programme think that physics concepts should be used in the chemistry lessons, the three pre- service physics teachers who volunteered to talk to us from this one programme believe that these two subjects' concepts generally are not related to each other."

Put in those terms, this is a very localised and limited kind of 'generally'.

This does not undermine the potential value of the study. That any future school science teachers might think that "these two subjects' concepts generally are not related to each other" is a worrying finding.

A confounded design

Another reason why it is important not to read Tuysuz's study as suggesting a general difference between teacher candidates in physics and chemistry, is because of a major confound in the study design. If the research had been intended as an experiment, where the investigators have to control variables so that there is only one differences between the different conditions, this would have been a critical flaw in the design.

The pre-service physics teachers and the pre-service chemistry teachers were taking parallel, but distinct, courses during the study. The authors report that the teaching approaches were different in the two subject areas. In particular, the paper reports that in the case of the pre-service chemistry teachers conceptual integration was explicitly discussed. The chemists – but not the physicists – were taught that conceptual integration was important. When interviewed, the chemists (who had been taught about conceptual integration) suggested conceptual integration was more important than the physicists (who had not been taught about conceptual integration) did!

  • This might have been because of their different subject specialisms;
  • It might have been because of the differences in the practice teaching courses taken by the two groups, such as perhaps the specific engagement of the chemists (but not the physicists) with ideas about conceptual integration during their course;
  • It might have been due to an interaction between these two factors (that is, perhaps neither difference by itself would have led to this finding);
  • And it might have simply reflected the ideas and past experiences of the particular three students in the chemists group, and the particular three students in the physicists group.

Tuysuz and colleagues found that, 'generally speaking', three students (who were chemistry specialists and had been taught about conceptual integration) had a different attitude to the importance of conceptual integration in teaching science to three other students (who were physics specialists and had not been taught about conceptual integration)

Read about confounding variables in research

The researchers might have just as readily reported that:

"Generally speaking, while the pre-service science teachers who had discussed conceptual integration in their course think that physics concepts should be used in the chemistry lessons, the pre-service science teachers who had not been taught about this believe that these two subjects' concepts generally are not related to each other."

Of course, such a conclusion would be equally misleading as both factors (subject specialism and presence/absence of explicit teaching input) vary simultaneously between the two groups of students, so it is inappropriate to suggest a general difference due to either factor in isolation.

Work cited:
Notes

1 Although science is meant to be based on objective observations of the natural world, scientists approach their work with certain fundamental assumptions about nature. These might include beliefs that

  • an objective account of nature is in principle possible (that different observers can observe the same things), and
  • that there is at some level a consistent nature to the universe (there are fixed laws which continue to apply over time)

assumptions that are needed for science to be meaningful. As these things are assumed prior to undertaking any scientific observations they can be considered metaphysical commitments (Taber, 2013).

[Download 'Conceptual frameworks, metaphysical commitments and worldviews']

Another metaphysical commitment generally shared by scientists as a common worldview is that the complex and diverse phenomena we experience can be explained by a limited number of underlying principles and laws. From this perspective, progress in science leads to increased integration between topics.

2 The term 'demarcation criterion' is often used in relation to deciding what should be considered a science (e.g., usually, astronomy is considered a science, and so is biochemistry; but not astrology or psychoanalysis). A famous example of a demarcation criterion, due to Karl Popper, is that a scientific conjecture is one which is in principle capable of being refuted.

Astronomers can use their theories and data to predict the date of the next solar eclipse, for example. If the eclipse did not occur when predicted, that would be considered a falsification.

By contrast, if a psychotherapist suggested a person had personality issues due to repressed, unresolved, feelings about their parents, then this cannot be refuted. (The client may claim having positive and untroubled relationships with the parents, but the therapist does not consider this a refutation as the feelings have been repressed, so they are not consciously available to the client. The problem can only be detected indirectly by signs which the therapist knows how to interpret.).

3 I became aware of the study discussed here when reading the work in progress of Louise Vong, who has been doing some research in this important topic.

4 Physics concepts are widely applied in chemistry, but not vice versa. So, this is suggesting that chemistry teachers have more need to refer to physics in teaching their subject than the converse.

However, we could also have looked to explain the opposite finding (had it been reported that pre-service physics teachers paid more attention to conceptual integration than pre-service chemistry teachers) by suggesting physics teachers have more reason to refer to chemistry topics when discussing examples of applications of concepts being taught, than chemistry teachers have to refer to physics topics.

Burning is when you are burning something with fire …

Iconic chemical triangles

Keith S. Taber

Derek was a participant in the Understanding Science Project. When I interviewed Derek soon after the start of his secondary schooling, he told me he liked science, and was currently studying 'burning'.

So, I asked him what that was:

What is burning?

[pause, c.2s]

When [pause, c.2s] a fuel, oxygen and heat gets – in, erm, I'm not quite sure how to explain, but it's like – you get the triangle of fire, and then, burning is just when you've got fire and you're burning something with it.

Okay, so you'd recognise it if you saw it, would you?

Yeah.

Yeah, but maybe it's not that easy to explain?

Yeah.

The notion that 'burning is just when you've got fire and you're burning something with it' – might be considered tautological:

  • burning is when you are burning something

Scientists look to explain natural phenomena with theories, principles, models, and so forth. But for most people, phenomena that they have been familiar with since very young (such as a dropped object falling) do not seem to need explanation – as they are seen as just natural events (Watts & Taber, 1996).

Derek knew about the fire triangle, but his response reminded me of another triangle that is often referred to by science educators.

Johnstone's triangle

For many years Prof. Alex Johnstone (1930-2017) worked at the Centre for Science Education that he founded at the University of Glasgow; where he undertook, supervised, and collaborated on, a good many projects in science education – especially, but not only, relating to the teaching and learning of chemistry and physics in higher education.

However, one of Johnstone's most influential publications must be the short article he published in the School Science Review (Johnstone, 1982) – the secondary science journal of the Association for Science Education. In this short piece he argued that in each of biology, chemistry, and physics, learning difficulties in part derived from how the subject was taught at several 'levels' at once, asking young learners to think simultaneously on different planes as it were. In each of these science subjects, this could be represented by a triangle. In many lessons students would be asked to think about, and inter-relate, considerations from the viewpoints of several vertices.

Johnston's chemistry triangle distinguished between three levels:

  • the macroscopic (the scale at which people observe and handle materials);
  • the submicroscopic (molecular) scale at which many chemical explanations are developed;
  • the symbolic level – where abstract symbols are used to represent the chemistry

"Those of us who are academic chemists can view our subject on at least three levels.

There is the level at which which we can see and handle materials, and describe their properties in terms of density, flammability, colour and so on. We are also interested in the possibility of conversion of one material into another with consequent changes in properties.

A second level is the representational one in which we try to represent chemical substances by formulae and their changes by equations. This is part of the sophisticated language of the subject.

The third level is atomic and molecular, a level at which we attempt to explain why chemical substances behave the way they do. We invoke atoms, molecules, ions, structures, isomers, polymers etc to give us a mental picture by which to direct our thinking and rationalize the descriptive level mentioned above.

These levels could be called (a) descriptive and functional, (b) representational, (c) explanatory. Trained chemists jump freely from level to level in a series of mental gymnastics. It is eventually very hard to separate these levels."

Johnstone, 1982 (added emphasis)

Over the years there have been many attempts to apply, elaborate, and refine Johnston's triangle, and it has been an idea that has proved very productive in thinking about learning difficulties in the subject.

"Chemistry seeks to provide qualitative and quantitative explanations for the observed behaviour of elements and their compounds. Doing so involves making use of three types of representation: the macro (the empirical properties of substances); the sub-micro (the natures of the entities giving rise to those properties); and the symbolic (the number of entities involved in any changes that take place). Although understanding this triplet relationship is a key aspect of chemical education, there is considerable evidence that students find great difficulty in achieving mastery of the ideas involved…" (Publisher's description)

One well-respected, edited, scholarly book ('Multiple Representations in Chemical Education' – Gilbert & Treagust, 2009) consisted of contributions exploring implications of the idea. Indeed, now, there is even a book entitled 'The Johnstone Triangle' (Reid, 2021) with the telling subtitle: 'the key to understanding chemistry'!

Johnstone's triangle is now the subject of a book

Reconceptualisation

Derek was just being introduced to burning as a science topic, and for him it was still just a familiar phenomenon rather than a theoretical construct. We have all seen fires, and can recognise when something is burning – but how many people really know what fire is?1 Burning and fire are everyday concepts – fire is an impressive phenomenon to a young child: one that is salient enough to be noticed. The child's brain then recognises different instances of fire as being similar and it abstracts a spontaneous concept – that there is a category of events in the world that appear like this.

Of course, the brain of the young child does this without using language (it forms a category of events in the sense that it readily recognises new instances – it does not yet have access to have technical notions of 'category', 'concept', 'abstraction' of course.) And the child does not instinctively know this is called 'fire' or 'el incendio' or 'l' incendie' or whatever, until someone who is a more mature member of the child's natural language community shares this label.2

School science will involve learning that there is a formal scientific concept3 called 'combustion' that is basically the chemist's name for burning. However, 'combustion' is a technical term, so combustion will be defined in terms of other concepts. So, whereas in everyday life we recognise what counts as a fire or burning using the brain's inherent pattern-recognition mechanism (a spontaneous conception), in chemistry we have a technical definition (a scientific concept defined in relation to to other scientific concepts, and so 'theoretical').

That is, in everyday life, if you told someone you saw something on fire, it is unlikely anyone (leaving aside science teachers) would ask you which criteria you used to know this: you did not deliberate on the matter, you simply saw, and instantly recognised, a fire. When you refer to a fire, the other person recognises what you mean because they have learnt 'fire' to be the label for their own spontaneously formed conception that allows their perceptual-cognitive system to instantly recognise a fire.

But, for a chemist, combustion is one class of chemical reaction (so the learner can only understand combustion in chemical terms if they have an appreciation of what a chemical reaction is), which only makes sense to someone who has reasonable idea what a scientist means by a substance, as chemical reactions are changes resulting in different substances. Here we have shifted from everyday notions to the theoretical descriptions of science.

In school chemistry, everyday phenomena (e.g., burning) are reconsolidated in terms of technical concepts and language (e.g., combustion). (From Taber, 2013)

The invisible nanoscopic world

But chemists are seldom satisfied with macroscopic accounts – even when posed in technical language. Rather, students will be taught to explain the observable macroscopic phenomena in terms of invisible entities which have unfamiliar properties. Imagined entities such as molecules4, nanoscopic systems which are best understood as fuzzy balls of fields – that have no actual surface, and are mostly tenuous 'clouds' of charge. (Molecules are sometimes modelled as if billiard balls, or sets of balls connected by sticks, but this is just an attempt to represent entities quite unlike the familiar referents available to learners in ways they can make sense of.)

That is, combustion will be explained as a rearrangement of electrons and atomic cores that changes one set of molecules (of the reactants in the reaction) into another (the products). This process will involve energy changes, due to differences in stability of different sets of molecules, and will progress through the breaking and making of chemical bonds.

If the learner is able to form a mental image of (i.e., imagine) chemical reactions at the nanoscopic level, and see how this can be used to explain an actual observable phenomenon (such as a fire), they then also have to learn how chemists often represent these ideas in what is in effect a specialist language – involving chemical formulae, and reaction equations, and the like.

So, when Derek was using a Bunsen burner to set fire to pasta and (not quite set fire to) raisins as he reported to me, he was using a chemical reaction that might be summarised by the chemist or science teacher as:

CH4 + 2O2 ➞ CO2 + 2H2O

Johnstone suggested that the symbolic representation was the third level, alongside the macroscopic and submicroscopic. He was absolutely right that it added to the 'learning demand'. However, there is another complication in that many of these key representations (the formulae and equations) are ambiguous as they can represent either the macroscopic level of substances weighed out in grammes (2O2 would represent 64 g of the substance oxygen, although as it is a gas it would normally be measured by volume) or the individual imagined entities of the molecular world (where 2O2 would mean two molecules of oxygen).

Useful ambiguity

This is useful ambiguity for the chemist – but an added complication for the learner who has to follow the teacher's transitions where one moment a symbol reflects a test tube of stuff, and the next some molecule. Because of its role in bridging between the two very different scales at which we explain chemistry I prefer to see these symbols as being along one side of the triangle (whilst separating out the everyday phenomenological level from the technical, theoretical descriptions used by science). However, whatever version of Johnstone's triangle is applied, it has become something of an iconic image in chemistry education.

The chemist's triplet: a variation on Johnstone's triangle (from Taber, 2013)

Another iconic triangle

Derek had not yet been introduced to all this, and he was still operating with burning as a phenomenon:

And why is this important, do you think? Why do you think we study burning?

[pause, c.2s]

I'm not sure.

No one's told you that?

No.

Is it fun, is it a fun topic?

Yeah.

What Derek did seem to have learned well was the fire triangle.

But you have this 'triangle of fire'. So does that mean that fire is always a triangular shape?

No.

So, what's a triangle of fire?

You need three things to make a fire, which is oxygen, heat and fuel.

Okay, so what if I had erm some fuel and some heat, but I didn't have any oxygen, but maybe I've got lots of fuel?

No – wouldn't have fire.

I can't have extra fuel instead?

No.

No?

You need the three things.

What if I've got lots and lots of fuel, and lots and lots of oxygen, but it's very, very cold?

No.

No, that won't work either. So I always have to have the three things?

Yeah.

Derek stuck to his claim – you always needed all three. This is a useful heuristic (useful if ever one is faced with a fire as it tells you can act by just removing one of the three essentials) even if (like most heuristics) it will sometimes fail, e.g.

  • some materials will continue burning in the absence of an external supply of oxygen as they have an internal source;
  • chlorine will support combustion in place of oxygen (but that's seldom a practical issue in everyday situations) ;
  • substances have an auto-ignition temperature (where they can spontaneously ignite), and for a few substances this is around or below room temperature;

These exceptions do not undermine the general utility of the' 'triangle'.

Some useful learning had gone on here – and potentially not just about fire, because the idea that one factor may be limiting on a process is a generally useful principle (e.g., plants grown in a soil depleted in potassium will not thrive, no matter how much sunlight, water, nitrate and phosphate is present).

