Category: analogy

That's my theory…and I am sticking to it

Keith S. Taber

It is something of a cliché, so it was not the phrase itself ("…that's my theory anyway and I'm sticking to it") that caught my attention, but that I heard it used by a scientist.

The duvet cover mystery

Dr Penny Sarchet, Managing Editor of New Scientist was talking on an episode ('Answers to Your Science Questions') of BBC Inside Science, where a panel were presented with listener's questions.

screenshot pf [art of webpage showing inside science icon
Answers to Your Science Questions?

Dr Sarchet was responding the query:

why, when I put a duvet cover in the washing machine with other items, they all end up inside the duvet cover when the programme finishes

Now this is a phenomenon I have observed myself, and I was not sure of the explanation. As it happened, Dr Sarchet had also wondered about this, indeed she had apparently "thought about this on a weekly basis for as long as I can remember", and had a – well let me say for the moment – suggestion.

The suggestion was that

"what might be going on here is, obviously when you've got a duvet cover and if you have not sort of buttoned it up before putting it in the wash, you've got a very wide opening, so that's easy statistically for things to enter it, and then as it twists around in the wash, it's actually harder to leave. So, what you've got is kind of a difficulty gradient, things are more likely to go in than they are to come out; and my reckoning is if that keeps happening for a long enough period, enough cycles, eventually everything ends up inside."

Now, I tried to visualise this, and was not convinced. In my mental simulation, the configuration of the duvet cover is such that:

  • initially, ingress and egress are both readily possible; then,
  • as twisting begins, possible but less readily; then,
  • when the duvet becomes very twisted, both ingress and egress are blocked.

There seems to be a 'difficulty gradient' over time, but in my mind this seemed symmetrical in relation to the direction of passage – moving in and out of the duvet cover. Perhaps some items will enter the duvet before the passage is closed – but why should this be all of them, if items can leave as well as enter up to that point?

I am not sure I am right here because I might just be lacking sufficient creative simulation capacity (imagination), or I may not have fully appreciated the mechanism being suggested. After all, a communicator has a meaning in mind, but the text produced (what they say or write, etc.) only represents that meaning and does not inherently contain it. It is up to the audience to make good sense of it. Perhaps I failed. After all, the phenomenon seems to be a real one, so something is going on.

Woman contemplating washing has an idea
An insight (Image of woman with washing by Amine Tadri, Image of lamp by GraphicsSC from Pixabay)

Analogy in scientific discovery

But what intrigued me about the suggestion was less its veracity, but rather two features of how it was presented. As my heading suggests, Dr Sarchet closed here proposal with the statement that "that's my theory anyway and I'm sticking to it". She prefaced her proposal by reporting on its origin:

"I'd like to argue this might be a little bit like cell biology…"

Dr Sarchet is a biologist, with her doctorate in development genetics, and I thought it was interesting that she was making sense of washing dynamics in terms of cells. Interesting, but not strange: we all seek to make sense of things, and to do so we draw on the range of interpretive resources we have available – the knowledge and understanding, language, images, experiences, and so forth that we carry around represented in our heads. That a biologist might derive a suggestion from a biological source therefore seems quite natural.

Moreover, the process operating is one that is common in science itself. The process I refer to is that of analogy,

"the reason I kind of try to claim that's like cell biology is sometimes, certain substance, it is much easier for them to get into the cell, through the cell membrane because of the way it is made than it is for them to randomly diffuse out again. And that's a really sort of clever, not kind of actively driven way, of creating order"

I have written a lot about analogy on this site, but mostly in relation to science teaching and science communication more widely. That is, how teachers 'make the unfamiliar familiar' by suggesting that some abstract notion to be learnt is actually, in some way, just like something the learners are already familiar and quite comfortable with – it is like a ladder, or the high jump, or the way people arrange themselves sitting on a bus, or like water passing through a drain hole, or whatever.

However analogy is also actually used within scientific practice itself, in the discovery process. Perhaps we should not be surprised then that analogies are often found when scientists talk or write about their work, as well as commonly being used by journalists and authors of popular science books.

Read about analogy in science

Read examples of scientific analogies

Sometimes the use of analogy within science itself may be making such small jumps that we may not notice analogy is being used:

Element X is in the same group of the periodic table as element Y, and element Y forms a compound with element A with the properties I am interested in, so I wonder if element X also forms a compound with element A with those properties?

Sometimes however, the jumps are across topics or even sciences.

Does this strange new property of the atomic nucleus suggest the nucleus can behave a bit like a drop of liquid; and, if so, can ideas from the physics of fluids be useful in this different area of nuclear physics?