But the fire triangle, even if it is not supported by a deep understanding of chemical principles, is worth teaching because of its practical value. It seems to offer a heuristic that people accept and recall. And rather like Johnston's triangle, it seems to have become rather iconic. At least, I assume that is why when COVID-19 infection rates were high, the fire triangle was used as a familiar analogy to persuade people to avoid the 'oxygen' of social mixing…

"I like to think of COVID as a fire, if we are the fuel, social mixing is the oxygen that allows the fuel to burn…'"

Read 'COVID is like a fire because…'

Work cited
Notes

1 It has been mooted that fire should be understood as an example the 'fourth' phase of matter, plasma – that is an ionised gas.5 But actually fire is more complicated than this as it contains a mixture of reactant and product molecules and the molecular fragments that form intermediate and/or transition states. Some chemical reactions, when studied at the molecular level, largely follow a single reaction path. But combustion tends to be much more complex with multiple pathways involving many different ions and molecular fragments.

Read: The states of (don't) matter? Which state of matter is fire?

So, fire is a multiphase mixture, more akin to a solution, aerosol, or suspension, than to a gas or plasma.

2 The child does not know this is called fire, and when she is told this she may not realise that such names are social conventions – according to Jean Piaget's research young children may assume that things in the world have (that is, have always had) a name that people have had to learn.

This childish idea reflects superstitious notions about names that are part of some magical systems of knowledge – 'the law of names': the idea that if you know a person or thing's real name this gives you over over them/it.

3 A very influential theory due to Lev Vygotsky takes the distinction between spontaneous concepts formed automatically, and formal taught concepts that are shared through social interaction (such as teaching). These latter kinds of concepts are usually translated from Vygotsky's Russian as 'scientific' though this is meant in the broad sense of any formal field of study. A key point emphasised by Vygotsky was that, assuming the learners could relate a taught concept to existing spontaneous concepts (that is, 'meaningful learning' occurred), they would actually come to operate with a concept which was a hybrid developed from the interaction of the intuitive understanding and the learned technically defined notion – a melded conception.

4 By referring to molecules and ions and electrons as imagined entities, I am not suggesting they are only imaginary. Most (if not all) scientists today see them as real things (even if strictly our evidence is indirect, and they arguably remain theoretical constructs). But a teacher cannot directly show the class a molecule or an electron, even if some types of imaging equipment do now produce representations of individual atoms. For the learners (and I would suggest even the teacher) these are only ever imagined entities. Yet, we expect students to do a good deal of thinking about, and with, these imagined entities.

5 If we are expanding the three states of matter, then there is an argument for making plasma the 5th phase:

  • Bose-Einstein condensates
  • solids
  • liquids
  • gases
  • plasma
  • (quark 'soups'?)

Would you like some rare earths with that?

A chemically illiterate internet meme

Keith S. Taber

The challenge of popular science writing

I often enjoy reading popular accounts of science topics, but sometimes one comes across statements that are vague or dubious or confusing – or simply wrong. Some of this reflects a basic challenge that authors of popular science share with science teachers and other science communicators: scientific ideas are often complex, subtle and abstract. Doing them justice requires detailed text and technical terminology. Understanding them often depends upon already having a good grasp of underpinning concepts. That is fine in a formal report for other scientists, but is not of any value to a non-specialist audience.

So, the author has to simplify, and perhaps round off some of the irregular detail; and to find ways to engage readers by using language and examples that will make sense to them. That is, finding ways to 'make the unfamiliar familiar'.

Read about making the unfamiliar familiar in teaching

I am sure that often the passages in popular science books that I as a scientist 1 get grumpy about are well motivated, and, whilst strictly inaccurate, reflect a compromise between getting the science perfect and making it accessible and engaging for the wider readership. Sometimes, however, one does get the impression that the author has not fully grasped the science they are writing about.

"Lucy Jane Santos is the Executive Secretary of the British Society for the History of Science…"

Public engagement with radium

I very much enjoyed reading a book, 'Half lives', by the historian of science Lucy Jane Santos, about how in the decades after its discovery by Pierre and Marie Curie, radium was the subject of wide public interest and engagement. One of the intriguing observations about this newly discovered element was that it appeared to glow in the dark. We now know that actually the glow comes from nitrogen in the air, as radium is radioactive and emissions by radium 'excite' (into a higher energy state) nitrogen molecules, which then emit visible light as they return ('relax') to their 'ground' state. This production of light without heating (a phenomenon generally called luminescence), when it is due to exposure to radioactivity, is known as radioluminescence.

Today, many people are very wary of radioactivity – with good reason of course – but Santos describes how at one time radium was used (or at least claimed as an ingredient) in all kinds of patent medicines and spa treatments and cosmetics (and even golf balls). This was a fascinating (and sometimes shocking) story.

What substance(s) can you find in quinine?

I did find a few things to quibble over – although across a whole book it was, only, a few. However, one statement that immediately stood out as dodgy science was the claim that quinine contained phospor:

"Quinine contains phosphor, a substance that luminesces when exposed to certain wavelengths of light…"

Santos, 2020

This may seem an unremarkable statement to a lay person, but to a scientist this is nonsensical. Quinine is a chemical compound (of carbon, hydrogen, nitrogen and oxygen), that is – a single substance. A single substance cannot contain another substance – any more than say, a single year can contain other years. An impure sample of a substance will contain other substances (it is in effect a mixture of substances), but quinine itself is, by definition, just quinine.

Molecular structure of the chemical compound quinine (C20H24N2O2) – a pure sample of quinine would contain only (a great many copies of) this molecule.

Note – no phosphorus, and no rare earth metal atoms.

(Image source: Wikimedia)

Confusing terminology

The term 'phosphor' refers to a luminescent material – one that will glow after it has been exposed to radiation (often this will be ultraviolet) or otherwise excited. The term is usually applied to solid materials, such as those used to produce an image in television and monitor screens.

The term derives by reference to the element phosphorus which is a luminescent substance that was accordingly itself given a name meaning 'light-bearing'. The term phosphorescent was used to describe substances that continue to glow for a time after irradiation with electromagnet radiation ceases. But it is now known that phosphorus itself is not phosphorescent, but rather its glow is due to chemiluminescence – there is a chemical reaction between the element and oxygen in the air which leads to light being emitted.

The widely used term phosphor, then, reflects an outdated, historical, description of a property of phosphorus; and does not mean that phosphors contain, or are compounds of, phosphorus. There is clearly some scope for confusion of terms here. 2

termmeaning
luminescencethe emission of light by a cold object (in contrast to incandescence)
– chemiluminescencea form of luminescence due to a chemical reaction
– – bioluminescencea form of chemiluminescence that occurs in living organisms
– electroluminescencea form of luminescence produced by passing electrical current through some materials
– photoluminescencea form of luminescence due to irradiation by electromagnetic radiation, such as ultraviolet
– – fluorescence a type of photoluminescence that only occurs whilst the object is being excited (e.g., by exposure to ultraviolet)
– – phosphorescencea type of photoluminescence that continues for some time after the object has been being excited (e.g., by exposure to ultraviolet)
– radioluminescencea form of luminescence due to a material being exposed to ionising radiation (e.g., 𝛂 radiation)
– sonoluminescencea form of luminescence due to a material being exposed to sound
phosphora material that exhibits luminescence
phosphorusa chemical element that exhibits chemiluminescence (when exposed to air)
There is a range of terms relating to luminescence. Here are some of those terms.

Some central ideas about luminescence (represented on a concept map)
A traditional medicine

Quinine, a substance extracted from the bark of several species of Cinchona, has long been used for medicinal purposes (e.g., by the Quechua people of the Americas 3), as it is a mild antipyretic and analgesic. It is an example of a class of compounds produced by plants known as an alkaloids. Plant alkaloids are bitter, and it is thought their presence deters animals from eating the plant. We might say that Quechua pain medication is a bitter pill to swallow.

Modern science has often adopted and developed technologies that had long been part of the 'traditional ecological knowledge' of indigenous groups – such as making extracts from Cinchona bark to use as medicines.

Sadly, the original discovers and owners of such technologies have not always been properly recognised when such technologies have been acquired, transferred elsewhere, and reported. 3

(Image by GOKALP ISCAN from Pixabay)

Quinine is an ingredient of tonic water (and bitter lemon drink) added because of its bitter taste.

(Why deliberately make a drink bitter? Quinine has anti-malarial properties which made it a useful substance to add to drinks in parts of the world where malaria is endemic. People liked the effect!)

Quinine glows when exposed to ultraviolet light. It is luminescent. To be more specific, quinine is photoluminescent. (This is responsible for the notion that someone offered a gin and tonic at a disco should test it under the 'blacklights' to make sure they have not been given pure gin to drink. Although, I am slightly sceptical about whether the kind of people that drink 'G&T's go to the kind of dances that have ultraviolet lighting.)

"I do apologise, I think I might have just splashed a tiny droplet of my tonic water on you"

(Image by Victoria_Watercolor from Pixabay)

It is reasonable to describe quinine as a phosphor in the wider sense of the term – but it does not contain another phosphor substance, any more than, say, iron contains a metallic substance or sulphur contains a yellow substance or sucrose contains a sweet substance or copper a conducting substance. So, a more accurate formulation would have been

"Quinine [is a] phosphor, a substance that luminesces when exposed to certain wavelengths of light…"

or, perhaps better still, simply

"Quinine [is] a substance that luminesces when exposed to certain wavelengths of light…"

Ask the oracle

I was intrigued at why Lucy Jane Santos might have been confused about this, until I did a quick internet search. Then I found a range of sites that claimed that quinine contains phosphors – indeed, often, rare earths are specified.

The rare earths (another unfortunate historic choice of name, as it transpired that they are neither especially rare nor 'earths', i.e., oxides) are a group of metallic elements. They are not as well known as, say, iron, copper, zinc, aluminium or gold, but they have with a wide range of useful applications.

Scandium, the first of the 'rare earth' metals. Probably not what you want in your tonic water.

(Creative Commons Attribution 3.0 Unported License, sourced from https://images-of-elements.com/scandium.php)

If something is repeated enough, does it become true?

Clearly there are not rare earths in quinine. So, the following quotes (from sites accessed on 7th March 2023) proffer misinformation.

"If you want to get a bit more scientific about it…. quinine contains rare earth compounds called phosphors.  These are the substances which glow when they are hit with particular wavelengths of the EM spectrum, including UV light.  Phosphors absorb UV light and then emit it in their own colour, in this case glowing blue light."

https://www.iceandaslice.co.uk/blogs/news/why-does-your-gin-and-tonic-glow-blue-in-ultraviolet-light

This claim is odd, as the previous paragraph explained more canonically: "why does quinine absorb UV light (the invisible component of sunlight that produces sun tans and sunburns!)? It is due to the structure of the quinine molecule, which enables it to take in energy in the form of invisible UV light and immediately radiate some of that same energy in the form of visible blue light." Other compounds cannot be inside a molecule – so this more canonical explanation is not consistent with quinine containing other "substances" which were "rare earth compounds."

"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light."

https://sciencing.com/quinine-fluorescent-5344077.html

The following extract appeared under the subheading "Why is quinine fluorescence?" That reflects a category error as quinine is a substance and fluorescence is a process (and fluorescent the property) – so, presumably this should have read why is quinine fluorescent?

Why Quinine Glows

Quinine contains rare earth compounds called phosphors. … Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light.

https://allfamousbirthday.com/faqs/does-tonic-water-make-things-glow-in-the-dark/

"Want to know one more fun fact about quinine? It glows.
Rare Earth compounds called phosphors in quinine glow under certain circumstances."

https://www.mixlycocktailco.com/blogs/news/does-tonic-water-go-bad

Why Does Tonic Water Glow Under UV Rays?

Tonic water glows and [sic] will fluoresce under UV rays because of quinine in it. Quinine is one of the most important alkaloids found in the cinchona bark, among many others. It has some rare earth compounds known as phosphors that glow when they hit certain wavelengths of the UV light. Phosphors in the quinine absorb the UV light and then reflect it or emit it again in the form of glowing blue light.

https://www.sawanonlinebookstore.com/why-does-tonic-water-glow-under-uv-rays/

Making magic mud – or not

Perhaps the most bizarre example was a site, 'emaze' which offered to show me "How to create magic mud…in 17 easy steps"

Step 1 was

"wash your potatoes!!!!"

However, perhaps due to exclamation fatigue(!), this went in a different, if now familiar, direction with step 2:

"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light"

https://app.emaze.com/@AORQCIII#/16

This text was then repeated as each of steps 3-14. (Sadly steps 15-17 seemed to have been missed or lost. Or, perhaps not so sadly if they were just further repeats.) The first screen suggests this presentation was "done by Dr. Meena & Maha" but if Dr. Meena & Maha really exist (if you do, I am sorry, the internet makes me very sceptical) and 'done this', it is not clear if they got bored with their task very quickly, or whether the server managed to corrupt a much more coherent presentation when it was uploaded to the site.

This 'emaze' presentation seems to want to emphasise how quinine contains rare earth compounds…

According to Google, the site 'Course Hero' suggested

"Phosphors, which are found in quinine, are rare earth compounds. These chemicals glow when they are struck with particular wavelengths of the EM spectrum, …"

https://www.coursehero.com › Chemistry › 44733249–I…

but unfortunately (or perhaps fortunately given that snippet), the rest of the text seemed to be behind a pay-wall. This did not offer a strong incitement to pay for material on the site.

Toys coated with phosphorus?

Another website I came across was for a shop which claimed to be selling glow-in-the-dark objects that were made with phosoporus that needed to be illuminated to initiate a glow: a claim which seems not only scientifically incorrect (as mentioned above, phosphorus is not photoluminescent – it glows when in contact with air as it oxidises), and so unlikely; but, otherwise, dangerous and, surely, illegal.

Read about unscientific luminous creations

Defining scientific terms – badly

During my search, I came across a website (grammarist.com) offering to explain the difference between the words phosphorous and phosphorus. It did not discuss rare earths, but informed readers that

"Phosphate: Noun that means an electrically charged particle.
Phosphorus: Also a noun that means a mineral found in phosphate."
…We've already established that phosphorus is the simple mineral found in the particle phosphate, but phosphor is something else altogether."

https://grammarist.com/spelling/phosphorous-phosphorus/

So, that's 'no', 'no', 'no', and…I think at least one more 'no'.

Phosphorus is a reactive element, and is not found in nature as a mineral. To a scientist, a mineral is a material found in nature – as a component of rocks. Unfortunately, in discussing diet, the term minerals is often associated with elements, such as, for example, phosphorus, iodine, potassium and iron that are necessary for good health. However, one would not eat the element iron, but rather some compound of it. (Foods naturally contain iron compounds). And trying to eat phosphorus, iodine or potassium (rather than compounds of them) would be very hazardous.

So, whilst a nutritional supplement might well contain some minerals in the composition, strictly they are there as compounds that will provide a source of biologically important elements, and they will be metabolised into other compounds of those elements. (Iron from iron compounds will, for example, be used in synthesising the haem incorporated into red blood cells.) Unfortunately, learners commonly have alternative conceptions ('misconceptions') about the difference between mixtures and compounds and assume a compound maintains the properties of its 'constituent' elements (Taber, 1996).

"Compound is one or more elements mixed together"

alternative conception elicited from an Advance level chemisty student

The grammarist.com entry helpfully warned us that phosphate was "not to be confused with phosphoric acid, a chemical compound found in detergents and fertilizers". I suspect it is only found in detergents and fertilisers when something has gone wrong with the production process (notwithstanding diluted phosphoric acid has been used directly as a fertiliser) 4. It is a corrosive and irritant substance that can cause bronchitis – although tiny amounts are added to some colas. [n.b., cocaine also once featured in some cola, but that is no longer allowed.]

  • An ion is an electrically charged particle
  • The phosphate ion is one example of a type of ion.
  • Phosphates (such as calcium phosphate) are substances that contain phosphate ions.

So, phosphates contain electrically charged particles (phosphate ions), but that does not make phosphate an electrically charged particle, just as

  • blue does not mean a large marine mammal
  • bank does not mean a day of celebration where people do not need to go to work
  • vice does not mean a senior executive officer
  • motor does not mean a two wheeled vehicle
  • compact does not mean a flat circular object
  • final does not mean a simple musical instrument played with the breath
  • free does not mean a meal taken around noon or soon after, and
  • meal does not mean a token that provides entry or service

Grammarist invited feedback: I sent it some, so hopefully by the time you read this, the entry will have been changed.

It was on the internet: it must be true

The internet is an immense and powerful tool giving access to the vast resources of the World Wide Web. Unfortunately, the downside of a shared, democratic, free to access, reservoir of human knowledge is that there is no quality control. There is a lot of really good material on the web: but there is also a lot of nonsense on the web.

One example I have referred to before is the statement:

"energy is conserved in chemical reactions so can therefore be neither created nor destroyed"

This has the form of a logical structure

X so therefore Y

which is equivalent to

Y because X:

"energy can be neither created nor destroyed because it is conserved in chemical reactions"

This is just nonsense. There is no logical reason why the conservation of energy in chemical reactions implies a general principle of energy conservation.

We can deduce the specific from the general (days have 24 hours, so Sunday has 24 hours) but not the general from the specific (January has 31 days, so months have 31 days).

Perhaps this is easily missed by people who already know that energy is always conserved.

A parallel structure might be:

"association football teams always consist of eleven players so therefore sports teams always consist of eleven players"

"sports teams always consist of eleven players because association football teams always consist of eleven players"

This is 'obviously' wrong because we know that rugby teams and netball teams and volleyball teams and water polo teams (for example) do not consist of eleven players.

Yet, if you search for "energy can be neither created nor destroyed because it is conserved in chemical reactions", you will find that this claim is included on the public websites of many schools (Taber, 2020). That is because, despite being wrong, it has authority – it is included in the English National Curriculum for Science (which I find shocking – we all make mistakes, but did nobody check the document before publication?) The English government department responsible was made aware of the error but does not think that it is a priority to make corrections to the curriculum.

Artificial (ignorant) intelligence

But what about quinine containing rare earth compounds? A notion that is structurally similar to claiming that

  • France contains South American countries, or
  • 'Great Expectations' contains Jane Austin novels, or
  • February contains Autumn months, or
  • Cauliflower contains citrus fruits, or
  • Beethoven's 5th Symphony contains Haydn concerti

(in other words, something obviously silly to someone who has a basic understanding of the domain – chemistry or geography or literature or the calender or botany/horticulture or music – because it suggest one basic unit contains other units of similar status).

How does this error appear so often? Quite likely, a lot of website now are populated with material collected and collated by machines from other websites. If so, it only takes one human being (or government department) to publish something incorrect, and in time it is likely to start appearing in various places on the web.

There is currently a lot of talk of how artificial intelligence (AI) is getting better at writing essays, and answering questions, and even drafting lectures for busy academics. AI seemingly has great potential where it is provided with high quality feedback. Perhaps, but where the AI is based on finding patterns in publicly available texts, and has no real ability to check sense, then I wonder if the www is only going to become more and more polluted with misinformation and nonsense.

I do not know where Lucy Jane Santos got the idea that there are other substances in the single substance quinine (akin to having other countries in France), but if she did a web-search and relied on what she read, then I am in no position to be critical. I use the web to find things out and check things all the time. I am likely to spot gross errors in fields where I already have a strong background…but outside of that? I do seek to evaluate the likely authority of sources – but that does not mean I could not be taken in by a site which looked professional and authoritative.

The web started with imperfect people (because we all are) posting all kinds of material – with all kinds of motivations. I expect most of it was well-meaning, and usually represented something the poster actually believed; and indeed much of it was valid. However, a 'bot' can search, copy, and paste far quicker than a person, and if the internet is increasingly authored by programs that are indiscriminately copying bits and pieces from elsewhere to collage new copy to attract readers to advertising, then one cannot help wonder if the proportion of web-pages that cannot be trusted will be incrementally coming to dominate the whole network.

I (a fallible, but natural intelligence) hope not, but I am not very optimistic.

Work cited:

Notes:

1 Although my own research has been in science education and not one of the natural sciences, I am pleased that the learned societies (e.g. the Institute of Physics, the Royal Society of Chemistry, etc.) and the UK's Science Council, recognise the work of science educators as professional contributions to science.

2 One internet site suggests:

Luminescence is caused by various things like electric current, chemical reactions, nuclear radiation, electromagnetic radiation, etc. But phosphorescence takes place after a sample is irradiated with light.

• Phosphorescence remains for sometime even after the lighting source is removed. But luminescence is not so.

https://www.differencebetween.com/difference-between-luminescence-and-vs-phosphorescence/

The second paragraph is nonsensical since phosphorescence is a type of luminescence. (It should be, "…fluorescence" that does not.) The first paragraph seems reasonable except that the 'but' seems misplaced. However 'in the light of' the second sentence (which sees phosphorescence and luminescence as contrary) it seems that the (contrasting) 'but' was intended, and whoever wrote this did not realise that light is a form of electromagnetic radiation.

Another, more technical, site suggests,

Luminescence is the emission of light by a substance as a result of a chemical reaction (chemiluminescence) or an enzymatic reaction (bioluminescence).

https://www.moleculardevices.com/technology/luminescence

Here again a contrast is set up:

  • chemiluminescence (due to a chemical reaction) versus
  • bioluminescence (due to an enzymatic reaction).

However, the keen-eyed will have spotted that "an enzymatic reaction" is simply a chemical reaction catalysed by an enzyme. So, bioluminescence is a subtype of chemiluminescence, not something distinct.

3 Some sources claim that the medicinal properties of cinchona bark were discovered by Jesuit missionaries that travelled to South America as part of European imperial expansion there.

Nataly Allasi Canales of the Natural History Museum of Denmark, University of Copenhagen is reported as explaining that actually,

"Quinine was already known to the Quechua, the Cañari and the Chimú indigenous peoples that inhabited modern-day Peru, Bolivia and Ecuador before the arrival of the Spanish…They were the ones that introduced the bark to Spanish Jesuits."

https://www.bbc.com/travel/article/20200527-the-tree-that-changed-the-world-map

Learning about the history of indigenous technologies can be complicated because:

  • often they are transmitted by an oral and practice culture (rather than written accounts);
  • traditional practices may be disrupted (or even suppressed) by colonisation by external invaders; and
  • European colonisers, naturalists and other travellers, often did not think their indigenous informants 'counted', and rather considered (or at least treated) what they were shown as their own discoveries.

4 This again seems to reflect the common alternative conception that confuses mixtures and compounds (Taber, 1996): phosphoric acid is used in reactions to produce fertilizers and detergents, but having reacted is no longer present. It is a starting material, but not an ingredient of the final product.

Just as we do not eat iron and phosphorus, we do not use washing powders that contain phosphoric acid, even if they have been prepared with it. (Increasingly, phosphates are being replaced in detergents because of their polluting effects on surface water such as rivers and lakes.)

5 This gives the impression to me that the Department of Education sees schooling as little more than a game where students perform and are tested on learning whatever is presented to them, rather than being about learning what is worth knowing. There is surely no value in learning a logically flawed claim. Any student who understands the ideas will appreciate this statement is incorrect, but perhaps the English Government prefers testing for recall of rote learning rather than looking for critical engagement?

Unscientific luminous creations

Q: Which form of phosphorus both glows and is non toxic?

Keith S. Taber

I have just sent of an email to a company claiming to be selling glow-in-the-dark products containing non-toxic phosphorus…

The site offers answers to a range of questions, but unfortunately gets a lot wrong

Dear Pete's Luminous Creations

I am writing to raise concern about misleading information on your website, specifically some of the claims made on the page:

(accessed today, 18th March 2023).

This page contains a number of scientifically incorrect statements, but I am most concerned about your misleading characterisation of phosphorus as a 'safe' material.

Scientific errors

Your site claims that

  • "phosphorus…has the ability to absorb and store surrounding light"
  • "the ability to absorb and store surrounding light…works similar to the natural process of photosynthesis"
  • "Phosphorus glow absorbs and stores surrounding light. When it is dark, the stored light is slowly released in the form of a glow"
  • "Glow in the Dark products contain phosphorus…it needs to be exposed to light before it can work"
  • "Radium glow produces light on its own through a chemical process."

All of these claims are mistaken.

1. Luminescent materials do not store light. Light cannot be stored, it is a form of electromagnetic radiation. (In LASERS light is contained within a cavity by reflecting it back and forth by mirrors, but phosphorus is not able to do anything like this.) When the radiation is absorbed by a photoluminescent material the radiation ceases to exist. Because the molecules of the absorbing material are excited into a higher energy state, new electromagnetic radiation (light) may later be emitted – but it is not light that has been stored. (The energy transferred to the luminescent material by the radiation may be considered as stored: but not the light).

2. The process of photosynthesis does not involve "the ability to absorb and store surrounding light" – absorb, yes, but the light is not stored – it ceases to exist once absorbed.

3. Materials which absorb energy from radiation, and then release it slowly ('glow') are called phosphorescent. This does not (only) occur 'when it is dark', but from immediately after irradiation. (The process occurs regardless of whether it is dark enough to observe.)

4. Phosphorus is not itself a phosphorescent material. The glow seen around white phosphorus is due to a chemical reaction with oxygen in the air. Not only does this not store any light, but, also, it does not need light to initiate.

5. Radium does NOT produce light through a chemical process. Radium is radioactive. It undergoes radioactive decay (due to a change in the atomic nucleus). This is NOT considered a chemical process.

Now I turn to what I consider a more serous problem with your site.

Potentially dangerous misinformation

The more serious matter concerns your claim that to be selling products containing 'non toxic' phosphorus:

  • "Glow in the Dark products contain phosphorus (a non toxic substance) which has the ability to absorb and store surrounding light…"
  • "Phosphorus is non toxic and safe for general use."
  • "Phosphorus is a natural mineral found in the human body. Phosphorus Glow in the dark products is perfectly safe for everyday use"
  • "Many get confused and associate all green glow products to be radioactive. This is not true. Phosphorus glow is non toxic and non radioactive."

You may wonder why I think this matters enough to contact you.

It is very misleading to suggest to people reading the site (which could include children who might well be interested in glow-in-the-dark toys) that phosphorus is harmless, and this is completely wrong.

Phosphorus is not found as a natural mineral, as it is much too reactive to be found native (that is, as phosphorus) on earth – although many minerals are compounds of phosphorus (and thus do NOT share its chemical properties), and so sources of the element for use in agriculture etc. The human body does contain compounds of phosphorus, notably in the bones, but again there is no phosphorus (the substance phosphorus) in the human body – if you introduced some it would very quickly react. Sources of phosphorus are important in the diet, but it would be very unwise to try to eat phosphorus itself.

Phosphorus can be obtained in different forms (this is called allotropy where the same element can have different molecular structures – like graphite and diamond both being pure forms – allotropes -of carbon). Some allotropes of phosphorus are not especially dangerous. However, the form which glows is white (or yellow) phosphorus, and this is a very hazardous material.

So, handling phosphorus is dangerous and needs special precautions. (If you really did use phosphorus in your products, I imagine you would know that?) Here is some information from authoritative websites

"Ingestion of elemental white or yellow phosphorus typically causes severe vomiting and diarrhea [diarrhoea], which are both described as "smoking," "luminescent," and having a garlic-like odor. Other signs and symptoms of severe poisoning might include dysrhythmias, coma, hypotension, and death. Contact with skin might cause severe burns within minutes to hours…"

US Centres for Disease Control

"White phosphorus is extremely toxic to humans, while other forms of phosphorus are much less toxic. Acute (short-term) oral exposure to high levels of white phosphorus in humans is characterised by three stages: the first stage consists of gastrointestinal effects; the second stage is symptom-free and lasts about two days; the third stage consists of a rapid decline in condition with gastrointestinal effects, plus severe effects on the kidneys, liver, cardiovascular system, and central nervous system (CNS). Inhalation exposure has resulted in respiratory tract irritation and coughing in humans. Chronic (long-term) exposure to white phosphorus in humans results in necrosis of the jaw, termed "phossy jaw."

US Environmental Protection Agency

Please feel free to check on this information for yourself.