In this way, the recognition of a potential analogy suggests conjectures that can be tested. Use of such analogies is therefore part of the creative aspect of science.

Perhaps the ultimate use of analogy occurs in physics where equations are found to transfer from one context to another with the right substitutions (e.g., 'it's a wave phenomenon, so we can apply this set of equations that work for all wave phenomena'). As learners will find if they continue with physics as an elective school subject:

We have an equation for the flow of charge in an electrical conductor, and fluid flows, so the same basic equation could work there. And we talk of heat flow, so we should be able to adopt the same basic equation…

I once designed a teaching activity for upper secondary learners (Taber, 2011a) based about the ways certain phenomena are analogous in the sense of following exponential decays (e.g., capacity discharge, radioactive decay, cooling…). For learners not yet introduced to the exponential decay equation this analogy can be built upon the common feature of a negative feedback loop where the magnitude of a driver (excess temperature, radioactive material, p.d.) is reduced by the effect it drives (heat, radioactivity, current);

An exponential decay occurs when a negative feedback loop operates.

In capacitor discharge, A could be p.d. across capacitor, and B current (+ indicates the more p.d. across the plates, the more current flows; – indicates the more current flows {removing charge from the plates}, the lower the p.d. across the plates).

As p.d. falls, the current falls (and so the rate of drop of charge across plates fall) and so the rate of p.d. dropping also falls. …

Similar arguments apply to radioactivity and amount of radioactive material; and cooling and excess temperature.

Read about the activity: Identifying patterns in science

Progress in science relies on empirical studies to test ideas: but empirical tests can only be carried out after an act of creative imagination has produced a hypothesis to test. Because science is rightly seen as rational and logical, we can easily lose sight of the creative aspect:

"Creativity is certainly a central part of science, and indeed part of the expectation of the major qualification for any researcher, the Ph.D. degree, is that work should be original. Originality in this context, means offering something that is new to the literature in the field concerned. The originality may be of various kinds: applying existing ideas in a novel context; developing new instrumentation or analytical techniques; offering a new synthesis of disparate literature and so forth. However, the key is there needs to be some novelty. Arthur Koestler argued that science, art, and humour, all relied on the same creative processes of bringing together previously unrelated ideas into a new juxtaposition."

Taber, 2011b

Science teaching needs to reflect how science is creative and so open to speculative divergent thought (as well as being logical and needing disciplined convergent thinking!)

"Science teachers need to celebrate the creative aspects of science – the context of discovery. They should emphasise

  • how scientific models are thinking tools created by scientists for exploring our understanding of phenomena;
  • how teaching models are speculative attempts to 'make the unfamiliar familiar' by suggesting that 'in some ways it's a bit like something you already know about'; and in particular
  • how scientists always have to trust imagination as a source of ideas that may lead to discovery.

However, it is equally important that the creative act is always tempered by critical reflection. Scientific models have limitations; teaching models and analogies may be misleading; and all of us have to select carefully from among the many imaginative possibilities we can generate if we seek ideas that help us understand rather than just fantasise."

Taber, 2011b
That's not your theory!

But the other point I noted, which I raised at the beginning of this piece, was how Dr Sarchet signed off "…that's my theory anyway and I'm sticking to it" which from a scientific perspective seemed problematic at two levels.

I am not being critical of Dr Sarchet as she was just using a chiché in a humorous vein, and I am sure was not expecting to be taken seriously. Other scientists listening to the programme will have surely realised that. I am not so sure if lay people, or school age learners, will have picked up on the humour though.

As a scientist, Dr Sarchet would, I am sure, acknowledge the provisional nature of scientific knowledge: all our theories are open to being replaced if new evidence or new ways of understanding the evidence suggest they are inadequate. Scientists, being human, do get attached to their 'pet' theories, but a good scientist should be prepared to give up an idea and move on when this is indicated. Scientists should not 'stick to' a theory come what may. Just as well, or we would still be operating with phlogiston, caloric and the aether.

Read about historical scientific conceptions

But in any case, I am not convinced that Dr Sarchet had a theory here. A theory is more than an isolated idea – a theory is usually more extensive, a framework connecting related concepts, perhaps encompassing one or more empirical generalisations (laws), and being supported by a body of evidence.

What Dr Sarchet had was a conjecture or hypothesis that she had not yet tested. Certainly having a testable hypothesis is an important starting point for developing a theory – but it is not sufficient.