However, I recommend you change the information on your website. In particular, please stop suggesting that phosphorus is a safe, non-toxic material, when the form of phosphorus which glows is highly toxic. I trust that now this has been brought to your attention, you will appreciate that it would be highly irresponsible for you to continue to advertise your products using misleading information about a hazardous substance.

Best wishes

Keith

Batteries – what are they good for?

Okay, 'energy storage' – but what else are they good for?

Keith S. Taber

I was struck by an item on the BBC Radio 4 news headlines at 09.00 this morning (27th Feb. 2023):

"The collapsed battery maker Britishvolt which went into administration last month has been bought by an Australian company.
The new owners will focus initially on batteries for energy storage rather than electric vehicles."

BBC Radio 4 news item

Now on reflection, this was an ambiguous statement. I heard it as

"The new owners will focus initially on batteries for

  • energy storage, rather than
  • electric vehicles."

Which immediately provoked in my mind the question what batteries might be used for in electric vehicles – if not 'energy storage'?

It is possible to charge up an electric car because it includes a battery
(Image by Sabine Kroschel from Pixabay)

Conceptions of energy

Now, this whole area is, metaphorically, a bit of a linguistic minefield as when people say batteries they do not usually distinguish between an individual cell and a battery (of cells). Traditional electrochemical cells we are familiar with have a specific and usually modest e.m.f. – 1.5V or 1.2 V for example. The old 6V and 9V batteries that used to be commonly sold for many purposes (before the switch to most appliances having internal batteries) would be batteries of cells connected in series to work together to provide (1.5V + 1.5V + 1.5V + 1.5V = ) 6V (or whatever). Car batteries were traditionally batteries of lead-acid cells connected together. If each cell has an e.m.f. of 2V, then a dozen connected in series (i.e., the battery) offers 24V.

Moreover, energy is a highly abstract idea, such that even physics teachers do not always agree on how to describe it – the model of energy coming in a number of flavours, 'forms', and processes involving transformations in the form of the energy (e.g., a filament lamp converts electrical energy into heat energy) that many of us learnt (and some of us taught) has come to be seen as misleading and unhelpful by some (it not all) educators. Oh, and if you think I made a mistake there and forget that a lamp produces light energy – not at all. In the 'forms of energy' typology, heat is energy transferred due to a difference in temperature – so that covers all the radiation being emitted by the hot filament.

No wonder, that energy is a common topic for student alternative conceptions, as energy permeates (so to speak) all areas of science, but is a highly abstract notion.

Read about conceptions of energy

An alternative hearing?

Yet, I realised that the statement I had heard was ambiguous and could be parsed differently. It perhaps meant

"The new owners will focus initially on

  • batteries for energy storage

rather than

  • electric vehicles."

That is, I was putting my imaginary brackets in the wrong place and perhaps the company had previously intended to build complete electric cars and not just the batteries? If so, the news was not

  • The new owners will focus initially on batteries (for energy storage rather than electric vehicles).

but rather that

  • The new owners will focus initially on (batteries for energy storage) rather than (electric vehicles).

If this was the intention, it might have been better to have assumed listeners would know that batteries were used for 'energy storage', and to have simplified the statement to

"The new owners will focus initially on batteries rather than electric vehicles."

Batteries for under-performing sports cars?

That made more sense, as surely the BBC's news journalists do not think electric batteries in cars are used for something other than 'energy storage'. So, I checked on the BBC news website, where I found

"The company intends to start by focusing on batteries for energy storage and hopes to have those products available by the end of 2025.

It then intends to produce batteries for high-performance sports cars."

https://www.bbc.co.uk/news/business-64754879

So, I did not misinterpret the news item. According to the BBC (and to be fair, they are probably just reporting, albeit uncritically, what they have been told) under its new owners Britishvolt will

  • first work on batteries that can be used for energy storage, and
  • then shift attention to batteries for sports cars.

My best guess is that "batteries for energy storage" is shorthand for large scale devices for long term storage (that could, for example, be charged by wind generators when it is windy, and then later fed into the National Grid at times of high power demand). The characteristics of these devices would surely be different in detail from batteries used in electric vehicles.

However, I am pretty sure that "batteries for high-performance sports cars" also need to provide 'energy storage' or else those cars are not going to offer the kind of performance Britishvolt and the car manufacturers they will supply are looking for. After all, besides 'energy storage', what else are batteries actually good for?

Another late night writing copy in the newsroom?
(Image by mohamed_hassan from Pixabay)

Planting false memories – autonomously

My fantastic night among the stars

Keith S. Taber

accounts of our memories are like meticulously made reports in laboratory notebooks of carefully observed results obtained by using poorly calibrated apparatus designed for a different type of experiment. They may faithfully reproduce information, but that information is not entirely reliable.

Is remembering something a sufficent reason to believe it happended?

I came to the realisation that something I had remembered, was not actually something that had happened. I had experienced it as a genuine memory – but on reflection soon afterwards I knew full well it was not the case (indeed, could not have been the case). This could have been rather disconcerting in other circumstances. That is, if this had occurred during what we consider a normal state of consciousness. Even so, it gave me pause for thought.

Memories and false beliefs about memory

Memory is one of these things we all know about, but tends to be generally poorly understood. Nomenclature such as 'remember', 'recall', and 'forget', are part of the mental register – the set of terms that are used in everyday discourse to talk about mental experience and related phenomena (Taber, 2013). Our familiarity with this kind of talk probably encourages most of us to feel we have a pretty good handle on the basis of what memory is; what remembering is; and what it means to forget.

Yet, actually, this is not generally so. Research shows that even when people recall events with clarity and are confident in the accuracy of these recollections, their memories may not be trustworthy. Certainly much of what we remember is basically sound (though I am not sure anyone has a good estimate of just how much!) But details often get changed. And sometimes, more than just details.

Read about memory

Memory as abstraction

We represent experience in memory but this is not usually akin to making a video record (even if some people experience their memories as if watching a recording). Memory (the faculty) seems to have evolved to give us an abstracted, generalised impression of past experience. From an evolutionary perspective, we have inherited the kind of memory that was selected for in the context of how our ancestors lived.

Related experiences are often represented without proper discrimination. So, if you regularly get the train to work, you have a memory of this – but not discrete memories of each separate occasion. At least, not unless you are one of those rare people who have been gifted, or perhaps cursed (Luria, 1987), with an eidetic memory. Arguably, for most purposes, a generalised memory of a much repeated scenario is more useful than a large set of records of similar events distinguished by variations in incidental detail. There is value in remembering how to make a cup of tea or unlock a door: less so in having a record of each time one has made tea or unlocked doors.

Memory as a reconstruction

Research shows that memories are often in part constructed – representations ('in memory') activated in remembering offer a partial account, which is filled-in with feasible details BEFORE the memory is presented to consciousness. The person reporting the memory does not know which elements were actually recalled, and which then added.

This has been shown, for example, by testing people a few days after they have been told an unfamiliar story. Typically, people get some points correct, forget some details, but also change details, or even add material that was never in the original. But the person 'remembering' (actually, reconstructing) the story does not necessarily have any less confidence in the fabricated elements, as they have been integrated into the account pre-consciously: 'out of mind' so to speak. Reports of memories are usually honest – it is just that they are honest reports of imperfect memories. Eye witness testimony is famously unreliable, but not because most people lie.

In this way, accounts of our memories are like meticulously made reports in laboratory notebooks of carefully observed results obtained by using poorly calibrated apparatus designed for a different type of experiment. They may faithfully reproduce information, but that information is not entirely reliable. We cannot trust such results just because someone provides an honest report of what was noted down in the record.

Memories are somewhat like those historical reconstructions based on incomplete accounts filled in by a dramatist to offer a full narrative for the viewer, perhaps with some scenes moved to locations that seem to be more keeping with the overall progression of the storyline (or are just considered more visually compelling). Crick and Watson may not have had those specific conversations as portrayed when walking across the backs, or in The Eagle, but there is a sense in which the story has greater coherence and truth if shown that way. Not a strict, historical, truth, of course – but perhaps it creates a better mythology, or acts as more effective pedagogy, or just offers a better aesthetic?

"Look, according to the script here, they are going to film us having this conversation on the tennis court."
(Tim Pigott-Smith as Francis Crick and Jeff Goldblum as Jim Watson in a still from the 1987 Horizon special docudrama, 'Life Story' {a.k.a. 'The Race for the Double Helix'}.)

Memories are not fixed. Each time you activate a memory you change the trace. It is therefore possible to 'plant' memories. The first time you are asked to recall the crime scene you are asked if you saw a knife and report not. But when asked again at a later date, you may now associate a knife with the scene (as you had been invited to think about it in that context previously, the image has got linked to the memory). This can be done deliberately, but criminal investigators have to be very careful of accidentally planting memories.

People sometimes recall events from very early in their lives at an age research suggests is before distinct autobiographical memories can be laid down. Presumably, what is actually being remembered is having previously imagined the scene years before when told about it.

I can picture myself in my pram telling enquiring passers-by my name and address – but that is actually my memory of a report of someone else's memory. I almost believe I recall escaping from my playpen by emptying out the toy box and turning it upside down to act as step. But that could be a fabrication I have been fed. I do know these are memories of stories about me and not actual memories of the events, but perhaps some of my actual early memories of events were also 'planted' without my being aware of this?

It is all in the mind

After all, what we actually recall is a representation of our experience, which is effectively mental. We have mental experiences when we are out acting on the environment (e.g., walking in the woods) – but also when watching a film, or listening to a story, or simply daydreaming. And, indeed, we also have mental experiences when we sleep.

Researchers have found children giving convincing and committed accounts of how when they were younger

  • they had to attend hospital for a minor emergency, or
  • when they drifted away from caregivers at the shops and got lost

although these were imaginary events which the researchers themselves had previously planted, and which parents confirmed did not reflect any actual event the child had experienced. (Such research raises ethical issues – now we know memories can be suggested by researchers, is it ethical for investigators to continue to carry out such studies? If so, what are the limits on the kinds of memories it is acceptable to try and plant?)

False memory syndrome

A very serious consequence of this phenomenon has been the recognition that accusations against parents and teachers and other caregivers of child abuse can arise from the inadvertent planting of false memories when children are questioned. Careful probing of the children's memories may be needed over sequences of interviews. Unfortunately, that very scenario also provides suitable conditions for leading questions to plant false memories.

Identifying cases of child abuse can be especially challenging as young children may not understand what has happened to them (especially in cases of sexual assaults) and/or may be traumatised. Young children are also less able to distinguish memories of real and imaginary events.

Recalling previous mental states

There is a procedure undertaken in psychology where a youngster is shown a biscuit box, say, and asked to guess its contents. For example:

Cookies.

The child is then shown that the box actually contains something incongruous:

Pebbles!

They are then asked what they had thought was in the box when first shown it, before they saw inside:

Pebbles, of course.

This is normal behaviour. The child gives what for them is a genuine response – but it is false. It is not a lie – it would hardly be convincing if it was. With maturation a child becomes able to distinguish what I think now from what I thought before – but below a certain age this distinction is simply not available.

That particular result is specific to young children, but a degree of memory distortion is normal for the rest of us – indeed the best of us, according to the historian/philosopher of science Thomas Kuhn,

"Not always, but quite usually, scientists will strenuously resist recognising that their discoveries were the product of beliefs and theories incompatible with those to which the discoveries themselves gave rise."

Kuhn, 1984/1887

Kuhn was not suggesting that scientists were seeking to claim a prescience they did not have, but simply that they too are effected by the difficulty of returning to an earlier state of ignorance before they slowly built a more nuanced and deeper understanding of a field. The instrument they used to expand their understanding – their prior understanding – was the very thing that was being modified. That is something teachers need to bear in mind – many of those things that now seem obvious and straightforward to the expert were obscure and complex when met as a novice.

The dilemma of 'recovered' memories of abuse

It is obviously imperative to detect and stop sexual abuse, but it became clear that in some communities there seemed to be an inordinate amount of such child abuse going on, often involving strange rituals more at home in a Hammer Horror film. Children who were perfectly happy at home were being separated from their families on the basis of an investigative methodology which unfortunately created the 'evidence' of abuse (and made it indistinguishable from any real memories of actual abuse).

Some adults in therapy also found they gradually uncovered (or perhaps, actually, gradually constructed) previously undetected memories of childhood abuse, and consequently became estranged from parents that they now labelled abusers. Of course, such 'recovered' memories could be real, but sometimes they were not, and unfortunately recall does not come with metadata tags to tell us how and when what is being recalled was first represented in memory.

How is it possible that adults might live for decades without any conscious awareness that their parents had abused them as children, only for this to come to light when they entered into a psychoanalytic relationship with a therapist? Supposedly, the memories of something so awful, and often inconsistent with an otherwise happy family life, had been repressed.

There are different views on whether false memory syndrome leading to fabricated accusations of abuse is very widespread as has sometimes been claimed (an 'epidemic'), or is just an occasional aberration (Goodman, Gonzalves & Wolpe, 2019; Otgaar, Howe & Patihis, 2022). The challenge is that when there is nothing to corroborate memory with, then all we have is the memory; and memory is fallible and susceptible to distortion.

Memories are like conceptions

The research into student conceptions in science makes it clear that a learners' knowledge of a topic does not exist on a single dimension from ignorance to knowledge – they can have knowledge that is more or less complete, but also alternative conceptions that are more or less canonical. In a similar way, memories can also be more or less complete, but also more or less accurate – indeed, more or less fabricated.

Memory and sleep

We know that sleep is essential to good health and, indeed, that healthy sleep must include dreaming. It is normal to dream every night, although we may only remember dreams if they occur just before waking. Clearly, sleep must be physiologically important as sleeping involves taking the significant risk of losing awareness of our environment when, for example, predators may be around.

Sleeping leaves us vulnerable. Of course, some creatures are less vulnerable than others when they nod off. (Image by PublicDomainPictures from Pixabay)

One of the areas that sleep is considered to support is memory consolidation. That is, without good sleep, our ability to update and maintain our memories suffers. I do not think the details of this are well understood – but the effects of sleep deprivation are well known (such that it can be used as a form of torture).

No one really knows for sure the function of dreams, or whether, perhaps, dreams are just an epiphenomenon, a kind of by-product of the maintenance processes going on in the brain during sleep. There is a very long tradition of trying to read meaning in (or into!) dreams (the story of Daniel in the Bible Old Testament for example) and the interpretation of dreams was a key part of Sigmund Freud's psychoanalysis. Dreams are such a part of our lives, it often seems they must have significance – but there is no strong scientific support to suggest this is so. Given the nature of most of my dreams, I find this reassuring.

Autobiographical and semantic memory

Our memories represent both autobiographical and semantic material. That is, we recall specific events in our lives as well as abstract material such as Ohm's law, the theory of natural selection, or the molecular structure of benzene.

So, if our sleeping brains are maintaining memory function and this involves activating memory traces, and we experience – or make sense of – some of this as dreaming, then why do my dreams involve me in 'social' situations, but I do not (that I can recall) dream about, say, molecular shapes or circuit configurations? After all, August Kekulé supposedly discovered the structure of benzene when he was drifting into sleep.

Does this reflect my lack of genius – would an Albert Einstein or a Richard Feynman dream in abstract mathematical symbols? I do not, at least, not that I notice. Generally my dreams are very mundane, which is why one of last night's dream's seemed out of place.

A dream party (no teaching involved)

I was at a kind of Hollywood-type party – a party attended by many of those who would be labelled by the general public as 'stars'. To be fair, I did not recognise (or perhaps, better, actually notice) who most of the people there were: rather I just had the impression that these were 'stars'.

I should point out that I do not tend to go to those kinds of parties (obviously, I do not tend to be invited to them), and indeed I am not really one for parties. So, I am not sure why I was dreaming about being at one.

More typically, my dreams involve teaching situations. Yet, I never actually teach anything substantial in these dreams – more often I am

  • getting myself ready to teach a class,
  • organising a class to get ready to work, or
  • on my way to teach a class (which for various reasons never gets started)

as if my dreaming brain has access to autobiographical material, but does not know any chemistry or physics or research methodology or anything I might actually teach. It seems as if I do not have access to my semantic knowledge for use in my dreams. This raises an interesting question.

  • If dreaming is considered to support the processes of memory consolidation – why do we not dream about the material we are learning?

(And although I am not taking any formal classes – I read books and listen to podcasts which would provide plenty of subject matter.)

  • Is it just that this processing happens at a more abstract level that we cannot picture directly in dreams?

Why are dreams not more realistic?

What has long intrigued me about dreams is that although I do sometimes dream about my late wife or close family: in general the people in my dreams seem to be made up, like characters in a fiction. I do not dream about students or classes I have taught but rather populate my dreams with fictional people. This seems odd, as when I am awake I can remember many students I have taught and it would seem more economical for my brain to use their images than construct people de novo. 1 Why are my dreams so 'CGI-heavy' (as in 'computer generated imagery') when it is known that requires a lot of processing?

And this is not just people. In my dreams I am in buildings or in streets, etcetera – but when I awake and can recall a dream I realise that the house I was living in, in the dream, is not my house, or any other house I have ever lived in. Or know. (And when there is an exception, the house seems to have been moved! 3)

The classroom in a dream is not one where I taught, even though there are several very familiar classrooms where I taught a great number of lessons over a period of years. The same applies with the teaching institutions more generally – when I move around these buildings in my dreams I use hallways, go to canteens, and the like; pass thought entrance areas. All these things are experienced as familiar to me – in my dreams, the people, rooms and buildings and sometimes even streets and town centres all seem familiar – but only till I wake up. Then it is immediately clear they were constructed – in effect imagined – and not recalled from real life. Perhaps they are sometimes recalled from a previous dream, but not recalled from my actual 'awake' life. They are familiar in sleep – but not known from my waking life.

[There is a theory that we live to dream. Our real lives, the lives that really matter, are the lives we have in sleep when we dream. In order to maintain these meaningful lives we need the support period when we are awake and eat and, so forth. From this perspective, the question of why we dream disappears. Instead we might ask why we need to be conscious when awake: presumably this makes it easier to find sustenance, mates, shelter and the other things that allows us to continue the human lineage, and to regularly settle down for a good night's sleep.]

There are exceptions. Once when younger and at my parents house, I dreamt that I flew out of their house down the road, turning into the adjoining road then right at a junction into another road that led to the local shops, over the roundabout and headed down to town. I will not bore you with the details except to say the flight was exhilarating rather than scary…and was (certainly, subjectively seemed) detailed. I saw the roads and buildings in detail, and, as far as I could tell when I awoke, accurately. This seemed to me more memory than imagination…with one obvious caveat. In the dream I was seeing everything from maybe 10 metres above the ground looking down. I had walked along those roads hundreds of times, but only from a vantage point of less than two metres above ground level.

Maybe there is a good reason we do not dream realistically too often. When I have had dreams where I interact with real people then I have sometimes become confused later. I have had to realise that 'no, that was just a dream'. If one does not realise on waking, perhaps one would never know of the mistake – but that could have consequences. ("You told me to give the house to Marxist anarchists!")

And awaking from a conversation with a loved one, only to then realise that must have been a dream because the person is no longer with us, is difficult: waking up and realising that was not a real experience, and it could not have been, tends to ratchet the grief process back up a few notches. Spending time with the loved one, only to wake and realise – again – she is gone offers a bitter-sweet counterpoint and reprise to the old adage that it is better to have loved and lost…

All the same, it does suggest that if dreaming is largely a constructive process that requires the brain to design and simulate new but realistic-seeming environments and populate them with convincing androids, then that is an awful lot of mental work. Perhaps it calls upon 'memories' at some level, but it seems largely the work of imagination.

Transitioning to sleep

I had slept for about four hours, but then awoke wishing to use the bathroom. That is not unusual, and more often than not I crawl back into bed and straight back to sleep. On this occasion I just lay there waiting to drop off again. I can often tell when I am about to go to sleep as my visual cortex does its version of the iTunes visualiser and I see various shapes and colours gradually appear and then start moving around. Sometimes, not. But I have a strategy to avoid lying awake worrying that I am not asleep. I go on adventures.

So, I take sea voyages, and spend time relaxing on my private tropical island with its bananas, coconuts and pineapples – I have built quite a repertoire of scenarios I slowly develop knowing that usually the story does not get very far before I drift off somewhere else. (That is, I have represented in memory my previous imagined experiences of my repertoire of getting ready for sleep scenarios.)

However, this time my body did not seem to want to go back to sleep, and I seemed to still be lying awake waiting for sleep hours later. This went on so long I could eventually hear the voices of others in the house, now up to start the day; and eventually they were even leaning over me in bed to try and get access to the breakfast things. (That should have been a clue, even if my sleeping self had forgotten there was no one else in the house.)

Then, I was at the party.

I 'remembered' (…in my dream…) that Elton and I go back a long way
(Elton publicity shot accessed from Wikimedia, with apologies to Bernie)

My friend, the superstar

I did not really know the people there – I do not mix in these circles.

But then I saw Sir Elton John, and realised there was someone at the party that I did know well. Elton greeted me, and at that moment I recalled how we regularly engaged in repartee on the morning radio show. In that instant, Elton being there and acknowledging me, fitted with a long-standing and familiar part of my life.

Except, of course, this was completely fabricated. I have never met Sir Elton, and the Elton in my dream was for some reason Elton from the 1980s. And I certainly do not appear on any morning radio show, with or without him. Elton (I am pretty sure) does not know I exist, and would not be seeking me out at the kind of parties that I do not in any case go to, and that I would not be invited to (and that I would not really want to go to even if I was invited. Though meeting Elton would be cool.)

So what? This is just a dream – so, it is not real. I do not usually dream of celebrities. (Though Joe Root tuned up in a dream a while back.2)

Why Elton? I have no idea. I do have a lot of his records and rate him highly as a songwriter/singer/pianist. But my dreams would be pretty crowded if all the musicians who moved me made an appearance. 4 Perhaps I just associate Elton with glitzy parties – and I did not spot Freddie was over the far side of the room.

But that was not the point that really struck me. It was rather a phenomenon that I have noticed before about dreams: that one is in a scenario where something needs explaining (here, Elton greeting me as a friend) and there is an immediate in-fill of backstory which is experienced in the dream as authentic recall. Our brains (i.e., we) are able to make up stuff, and present it to us, and convince us that it is what we have previously experienced: here regular jovial exchanges with Elton on a non-existent radio show. In the waking world (where I am well aware that I do not move in those kinds of circles) I immediately saw through this, but in the context of the dream I simply accepted the false memory as being a genuine, recalled, experience.

So, what is to say something similar is not happening regularly in my waking life?

Almost a century ago, the experimental psychologist Frederic Bartlett (1932/1995) concluded from his empirical studies on memory that the three phenomena we consider separately as perceiving, remembering, and imagining, were not so discrete and separate at all.

Perception, imagination, and memory are generally considered separate mental faculties – but are probably not as distinct as we tend to think

What we think we see or hear is strongly framed by (memory of) previous experiences. What we can imagine is resourced by (memory traces of) what we have experienced – what we have seen and heard in the past. What we think we remember is often fragmentary data filled-out with imaginary components that seem (on the basis of our general experience of the world, i.e., a kind of memory) feasible. What we remember may be based on what we have experienced, or what we have previously imagined we have experienced, or even what has been suggested to us in the past as something we have experienced. The memory that seems so genuine and convincing may be filled-in by guesswork, and may indeed be a memory of something other than a real experience.

Probably, we all live with false memories that we never have reason to question and discard. (Perhaps some of them even do a great deal of good work in supporting our self-esteem and self-worth? Or, perhaps, the opposite?)

Based on past experience, at least as I remember it(!), the Elton dream was atypical, as it involved a real person rather than the usual rolling cast of fictional characters. (But see notes 2 and 4) Perhaps that is just as well, as we are less likely to misconstrue recollections of dreams involving imaginary people in imaginary places as being memories from our waking lives. So, I probably will not meet any stars in my dreams tonight. However, just in case, I wonder if Kate Bush is free?

See you in my dreams?

Work cited:

  • Bartlett, F. C. (1932/1995) Remembering. A study in experimental and social psychology. Cambridge; Cambridge University Press.
  • Goodman, G. S., Gonzalves, L., & Wolpe, S. (2019). False memories and true memories of childhood trauma: Balancing the risks. Clinical Psychological Science, 7(1), 29-31.
  • Kuhn, T. S. (1984/1887) Afterword: Revisiting Planck, in Black-Body Theory and the Quantum Discontinuity, 1894-1912. With a new afterword (pp.349-370). The University of Chicago Press.
  • Luria, A. R. (1987). The Mind of a Mnemonist: a little book about a vast memory. Harvard University Press.
  • Otgaar, H., Howe, M. L., & Patihis, L. (2022). What science tells us about false and repressed memories. Memory, 30(1), 16-21.
  • Schacter, D. L. (Ed.). (1995). Memory Distortion. How minds, brains, and societies reconstruct the past. Harvard University Press.
  • Taber, K. S. (2013). Modelling Learners and Learning in Science Education: Developing representations of concepts, conceptual structure and conceptual change to inform teaching and research. Dordrecht: Springer.

Notes

1 This question vexes me when I also consider that I believe that, in a sense, I do not directly interact any other real people. By that, I mean, that although I seem to be, say, talking to a person in the external world, I only have direct experience of a simulation of them constructed in my brain based on sensory data and past experience. We all (I assume?) have mental conversations with people we know well when they are not present: we think we know what they would say in a situation: how they would react; what they might suggest. When they are [actually, physically] present we are surely engaging the same simulation, just with a modest drip feed of sensory data blending in.

(Does that sound strange? I think it would be more strange that if you have been married for 20 years you would assume that you base your interaction with a spouse primarily on transient and likely incomplete immediate sensory data rather than the detailed mental simulation of them that you have incrementally and iteratively built up over hundred of hours of past experience.)

If I call upon those simulations deliberately when asking myself "what would X think about this?", why not in my dreams? (Perhaps, I suggest above, as realistic dreams that are remembered would too readily be confused with waking experience.)

If my simulation argument seems unconvincing, ask yourself why you feel you are engaging with the same person

  • when you meet them under different conditions (lighting, background noise);
  • when you only see a two-dimensional image on a small flat screen; or even
  • when you only have a low quality reproduction of their voice coming from a tiny speaker?

It is not because the sensory data matches well in these different situations.

2 This is my note of my dream involving cricketer Joe Root

I awoke 3 from a dream where I'd been watching sport – football, and switched to cricket [at this point I seem to be watching television], there was a run out call. English bowler, never seen before, seemed to hesitate as he picked up the ball, but direct hit on wicket – awaiting replays to see if it was a run out.

Joe Root was watching next to me on the grass (this was just after it had been announced he was standing down as test team captain) but seemed fidgety – he was moving about and taking up yoga-like positions. [Note, I am now actually at the cricket match, not watching TV.]

There were two young women, girls really, wearing Summer gear (shorts, top tied up high so bare stomach area). They were exchanging glances, and edging closer to Joe. Eventually he did some kind of flip, and landed on one of the girls who had moved up close behind him.

Giggles.

I joked that this was a litigation issue and he might be sued for millions.

Report of a dream [this is a purely imaginary account and in no way reflects any real (waking!) event involving Joe Root that I am aware of!]

Why Joe Root? Just because he had been mentioned in the news? Perhaps. However Root was involved in two of my own alternative conceptions (we have them in all areas of knowledge, not just science), and in both cases I had sensed there was something I was missing in the particular situation – so, perhaps it might be said I felt some 'cognitive dissonance' until I realised my misunderstandings.

One of these misconceptions concerned advertising for pet insurance* that often featured Root alongside a dog, by a company who sponsored some of the cricket highlights on television. It struck me as odd that this company could afford to air so many adverts employing a leading sportsman when I could not imagine the market for pet insurance was especially lucrative. It eventually dawned on me (many months later) that the company were advertising insurance for people – not pets. Perhaps the dog was meant to represent health (rather than, as I had assumed, a creature likely to soon need veterinary attention). [* Note, my clear memories of regularly seeing advertisements for pet insurance turned out to be unreliable as I had misconstrued the sensory data that became represented in memory.]