The hypothesis of continental drift was proposed decades before sufficient investigations and evidence led to the modern theory of tectonics. This is the general situation: the hypothesis or conjecture is a critical step, but by itself does not lead to new knowledge.

Common conceptions of scientific theories

I do not imagine Dr Sarchet really considered her suggestion had reached theory status either. Again, she was just using a common expression. But this is just one example of how words that have precise technical meanings in science (element, energy, force, momentum, plant, substance…) are used with more flexible and fluid meanings in everyday life.

For most people, a 'theory' (let me denote this theorylifeworld to mean how the word is used in everyday discourse) is nothing special – we all have theorieslifeworld all the time. Perhaps a theorylifeworld that a particular football team will win on Saturday, or that next door's cat hates you, or that they are putting less biscuits in these packets than they used to. A theorylifeworld can be produced with little effort, held with various degrees of commitment (often quickly forgotten when experience does not fit, but sometimes 'stuck to' regardless!) and often abandoned with little cost.

Now scientific theories are not like that. In one curriculum context, theoriesscience were defined as 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world'. But, if learners come to class having long heard and used the term 'theory' with its 'lifeworld' (that is, everyday, informal) meaning then they think they already know what a theory is (and it is not a consistent, comprehensive, coherent and extensively evidenced source of explanations of aspects of the natural world!)

This is not just speculation, as studies have asked school age learners how they understand such terms. One study, undertaken in that curriculum context that suggested theories are 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world' found most respondents had quite a different idea (Taber, et al., 2015). They generally saw a theory as something a scientist made up effortlessly (almost on a whim). Accordingly, they did not think that theories had a very high status – as they had not yet been tested in any way. Once tested, any 'theory' that passed the test ceased to be a theory – perhaps becoming a law: something seen as proven and having (unlike the theory) high epistemological status.

This common pattern is caricatured in the figure:

Student understandings of scientific epistemology were generally simplistic. For most interviewees theories were just ideas, until they were proved to be correct.
From Taber et al., 2015

So, laws were seen as of higher status than theories. Laws were proven and so not open to questioning (that is, their conjectural nature as generalisations that could never be proven were not recognised), whereas theories were little more than the romanced flotsam and jetsam of someone's imagination.

It is just a theory

Now of course, I am generalising here from a small sample (of 13-14 year olds learners from a few schools in one country) and individual learners have their own nuanced understandings – aligned to the curriculum account to different degrees.

One interviewed learner confused theories with theorems from mathematics . But, as a generalisation, the learners interviewed tended to see a theory much more as a hypotheses or conjecture than as a worked through conceptual framework of related ideas that are usually supported by a range of evidence, often collected by deliberate testing.

This is useful for the teacher to bear in mind as clearly when the teacher refers to theory, the learners will often understand this as something quite different from what was intended. Probably the only response to this is to review the intended meaning of 'scientific theory' each time one is discussed. Learners can overcome their alternative conceptions with sufficient support and engagement, but the teacher has to work hard when the existing idea is not only long-established but also being reinforced by everyday discourse (and scientists in the media such as Dr Sarchet shifting to the vernacular, as non-scientists may not recognise the transition from a technical to an everyday code).

So, for example , the theory of natural selection (or general relativity if you prefer), is not proven because in science we can never prove general ideas, and so it is just a theory. But theories are all we are ever going to get in science (for certainties look elsewhere), and some of them are so well tested and supported that in practice we treat them as secure and almost as if certain knowledge.

Perhaps it does not matter enormously if many learners leave school thinking general relativity is only a theorylifeworld. Perhaps it does not even matter that much for many learners if they leave school thinking natural selection is only a theorylifeworld. But when people dismiss climate change or the basis of vaccination as 'just a theory' this is much more problematic, as it invites an attitude that these 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world' are of no more merit than your neighbour's 'theory' about the next set of winning lottery numbers or a politician's 'theory' about the merits of high import tariffs for reducing the price of eggs. And that is a problem, as climate change and vaccination really matter – critical to individual and collective survival.

At least, that's my theory, and I'm sticking to it.

Work cited:

The book  Student Thinking and Learning in Science: Perspectives on the Nature and Development of Learners' Ideas gives an account of the nature of learners' conceptions, and how they develop, and how teachers can plan teaching accordingly.

It includes many examples of student alternative conceptions in science topics.

Cells are buzzing cities that are balloons with harpoons

What can either wander door to door, or rush to respond; and when it arrives might touch, sniff, nip, rear up, stroke, seal, or kill?