The other misconception concerned the regular occurrence of booing of Root on the cricket field. Generally cricket crowds do not boo – although fast bowler Stuart Broad had incurred the wrath of Australian supporters who had taken to booing him. But Root, an English international cricketer, seemed to get booed at English grounds whenever he went out to bat, or when he hit a boundary, even though I was not aware of anything he had done or said likely to offend. And, indeed, from after-match interviews I had seen, I thought he did not seem like a person who would offend a large proportion of spectators. Indeed, he was always polite, and sensible, and modest. Again, it took quite a while before I realised that what I was hearing as "bo:o" was actually the crowd calling out an extended "ro:ot".

3 Actually, this is part of a longer account I noted down because it involved a dream within a dream. The account continues:

I woke up, and went downstairs, and went to the table I use as a desk at the front of the house. Looking out I saw the house opposite [which should have been obscured by my garden hedge] had no door and looked like they were having workers in to put in a new door. Then I realised that the house as a whole (which was much larger than usual, and all red brick [unlike the actual house opposite]) was not finished, and looking around I realised that none of the houses in the street were finished yet. I noticed there was no computer on my desk. I went to look out of the back of the house and saw rolling hills and countryside – it look like the West Country around Bristol. I realised I must still be asleep, and found some paper to write down the dream so I could have a record when I really wake (!). Found a pen but it did not seem to work very well.

So, if I can wake up from one dream within another dream, perhaps I am not actually awake now?

4 I have a note of the guitarist/composer Steve Hackett appearing in one dream that was part of a sequence of scenes I recalled when I awoke,

2. Hackett was in an office with charts/manuscripts for music he intended to play for a concert, and in discussion over whether to bring in a second guitarist to play some parts. A person advising – 'manager'(?) of the venue – was going to play some of the music there in the office.

I am not sure what triggered that, although the previous scene that I recalled was unusual (for me) in that it was an auditory dream5:

  1. listening to the first Genesis album ('From Genesis to Revelation') and noticing atmospheric instrumental passages with subtle electric guitar parts I'd never noticed before

I had not noticed these passages before, because – of course- they are not actually on the album! Steve Hackett did not join Genesis till after that album, but perhaps my sleeping brain was thinking that these were contributions he might have made if he had been in the band then?

5 Again, it seems odd that as much of my waking life is accompanied by music, I seldom dream of music. Indeed the first time I recall this happening I was so struck by the dream that I still recall the occasion over 40 years later. I was about 17 and I had fallen asleep one Sunday afternoon, after a having been up late the night before as someone in the sixth form had had a party. (No, Elton was not there – at least, as far as I recall!) I dreamed what seemed to me at the time a very vivid and detailed rendition of 'Shine on you crazy diamond' by Pink Floyd.

Of course, that is just my recollecti0n of my subjective experience on waking from sleep (that is, the waking memory of the dream) – but the music had (at least) seemed so real and intense and deep that, all these years later, I still remember the effect such a detailed dream had on me when I awoke.

Are the particles in all solids the same?

Particle intuitions may not match scientific models

Keith S. Taber

Sophia was a participant in the Understanding Science Project. I first talked to her when she was in Y7, soon after she began her secondary school course.

One of the first topics she studied in her science was 'solids, liquids and gases', where she had learnt,

that solids are really hard and they stay together more, and then liquids are close together but they move around, and gases are really free and they just go anywhere

She had studied a little about the topic in her last year of primary school (Y6), but now she was being told

about the particles…the things that make – the actual thing, make them a solid, and make them a gas and make them a liquid

Particle theory, or basic kinetic theory, is one of the most fundamental theories of modern science. In particular, much of what is taught in school chemistry is explained in terms of theories involving how the observed macroscopic properties emerge from the characteristics and interactions of conjectured sub-microscopic particles that themselves often have quite unfamiliar properties. This makes the subject very abstract, challenging, and tricky to teach (Taber, 2013a).

Read about conceptions of atoms

Particle theory is often introduced in terms of the states of matter. Strictly there are more than three states of matter (plasma and Bose-Einstein condensates are important in some areas of science) but the familiar ones, and the most important in everyday phenomena, are solid, liquid and gas.

The scientific account is, in simple terms, that

  • different substances are made up of different types of particle
  • the different states of matter of a single substance have the same particles arranged differently

These are very powerful ideas, even if there are many complications. For example,

  • the terms solid, liquid and gas only strictly apply to pure samples of a single substance, not mixtures (so not, for example, to bronze, or honey, or, milk, or ketchup, or even {if one is being very pedantic} air or sea water. And cats (please note, BBC) are completely inadmissible. )
  • common salt is an example of a pure substance, that none-the-less is considered to be made up of more than one type of particle

This reflects a common type of challenge in teaching science – the full scientific account is complex and nuanced, and not suitable for presenting in an introductory account; so we need to teach a simplified version that introduced the key ideas, and then only once this is mastered by learners are they ready to develop a more sophisticated understanding.

Yet, there is a danger that students will learn the simplified models as truths supported by the authority of science – and then later have difficulty shifting their thinking on. This is not only counter-productive, but can be frustrating and de-motivating for learners who find hard-earned knowledge is not as sound as they assumed.

One response to this is to teach science form very early in a way that is explicit about how science builds models of the natural world: models that are often simplifications which are useful but need to be refined and developed to become powerful enough to expand the range of contexts and examples where they can be applied. That is, students should learn they are being taught models that are often partial or imperfect, but that is just a reflection of how science works, developing more sophisticated understanding over time (Taber, 2017).

Sophia confirmed that the iron clamp stand near where she was sitting would have particles in it, as would a lump of ice.

Are they the same particles in the ice as the iron?

Yeah, because they are a solid, but they can change.

Ah, how can they change?

Cause if, erm, they melted they would be a liquid so they would have different particles in.

Right, so the iron is a solid, 

Uh hm.

So that's got one type of particle?

Yeah.

And ice is also a solid?

Yeah.

So that has the same sort of particles?

Yeah, but they can change.

The ones in the ice?

Mm,

To a learner just meeting particle theory for the first time, it may seem just as feasible that the same type of particle is found in one state as in one substance.

In the scientific model, we explain that different substances contain different types of particles, whereas different states of the same substance contain different arrangements of the same particles: but this may not be intuitively obvious to learners.1 It seemed Sophia was thinking that the same particles would be in different liquids, but a change of state led to different particles. This may seem a more forced model to a teacher, but then the teacher is already very familiar with the scientific account, and also has an understanding of the nature of those particles (molecules, ions, atoms – with internal structure and charges that interact with each other within and between the particles) – which are just vague, recently imagined, entities to the novice.

Sophia seemed to misunderstood or misremembered the model she had been taught, but to a novice learner these 'particles' have no more immediate referent than an elf or an ogre and would be considerably more tenuous than a will-o'-the-wisp.

Sophia seemed to have an alternative conception, that all solids have one type of particle, and all liquids another. If I had stopped probing at that point I might have considered this to be her thinking on the matter. However, when one spends time talking to students it soon becomes clear that often they have ideas that are not fully formed, or that may be hybrids of different models under consideration, and that often as they talk they can talk themselves into a position.

So, if I melted the ice – that changes the particles in the solid?

Well they are still the same particles but they are just changing the way they act…

Oh.

How do they change?

A particle in a liquid [sic, solid] is all crammed together and don't move around, but in a liquid they can move around a little but they are still close and, can, you can pour a liquid, where you can't a solid, because they can move in. 

Okay, so if I have got my ice, that's a solid, and there are particles in the ice, and they behave in a certain way, and if the ice melts, the particles behave differently?

Yeah.

Do you know why they behave differently in the liquid?

No. {giggles} So, they can, erm

• • • • • • • • • • • •  [A pause of approximately 12 s]

They've more room cause it's all spread out more1, whereas it would be in a clump

The literature on learners conceptions often suggests that students have this or that conception, or (when survey questions are used) that this percentage thinks this, and that percentage thinks that (Taber, 2013b). That this is likely to be a simplification seems obvious is we consider what thinking is – whatever thought may be, is it a dynamic process, something that moves along. Our thinking is, in part, resourced by accessing what we have represented in memory, but it is not something fixed – rather something that shifts, and that often becomes more sophisticated and nuanced as we explore a focus in greater depth.

I think Sophia did seem to have an intuition that there were different types of particles in different states of matter, and that therefore a change of state meant the particles themselves changed in some way. As I probed her, she seemed to shift to a more canonical account where change of state involved a change in the arrangement or organisation of particles rather than their identity.

This may have simply been her gradually bringing to mind what she had been taught – remembering what the teacher had said. It is also possible that the logic of the phenomenon of a solid becoming a liquid impressed on her that they must be the same particles. I suspect there was a little of both.

When interviewing students for research we inevitably change their thinking and understanding to some extent (hopefully, mostly in a beneficial way!) (If only teachers had time to engage each of their students in this way about each new topic they might both better understand their students' thinking, and help reinforce what has been taught.)

Did Sophia 'have a misconception'? 1 What did she 'really think'? That, surely, is to oversimplify.

She presented with an alternative conception, that under gentle questioning she seemed to talk /think herself out of. The extent to which her shift in position reflected further recall (so, correcting her response) or 'thinking through' (so, developing her understanding) cannot be known. Likely there was a little of both. What memory research does suggest is that being asked to engage in and think about this material will have modified and reinforced her memories of the material for the future.

Read about the role of memory in teaching and learning

Work cited:
Note

1 Actually, the particles in a liquid are not substantially spread further apart than in a solid. (Indeed, when ice melts the water molecules move closer together on average.) Understanding melting requires an appreciation of the attractions between particles, and how heating provides more energy for the particles. This idea of increased separation on melting is therefore something of an alternative conception, if one that is sometimes encouraged by the diagrams in school textbooks.

Teaching an introductory particle theory based on the arrangement of particles in different states, without reference to the attractions between particles is problematic as it offers no rational basis for why condensed states exists, and why energy is needed to disrupt them – something highlighted in the work of Philip Johnson (2012).

Misconceptions of change

It may be difficult to know what counts as an alternative conception in some topics – and sometimes research does not make it any clearer

Keith S. Taber

If a reader actually thought the researchers themselves held these alternative conceptions then one could have little confidence in their ability to distinguish between the scientific and alternative conceptions of others

I recently published an article here where I talked in some detail about some aspects of a study (Tarhan, Ayyıldız, Ogunc & Sesen, 2013) published in the journal Research in Science and Technological Education. Despite having a somewhat dodgy title 1, this is a well respected journal published by a serious publisher (Routledge/Taylor & Francis). I read the paper because I was interested in the pedagogy being discussed (jigsaw learning), but what promoted me to then write about it was the experimental design: setting up a comparison between a well-tested active learning approach and lecture-based teaching. A teacher experienced in active learning techniques taught a control group of twelve year old pupils through a 'traditional' teaching approach (giving the children notes, setting them questions…) as a comparison condition for a teaching approach based on engaging group-work.

The topic being studied by the sixth grade, elementary school, students was physical and chemical changes.

I did not discuss the outcomes of the study in that post as my focus there was on the study as possibly being an example of rhetorical research (i.e., a demonstration set up to produce a particular outcome, rather than an open-ended experiment to genuinely test a hypothesis), and I was concerned that the control conditions involved deliberately providing sub-optimal, indeed sub-standard, teaching to the learners assigned to the comparison condition.

Read 'Didactic control conditions. Another ethically questionable science education experiment?'

Identifying alternative conceptions

The researchers actually tested the outcome of their experiment in two ways (as well as asking students in the experimental condition about their perceptions of the lessons), a post-test taken by all students, and "ten-minute semi-structured individual interviews" with a sample of students from each condition.

Analysis of the post-test allowed the researchers to identify the presence of students' alternative conceptions ('misconceptions'2) related to chemical and physical change, and the identified conceptions are reported in the study. Interviewees were purposively selected,

"Ten-minute semi-structured individual interviews were carried out with seven students from the experimental group and 10 students from the control group to identify students' understanding of physical and chemical changes by acquiring more information about students' unclear responses to [the post-test]. Students were selected from those who gave incorrect, partially correct and no answers to the items in the test. During the interviews, researchers asked the students to explain the reasons for their answers to the items."

Tarhan et al., 2013, p.188

I was interested to read about the alternative conceptions they had found for several reasons:

  1. I have done research into student thinking, and have written a lot about alternative conceptions, so the general topic interests me;
  2. More specifically, it is interesting to compare what researchers find in different educational contexts, as this gives some insight into the origins and developments of such conceptions;
  3. Also, I think the 'chemical and physical changes' distinction is actually a very problematic topic to teach. (Read about a free classroom resource to explore learners' ideas about physical and chemical changes.)

In this post I am going to question whether the author's claims in their research report about some of the alternative conceptions they reported finding are convincing. First, however, I should explain the second point here.

Cultural variations in alternative conceptions

Some alternative conceptions seem fairly universal, being identified in populations all around the world. These may primarily be responses to common experiences of the natural world. An obvious example relates to Newton's first law (the law of inertia): we learn from very early experience, before we even have language to talk about our experiences, that objects that we push, throw, kick, toss, pull… soon come to a stop. They do not move off in a straight line and continue indefinitely at a constant speed.

Of course, that experience is not actually contrary to Newton's first law (as various forces are acting on the objects concerned), but it presents a consistent pattern (objects initially move off, but soon slow and stop) that becomes part of out intuitions about the world and so makes learning the scientific law seem counter-intuitive, and so more difficult to accept and apply when taught in school.

Read about the challenge of learning Newton's first law

By contrast, no one has ever tested Newton's first law directly by seeing what happens under the ideal conditions under which it would apply (see 'Poincaré, inertia, and a common misconception').

Other alternative conceptions may be less universal: some may be, partially at least, due to an aspect of local cultural context (e.g. folk knowledge, local traditions), the language of instruction, the curriculum or teaching scheme, or even a particular teacher's personal way of presenting material.

So, to the extent that there are some experiences that are universal for all humans, due to commonalities in the environment (e.g., to date at least, all members of the species have been born into an environment with a virtually constant gravitational field and a nitrogen-rich atmosphere of about 1 atmosphere pressure {i.e., c.105 Pa} and about 21% oxygen content), there is a tendency for people everywhere (on earth) to develop the same alternative conceptions.

And, conversely, to the extent that people in different institutional, social, and cultural contexts have contrasting experiences, we would expect some variations in the levels of incidence of some alternative conceptions across populations.

"Some common ideas elicited from children are spread, at least in part, through informal learning in everyday "life-world" contexts. Through such processes youngsters are inducted into the beliefs of their culture. Ideas that are common in a culture will not usually contradict everyday experience, but clearly beliefs may develop and be disseminated without matching formal scientific knowledge. …

Where life-world beliefs are relevant to school science – perhaps contradicting scientific principles, perhaps apparently offering an explanation of some science taught in school; perhaps appearing to provide familiar examples of taught principles – then it is quite possible, indeed likely, that such prior beliefs will interfere with the learning of school science. …

Different common beliefs will be found among different cultural groups, and therefore it is likely that the same scientific concepts will be interpreted differently among different cultural groups as they will be interpreted through different existing conceptual frameworks."

Taber, 2012a, pp.5-6

As a trivial example, in England the National Curriculum for primary age children in England erroneously describes some materials that are mixtures as being substances. These errors have persisted for some years as the government department does not think they are important enough to make the effort to correct the error. Assuming many primary school teachers (who are usually not science specialists, though some are of course) trust the flawed information in the official curriculum, we might expect more secondary school students in England, than in other comparable populations, to later demonstrate alternative conceptions in relation to the critical concept of a chemical substance.

"This suggests that studies from different contexts (e.g., different countries, different cultures, different languages of instruction, and different curriculum organisations) should be encouraged for what they can tell us about the relative importance of educational variables in encouraging, avoiding, overcoming, or redirecting various types of ideas students are known to develop."

Taber, 2012a, p.9
The centrality of language

Language of instruction may sometimes be important. Words that supposedly are translated from one language to another may actually have different nuances and associations. (In English, it is clearly an alternative conception to think the chemical elements still exist in a compound, but the meaning of the French élément chemie seems to include the 'essence' of an element that does continue into compound.)

Research in different educational contexts can in principle help unravel some of this: in principle as it does need the various researchers to detail aspects of the teaching contexts and cultural contexts from which they report as well as the student's ideas (Taber, 2012a).

Chemical and physical change

Teaching about chemical and physical change is a traditional topic in school science and chemistry courses. It is one of those dichotomies that is understandably introduced in simple terms, and so, offers a simplification that may need to be 'unlearnt' later:

[a change is] chemical change or physical change

[an element is] metal or non-metal

[a chemical bond is] ionic bonding or covalent bonding

There are some common distinctions often made to support this discrimination into two types of change:

Table 1.2 from Teaching Secondary Chemistry (2nd ed) (Taber, 2012b)

However, a little thought suggests that such criteria are not especially useful in supporting the school student making observations, and indeed some of these criteria simply do not stand up to close examination. 2

"the distinction between chemical and physical changes is a rather messy one, with no clear criteria to help students understand the difference"

Taber, 2012b, p.33


So, I was especially interested to know what Tarhan and colleagues had found.

Methodological 'small print'

In reading any study, a consideration of the findings has to be tempered by an understanding of how the data were collected and analysed. Writing-up research reports for journals can be especially challenging as referees and editors may well criticise missing details they feel should be reported, yet often journals impose word-limits on articles.

Currently (2023) this particular journal tells potential authors that "A typical paper for this journal should be between 7000 and 8000 words" which is a little more generous than some other journals. However, Tarhan and colleagues do not fully report all aspects of their study. This may in part be because they need quite a lot of space to describe the experimental teaching scheme (six different jigsaw learning activities).

Whatever the reason:

  • the authors do not provide a copy of the post-test which elicited the responses that were the basis of the identified alternative conceptions; and
  • nor do they explain how the analysis to identify conceptions was undertaken – to show how student responses were classified;
  • similarly, there are no quotations from the interview dialogue to illustrate how the researchers interpreted student comments .

Data analysis is the process of researchers interpreting data so they become evidence for their findings, and generally research journals expect the process to be detailed – but here the reader is simply told,

"Students' understanding of physical and chemical changes was identified according to the post-test and the individual interviews after the process."

Tarhan et al., 2013, p.189

'Misconceptions'

In their paper, Tarhan and colleagues use the term 'misconception' which is often considered a synonym for 'alternative conception'. Commonly, conceptions are referred to as alternative if they are judged to be inconsistent with canonical concepts.

Read about alternative conceptions

Although the term 'misconception' is used 32 times in the paper (not counting instances in the reference list), the term is not explained in the text, presumably because it is assumed that all those working in science education know (and agree) what it means. This is not at all unusual. I once wrote about another study

"[The] qualities of misconceptions are largely assumed by the author and are implicit in what is written…It could be argued that research reports of this type suggest the reported studies may themselves be under-theorised, as rather well-defined technical procedures are used to investigate foci that are themselves only vaguely characterised, and so the technical procedures are themselves largely operationalised without explicit rationale."

Taber, 2013, p.22

Unfortunately, in Tarhan and colleagues' study there are less well-defied technical procedures in relation to how data was analysed to identify 'misconceptions', so leaving the reader with limited grounds for confidence that what are reported are worthy of being described as student conceptions – and are not just errors or guesses made on the test. Our thinking is private, and never available directly to others, and, so, can only be interpreted from the presentations we make to represent our conceptions in a public (shared) space. Sometimes we mis-speak, or we mis-write (so that then our words do not accurately represent our thoughts). Sometimes our intended meanings may be misinterpreted (Taber, 2013).

Perhaps the researchers felt that this process of identifying conceptions from students' texts and utterances was unproblematic – perhaps the assignments seemed so obvious to the researchers that they did not need to exemplify and justify their analytical method. This is unfortunate. There might also be another factor here.

Lost and found in translation?

The study was carried out in Turkey. The paper is in English, and this includes the reported alternative conceptions. The study was carried out "in a public elementary school" (not an international school, for example). Although English is often taught as a foreign language in Turkish schools, the language of instruction, not unreasonably, is Turkish.

So, it seems either

  • the data was collected in (what, for the children, would have been) 'L2' – a second language, or
  • a study carried out (questions asked; answers given) in Turkish has been reported in English, translating where necessary from one language to another.

This issue is not discussed at all in the paper – there is no mention of either the Turkish or English language, nor of anything being translated.

Yet the authors are not oblivious to the significance of language issues in learning. They report how one variant of Jigsaw teaching had "been designed specifically to increase interaction among students of differing language proficiencies in bilingual classrooms" (p.186) and how the research literature reports that sometimes children's ideas reflect "the incorrect use of terms in everyday language" (p.198). However, they did not feel it was necessary to report either that

  1. data had been collected from elementary school children in a second language, or
  2. data had been translated for the purposes of reporting in an English language journal

It seems reasonable to assume they would have appreciated the importance of mentioning option 1, and so it seems much more likely (although readers of the study should not have to guess) the reporting in English involved translation. Yet translation is never a simple algorithmic process, but rather always a matter of interpretation (another stage in analysis), so it would be better if authors always acknowledged this – and offered some basis for readers to consider the translations made were of high quality (Taber, 2018).

Read about guidelines for detailing translation in research reports

It is a general principle that the research community should adopt, surely, that whenever material reported in a research paper has been translated from another language (a) this is reported and (b) evidence of the accuracy and reliability of the translation is offered (Taber, 2018).

I make this point here, as some of the alternative conceptions reported by the authors are a little mystifying, and this may(?) be because their wording has been 'degraded' (and obscured) by imperfect translation.

An alternative conception of combustion?

For example, here are two of the learning objectives from one of the learning activities:

"The students were expected to be able to:

…comment on whether the wood has similar intensive properties before and after combustion

…indicate the combustion reactions in examples of several physical and chemical changes"

Tarhan et al., 2013, p.193

The wording of the first of these examples seems to imply that when wood is burnt, the product is still…wood. That is nonsense, but possibly this is simply a mistranslation of something that made perfect sense in Turkish. (The problem is that a reader can only speculate on whether this is the case, and research reports should be precise and explicit.)

The second learning objective quoted here implies that some combustion reactions are physical changes (or, at least, combustion reactions are components of some physical changes).

Combustion reactions are a class of chemical reactions. 'Chemical reaction' is synonymous with 'chemical change'. So, there are (if you will excuse the double negative) no examples of combustion reactions that are not chemical reactions and which would be said to occur in physical changes. So, this is mystifying, as it is not at all clear what the children were actually being taught unless one assumes the researchers themselves have very serious misconceptions about the chemistry they are teaching.

If a reader actually thought that the researchers themselves held these alternative conceptions

  • the product of combustion of wood is still wood
  • some combustion reactions are (or occur as part of) physical changes

then one could have little confidence in their ability to distinguish between the scientific and alternative conceptions of others. (A reader might also ask how come the journal referees and editor did not ask for corrections here before publication – I certainly wondered about this).

There are other statements the authors make in describing the teaching which are not entirely clear (e.g., "give the order of the changes in matter during combustion reactions", p.194), and this suggests a degree of scepticism is needed in not simply accepting the reported alternative conceptions at face value. This does not negate their interest, but does undermine the paper's authority somewhat.

One of the misconceptions reported in the study is that some students thought that "there is a flame in all combustion reaction". This led me to reflect on whether I could think of any combustion reactions that did not involve a flame – and I must confess none readily came to mind. Perhaps I also have this alternative conception – but it seems a harsh judgement on elementary school learners unless they had actually been taught about combustion reactions without flames (if, indeed, there are such things).

The study reported that some 12 year olds held the 'misconception' that "there is a flame in all combustion reaction[s]".

[Image by Susanne Jutzeler, Schweiz, from Pixabay]

Failing to control variables?

Another objective was for students to "comprehend that temperature has an effect on chemical reaction rate by considering the decay of fruit at room temperature, and the change in color [colour] from green to yellow of fallen leaves in autumn" (p.193). As presented, this is somewhat obscure.

Presumably it is not meant to be a comparison between:

the rate of
decay of fruit at room temperature		andthe rate of
change in colour of fallen leaves in autumn
Explaining that temperature has an effect on chemical reaction rate?

Clearly, even if the change of colour of leaves takes place at a different temperature to room temperature, one cannot compare between totally different processes at different temperatures and draw any conclusions about how "temperature has an effect on chemical reaction rate" . (Presumably, 'control of variables' is taught in the Turkish science curriculum.)

So, one assumes these are two different examples…

But that does not help matters too much. The "decay of fruit at room temperature" (nor, indeed, any other process studied at a single temperature) cannot offer any indication of how "temperature has an effect on chemical reaction rate". The change of colours in leaves of deciduous trees (that usually begins before they fall) is triggered by environmental conditions such as change in day length and temperature. This is part of a very complex system involving a range of pigments, whilst water content of the leaf decreases (once the supply of water through the tree's vascular system is cut off), and it is not clear how much detail these twelve year olds were taught…but it is certainly not a simple matter of a reaction changing rate according to temperature.

Evaluating conceptions

Tarhan and colleagues report their identified alternative conceptions ('misconceptions') under a series of headings. These are reported in their table 4 (p.195). A reader certainly finds some of the entries in this table easy to interpret: they clearly seem to reflect ideas contrary to the canonical science one would expect to be reflected in the curriculum and teaching. Other statements are less obviously evidence of alternative conceptions as they do not immediately seem necessarily at odds with scientific accounts (e.g., associating combustion reactions with flames).

Other reported misconceptions are harder to evaluate. School science is in effect a set of models and representations of scientific accounts that often simplify the actual current state of scientific knowledge. Unless we know exactly what has been taught it is not entirely clear if students' ideas are credit-worthy or erroneous in the specific context of their curriculum.

Moreover, as the paper does not report the data and its analysis, but simply the outcome of the analysis, readers do not know on what basis judgements have been made to assign learners as having one of the listed misconceptions.


Changes of state are chemical changes

A few students from the lecture-based teaching condition were identified as 'having' the misconception that 'changes of state are chemical changes'. This seems a pretty serious error at the end of a teaching sequence on chemical and physical changes.

However, this raises a common issue in terms of reports of alternative conceptions – what exactly does it mean to say that a student has a conception that 'changes of state are chemical changes'? A conception is a feature of someone's thinking – but that encompasses a vast range of potential possibilities from a fleeting notion that is soon forgotten ('I wonder if s orbitals are so-called because they are spherical?') to an on-going commitment to an extensive framework of ideas that a life is lived by (Buddhism, Roman Catholicism, Liberalism, Hedonism, Marxism…).

A person's conceptions can vary along a range of characteristics (Figure from Taber, 2014)

The statement that 'Changes of state are chemical changes' is unlikely to be the basis of anyone's personal creed. It could simply be a confusion of terms. Perhaps a student had a decent understanding of the essential distinction between chemical and physical changes but got the terms mixed up (or was thinking that 'changes of state' meant 'chemical reaction'). That is certainty a serious error that needs correcting, but in terms of understanding of the science, would seem to be less worrying than a deeper conceptual problem.

In their commentary, the authors note of these children:

"They thought that if ice was heated up water formed, and if water was heated steam formed, so new matter was formed and chemical changes occurred".

Tarhan et al., 2013, p.197

It is not clear if this was an explanation the learners gave for thinking "changes of state are chemical changes", or whether "changes of state are chemical changes" was the researchers' gloss on children commenting that "if ice was heated up water formed, and if water was heated steam formed, so new matter was formed and chemical changes occurred".

That a range of students are said to have precisely the same train of thought leads a reader (or, at least, certainly one with experience of undertaking research of this kind) to ask if these are open-ended responses produced by the children, or the selection by the children of one of a number of options offered by the researchers (as pointed out above, the data analysis is not discussed in detail in the paper). That makes a difference in how much weight we might give to the prevalence of the response (putting a tick by the most likely looking option requires less commitment to, and appreciation of, an idea than setting it out yourself in your own personally composed text), illustrating why it is important that research journals should require researchers to give full accounts of their instrumentation and analysis.

Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change

Thirteen of the children (all in the lecture-based teaching condition) were considered to have the conception "Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change". This is clearly a much more specific conception (than 'changes of state are chemical changes') which can be analysed into three components:

  • a change of state is a chemical change, AND
  • we know this because such changes involve a change in identity, AND
  • we know that because a change of state leads to a change in density

Terhan and colleagues claim this conception was "first determined in this study" (p.195).