Keith S. Taber

a science teacher would need to be more circumspect in throwing some of these metaphors out there, without then doing some work to transition from them to more technical, literal, and canonical accounts

BBC Radio 4's 'Start the week' programme is not a science programme, but tends to invite in guests (often authors of some kind) each week according to some common theme. This week there was a science theme and the episode was titled 'Building the Body, Opening the Heart', and was fascinating. It also offers something of a case study in how science gets communicated in the media.

Building the Body, Opening the Heart

The guests all had life-science backgrounds:

Their host was geneticist and broadcaster Adam Rutherford.

Communicating science through the media

As a science educator I listen to science programmes both to enhance and update my own science knowledge and understanding, but also to hear how experts present scientific ideas when communicating to a general audience. Although neither science popularisation nor the work of scientists in communicating to the public is entirely the same as formal teaching (for example,

  • there is no curriculum with specified target knowledge; and
  • the audiences
    • are not well-defined,
    • are usually much more diverse than found in classrooms, and
    • are free to leave at any point they lose interest or get a better offer),

they are, like teachers, seeking to inform and explain science.

Science communicators, whether professional journalists or scientists popularising their work, face similar challenges to science teachers in getting across often complex and abstract ideas; and, like them, need to make the unfamiliar familiar. Science teachers are taught about how they need to connect new material with the learners' prior knowledge and experiences if it is to make sense to the students. But successful broadcasters and popularisers also know they need to do this, using such tactics as simplification, modelling, metaphor and simile, analogy, teleology, anthropomorphism and narrative.

Perhaps one of the the biggest differences between science teaching and science communication in the media is the ultimate criterion of success. For science teachers this is (sadly) usually, primarily at least, whether students have understood the material, and will later recall it, sufficiently to demonstrate target knowledge in exams. The teacher may prefer to focus on whether students enjoy science, or develop good attitudes to science, or will consider working in science: but, even so, they are usually held to account for students' performance levels in high-stakes tests.

Science journalists and popularisers do not need to worry about that. Rather, they have to be sufficiently engaging for the audience to feel they are learning something of interest and understanding it. Of course, teachers certainly need to be engaging as well, but they cannot compromise what is taught, and how it is understood, in order to entertain.

With that in mind, I was fascinated at the range of ways the panel of guests communicated the science in this radio show. Much of the programme had a focus on cells – and these were described in a variety of ways.

Talking about cells

Dr Rutherford introduced cells as

  • "the basic building blocks of life on earth"; and observed that he had
  • "spent much of my life staring down microscopes at these funny, sort of mundane, unremarkable, gloopy balloons"; before suggesting that cells were
  • "actually really these incredible cities buzzing with activity".

Dr. Mukherjee noted that

"they're fantastical living machines" [where a cell is the] "smallest unit of life…and these units were built, as it were, part upon part like you would build a Lego kit"

Listeners were told how Robert Hooke named 'cells' after observing cork under the microscope because the material looked like a series of small rooms (like the cells where monks slept in monasteries). Hooke (1665) reported,

"I took a good clear piece of Cork, and with a Pen-knife sharpen'd as keen as a Razor, I cut a piece of it off, and…cut off from the former smooth surface an exceeding thin piece of it, and…I could exceeding plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular; yet it was not unlike a Honey-comb in these particulars

…these pores, or cells, were not very deep, but consisted of a great many little Boxes, separated out of one continued long pore, by certain Diaphragms, as is visible by the Figure B, which represents a sight of those pores split the long-ways.

Robert Hooke
Hooke's drawing of the 'pores' or 'cells' in cork

Components of cells

Dr. Mukherjee described how

"In my book I sort of board the cell as though it's a spacecraft, you will see that it's in fact organised into rooms and there are byways and channels and of course all of these organelles which allow it to work."

We were told that "the cell has its own skeleton", and that the organelles included the mitochondria and nuclei ,

"[mitochondria] are the energy producing organelles, they make energy in most cells, our cells for instance, in human cells. In human cells there's a nucleus, which stores DNA, which is where all the genetic information is stored."

A cell that secretes antibodies which are like harpoons or missiles that it sends out to kill a pathogen?