The specificity is intriguing here – if so many students explicitly and individually built this argument for themselves then this is an especially interesting finding. Unfortunately, the paper does not give enough detail of the methodology for a reader to know if this was the case. Again, if students were just agreeing with an argument offered as an option on the assessment instrument then it is of note, but less significant (as in such cases students might agree with the statement simply because one component resonated – or they may even be guessing rather than leaving an item unanswered). Again this does not completely negate the finding, but it leaves its status very unclear.

Taken together these first two claimed results seem inconsistent – as at least 13 students seem to think "Changes of state are chemical changes". That is, all those who thought that "Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change" would seem to have thought that "Changes of state are chemical changes" (see the Venn diagram below). Yet, we are also told that only five students held the less specific and seemingly subsuming conception "changes of state are chemical changes".

If 13 students think that changes of state are chemical changes because a change of density implies a change of identity; what does it mean that only 5 students think that changes of state are chemical changes?

This looks like an error, but perhaps is just a lack of sufficient detail to make the findings clear. Alternatively, perhaps this indicates some failure in translating material accurately into English.

The changes in the pure matters are physical changes

Six children in the lecture-based teaching condition and one in the jigsaw learning condition were reported as holding the conception that "The changes in the pure matters are physical changes". The authors do not explain what they mean here by "pure matters" (sic, presumably 'matter'?). The only place this term is used in the paper is in relation to this conception (p.195, p.197).

The only other reference to 'pure' was in one of the learning objectives for the teaching:

  • explain the changes of state of water depending on temperature and pressure; give various examples for other pure substances (p.191)

If "pure matter" means a pure sample of a substance, then changes in pure substances are all physical – by definition a chemical changes leads to a different substance/different substances. That would explain why this conception was "first determined [as a misconception] in this study", p.195, as it is not actually a misconception)". So, it does not seem clear precisely why the researchers feel these children have got something wrong here. Again, perhaps this is a failure of translation rather than a failure in the original study?

Changes in shape?

Tarhan and colleagues report two conceptions under the subheading of 'changes in shape'. They seem to be thinking here more of grain size than shape as such. (Another translation issue?) One reported misconception is that if cube sugar is granulated, sugar particles become small [smaller?].

Is it really a misconception to think that "If cube sugar is granulated, sugar particles become small"?

(Image by Bruno /Germany from Pixabay)

Tarhan and colleagues reported that two children in the experimental condition, and 13 in the control condition thought that "If cube sugar is granulated, sugar particles become small". Sugar cubes are made of granules of sugar weakly joined together – they can easily be crumbled into the separate grains. The grains are clearly smaller than the cubes. So, what is important here is what is meant/understood* by the children by the term 'particles'.

(* If this phrasing was produced by the children, then we want to know what they meant by it. If, however, the children were agreeing with a phrase presented to them by researchers, then we wish to know how they understood it.)

If this means quanticle level particles, molecules, then it is clearly an alternative conception – each grain contain vast numbers of molecules, and the molecules are unchanged by the breaking up the cubes. If, however, particles here refers to the cube and grains**, then it is a fair reflection of what happens: one quite large particle of sugar is broken up into many much smaller particles. The ambiguity of the (English) word 'particles' in such contexts is well recognised.

(** That is, if the children used the word 'particles' – did they mean the cubes/grains as particles of sugar? If however the phrasing was produced by the researchers and presented to the children, and if the researchers meant 'particles' to mean 'molecules'; did the children appreciate that intention, or did they understand 'particles' to refer to the cubes and grains?)

However, as no detail is given on the actual data collected (e.g., is this the children's own words; was this based on an open response?), and how it was analysed (and, as I suspect this all occurred in Turkish) the reader has no way to check on this interpretation of the data.

What kind of change is dissolving?

Tarhan and colleagues report a number of 'misconceptions' under the heading of 'molecular solubility'. Two of these are:

  • "The solvation processes are always chemical changes"
  • "The solvation processes are always physical changes"

This reflects a problem of teaching about physical and chemical changes. Dissolving is normally seen as a physical change: there is no new chemical substance formed and dissolving is usually fairly readily reversed. However, as bonds are broken and formed it also has some resemblance to chemical change.2

In dissolving common salt in water, strong ionic bonds are disrupted and the ions are strongly solvated. Yet the usual convention is still to consider this a physical change – the original substance, the salt, can be readily recovered by evaporation of the solvent. A solution is considered a kind of mixture. In any case, as Tarhan and colleagues refer to 'molecular' solubility (strictly solubility refers to substances, not molecules, but still) they were, presumably, only dealing with examples of the dissolving of substances with discrete molecules.

Taking together these two conceptions, it seems that Tarhan and colleagues think that dissolving is sometimes a physical change, and sometimes a chemical change. Presumably they have some criterion or criteria to distinguish those examples of dissolving they consider physical changes from those they consider chemical changes. A reader can only speculate how a learner observing some solute dissolve in a solvent is expected to distinguish these cases. The researchers do not explain what was taught to the students, so it is difficult to appreciate quite what the students supposedly got wrong here.

Sugar is invisible in the water, because new matter is formed

The idea that learners think that new matter is formed on dissolving would indeed be an alternative conception. The canonical view is that new matter is only formed in very high energy processes – such as in the big bang. In both chemical and physical processes studied in the school laboratory there may be transformations of matter, but no new matter.

This seems a rather extreme 'misconception' for the learners to hold. However, a reader might wonder if the students actually suggested that a new substance was formed, and this has been mistranslated. (The Turkish word 'madde' seems to mean either matter or substance.) If these students thought that a new type of substance was formed then this would be an alternative conception (and it would be interesting to know why this led to sugar being invisible – unless they were simply arguing that different appearance implied different substance).

While sugar is dissolving in the water, water damages the structure of sugar and sugar splits off

Whether this is a genuine alternative conception or just imprecise use of language is not clear. It seems reasonable to suggest that while sugar is dissolving in the water, the process breaks up the structure of solid sugar and sugar molecules split off – so some more detail would be useful here. Again, if there has been translation from Turkish this may have lost some of the nuance of the original phrasing through translation into English.

The phrasing reflects an alternative conception that in chemical reactions one reactant is an active agent (here the water doing the damaging) and the other the patient, that is passive and acted upon (here the sugar being damaged) – rather than seeing the reaction as an interaction between two species (Taber & García Franco, 2010) – but there is no suggestion in their paper that this is the issue Tarhan and colleagues are highlighting here.

When sugar dissolves in water, it reacts with water and disappears from sight

If the children thought that dissolving was a chemical reaction then this is an alternative conception – the sugar does indeed disappear from sight, but there has been no reaction.

Again, we might ask if this was actually a misunderstanding (misconception), or imprecise use of language. The sugar does 'react' with the water in the everyday sense of 'reaction'. But this is not a chemical reaction, so this terminology should be avoided in this context.

Even in science, 'reaction' means something different in chemistry and physics: in the sense of Newtonian physics, during dissolving, when a water molecule attracts a sugar molecule {'action')'} there will be an equal and oppositely directed reaction as the sugar molecule attracts the water molecule. This is Newton's third law, which applies to quanticles as much as to planets. If a water molecule and a sugar molecule collide, the force applied by the sugar molecule on the water molecule is equal to the force applied by the water molecule on the sugar molecule.

Read about learning difficulties with Newton's third law

So, 'sugar reacts with water' could be

  • a misunderstanding of dissolving (a genuine alternative conception);
  • a misuse of the chemical term 'reaction'; or
  • a use of the everyday term 'reaction' in a context where this should be avoided as it can be misunderstood

These are somewhat different problems for a teacher to address.

Molecules split off in physical changes and atoms split off in chemical changes

Ten of the children are said to have demonstrated the 'misconception' that molecules split off in physical changes and atoms split off in chemical changes. The authors claim that this misconception has not been reported in previous studies. But is this really a misconception? It may be a simplistic, and imprecise, statement – but I think when I was teaching youngsters of this age I would have been happy to find they have this notion – which at least seems to reflect an ability to imagine and visualise processes at the molecular level.

In dissolving or melting/boiling of simple molecular substances, molecules do indeed 'split off' in a sense, and in at least some chemical changes we can posit mechanisms that, in simple terms at least, involve atoms 'splitting off' from molecules.

So, again, this is another example of how this study is tantalising, without being very informative. The reader is not clear in what sense this is viewed as wrong, or how the conception was detected. (Again, for ten different students to specifically think that 'molecules split off in physical changes and atoms split off in chemical changes' makes one wonder if they volunteered this, or have simply agreed with the statement when having it presented to them).

In conclusion

The main thrust of Tarhan and colleagues' study was to report on an innovation using jig-saw learning (which unfortunately compared this with a form of pedagogy widely considered unsuitable for young children, so offering a limited basis for judging effectiveness of the innovation). As part of the study they collected data to evaluate learning in the two conditions, and used this to identify misconceptions students demonstrated after being taught about physical and chemical changes. The researchers provide a long list of identified misconceptions – but it is not always obvious why these are considered misconceptions, and what the desired responses matching teaching models were.

The researchers do not detail their data collection and analysis instruments and protocols in sufficient detail for a readers to appreciate what they mean by their results. In particular, what it means to have a misconception – e.g., to give a definitive statement in an interview, or just to select some response on a test as the answer that looked most promising at the time. Clearly we give much more weight to a notion that a learner presents in their own words as an explanation for some phenomenon, than the selection of one option from a menu of statements presented to them that comes with no indication of their confidence in the selection made.

Of particular concern: either the children were asked questions in a second language that they may not have been sufficiently fluent in to fully understand questions or compose clear responses; or none of the misconceptions reported are presented in their original form and they have all been translated by someone (unspecified) of uncertain ability as a translator. (A suitably qualified translator would need to have high competence in both languages and a strong familiarity with the subject matter being translated.)

In the circumstances, Tarhan and colleagues' reported misconceptions are little more than intriguing. In science, the outcome of a study is only informative in the context of understanding exactly how the data were obtained, and how they have been processed. Without that, readers are asked to take a researcher's conclusions on faith, rather than be persuaded of them by a logical chain of argument.

p.s. For anyone who did not know, but wondered: s orbitals are not so-called because they are spherical: the designation derives from a label ('sharp') that was applied to some lines in atomic spectra.

Work cited
Notes

1 To my reading, the publication title 'Research in Science and Technological Education' seems to suggest the journal has two distinct and somewhat disconnected foci, that is:

Research in ( Science ) and ( Technological Education )

And it would be better (that is, most consistently) titled as

Research in Science and Technology Education

{Research in ( Science and Technology ) Education}

or

Research in Scientific and Technological Education

{Research in ( Scientific and Technological ) Education}

but, hey, I know I am pedantic.

2 The table (Table 1.2 in the source) was followed by the following text:

"The first criterion listed is the most fundamental and is generally clear cut as long as the substances present before and after the change are known. If a new substance has been produced, it will almost certainly have different melting and boiling temperatures than the original substance.

The other [criteria] are much more dubious. Some chemical changes involve a great deal of energy being released, such as the example of burning magnesium in air, or even require a considerable energy input, such as the example of the electrolysis of water. However, other reactions may not obviously involve large energy transfers, for example when the enthalpy and entropy changes more or less cancel each other out…. The rusting of iron is a chemical reaction, but usually occurs so slowly that it is not apparent whether the process involves much energy transfer ….

Generally speaking, physical changes are more readily reversible than chemical changes. However, again this is not a very definitive criterion. The idea that chemical reactions tend to either 'go' or not is a useful approximation, but there are many examples of reactions that can be readily reversed…. In principle, all reactions involve equilibria of forward and reverse reactions, and can be reversed by changing the conditions sufficiently. When hydrogen and oxygen are exploded, it takes a pedant to claim that there is also a process of water molecules being converted into oxygen and hydrogen molecules as the reaction proceeds, which means the reaction will continue for ever. Technically such a claim may be true, but for all practical purposes the explosion reflects a reaction that very quickly goes to completion.

One technique that can be used to separate iodine from sand is to warm the mixture gently in an evaporating basin, over which is placed an upturned beaker or funnel. The iodine will sublime – turn to vapour – before recondensing on the cold glass, separated from the sand. The same technique may be used if ammonium chloride is mixed with the sand. In both cases the separation is achieved because sand (which has a high melting temperature) is mixed with another substance in the solid state that is readily changed into a vapour by warming, and then readily recovered as a solid sample when the vapour is in contact with a colder surface. There are then reversible changes involved in both cases:

solid iodine ➝ iodine vapour

ammonium chloride ➝ ammonia + hydrogen chloride

In the first case, the process involves only changes of state: evaporation and condensation – collectively called sublimation. However the second case involves one substance (a salt) changing to two other substances. To a student seeing these changes demonstrated, there would be little basis to infer one is (usually considered as) a chemical change, but not the other. …

The final criterion in Table 1.2 concerns whether bonds are broken and made during a change, and this can only be meaningful for students once they have learnt about particle models of the submicroscopic structure of matter… In a chemical change, there will be the breaking of bonds that hold together the reactants and the formation of new bonds in the products. However, we have to be careful here what we mean by 'bond' …

When ice melts and water boils, 'intermolecular' forces between molecules are disrupted and this includes the breaking of hydrogen 'bonds'. However, when people talk about bond breaking in the context of chemical and physical changes, they tend to mean strong chemical bonds such as covalent, ionic and metallic bonds…

Yet even this is not clear cut. When metals evaporate or are boiled, metallic bonds are broken, although the vapour is not normally considered a different substance. When elements such as carbon and phosphorus undergo phase changes relating to allotropy, there is breaking, and forming, of bonds, which might suggest these changes are chemical and that the different forms of the same elements should be considered different substances. …

A particularly tricky case occurs when we dissolve materials to form solutions, especially materials with ionic bonding…. Dissolving tends to involve small energy changes, and to be readily reversible, and is generally considered a physical change. However, to dissolve an ionic compound such as sodium chloride (table salt), the strong ionic bonds between the sodium and chloride ions have to be overcome (and new bonds must form between the ions and solvent molecules). This would seem to suggest that dissolving can be a chemical change according to the criterion of bond breaking and formation (Table 1.2)."

(Taber, 2012b, pp.31-33)