(Images by by envandrare and OpenClipart-Vectors from Pixabay)

Immune cells

Rutherford moved the conversation onto the immune system, prompting 'Sid' that "There's a lovely phrase you use to describe T cells, which is door to door wanderers that can detect even the whiff of an invader". Dr. Mukherjee distinguished between the cells of the innate immune system,

"Those are usually the first responder cells. In humans they would be macrophages, and neutrophils and monocytes among them. These cells usually rush to the site of an injury, or an infection, and they try to kill the pathogen, or seal up the pathogen…"

and the cells of the adaptive system, such as B cells and T cells,

"The B cell is a cell that eventually becomes a plasma cell which secretes antibodies. Antibodies, they are like harpoons or missiles which the cell sends out to kill a pathogen…

[A T cell] goes around sniffing other cells, basically touching them and trying to find out whether they have been altered in some way, particularly if they are carrying inside them a virus or any other kind of pathogen, and if it finds this pathogen or a virus in your body, it is going to go and kill that virus or pathogen"

A cell that goes around sniffing other cells, touching them? 1
(Images by allinonemovie and OpenClipart-Vectors from Pixabay)

Cells of the heart

Another topic was the work of Professor Harding on the heart. She informed listeners that heart cells did not get replaced very quickly, so that typically when a person dies half of their heart cells had been there since birth! (That was something I had not realised. It is believed that this is related to how heart cells need to pulse in synchrony so that the whole organ functions as an effective pumping device – making long lasting cells that seldom need replacing more important than in many other tissues.)

At least, this relates to the cardiomyocytes – the cells that pulse when the heart beats (a pulse that can now be observed in single cells in vitro). Professor Harding described how in the heart tissue there are also other 'supporting' cells, such as "resident macrophages" (immune cells) as well as other cells moving around the cardiomyocytes. She describe her observations of the cells in Petri dishes,

"When you look at them in the dish it's incredible to see them interact. I've got a… video [of] cardiomyocytes in a dish. The cardiomyocytes pretty much just stay there and beat and don't do anything very much, and I had this on time lapse, and you could see cells moving around them. And so, in one case, the cell (I think it was a fibroblast, it looked like a fibroblast), it came and it palpated at the cardiomyocyte, and it nipped off bits of it, it sampled bits of the cardiomyocyte, and it just stroked it all the way round, and then it was, it seemed to like it a lot.

[In] another dish I had the same sort of cardiomyocyte, a very similar cell came in, it went up to the cardiomyocyte, it touched it, and as soon as it touched it, I can only describe it as it reared up and it had, little blobs appeared all over its surface, and it rushed off, literally rushed off, although it was time lapse so it was two minutes over 24 hours, so, it literally rushed off, so what had it found, why did one like it and the other one didn't?"

Making the unfamiliar, familiar

The snippets from the broadcast that I have reported above demonstrate a wide range of ways that the unfamiliar is made familiar by describing it in terms that a listener can relate to through their existing prior knowledge and experience. In these various examples the listener is left to carry across from the analogue features of the familiar (the city, the Lego bricks, human interactions, etc.) those that parallel features of the target concept – the cell. So, for example, the listener is assumed to appreciate that cells, unlike Lego bricks, are not built up through rigid, raised lumps that fit precisely in depressions on the next brick/cell. 2

Analogies with the familiar

Hooke's original label of the cell was based on a kind of analogy – an attempt to compare what we has seeing with something familiar: "pores, or cells…a great many little Boxes". He used the familiar simile of the honeycomb (something directly familiar to many more people in the seventeenth century when food was not subject to large-scale industrialised processing and packaging).

Other analogies, metaphors and similes abound. Cells are visually like "gloopy balloons", but functionally are "building blocks" (strictly a metaphor, albeit one that is used so often it has become treated as though a literal description) which can be conceptualised as being put together "like you would build a Lego kit" (a simile) although they are neither fixed, discrete blocks of a single material, nor organised by some external builder. They can be considered conceptually as the"smallest unit of life"(though philosophers argue about such descriptions and what counts as an individual in living systems).

The machine description ("fantastical living machines") reflects one metaphor very common in early modern science and cells as "incredible cities" is also a metaphor. Whether cells are literally machines is a matter of how we extend or limit our definition of machines: cells are certainly not actually cities, however, and calling them such is a way of drawing attention to the level of activity within each (often, apparently from observation, quite static) cell. B cells secrete antibodies, which the listener is old are like (a simile) harpoons or missiles – weapons.

Skeletons of the dead

Whether "the cell has its own skeleton" is a literal or metaphorical statement is arguable. It surely would have originally been a metaphoric description – there are structures in the cell which can be considered analogous to the skeleton of an organism. If such a metaphor is used widely enough, in time the term's scope expands to include its new use – and it becomes (what is called, metaphorically) a 'dead metaphor'.

Telling stories about cells

A narrative is used to help a listener imagine the cell at the scale of "a spacecraft". This is "organised into rooms and there are byways and channels" offering an analogy for the complex internal structure of a cell. Most people have never actually boarded a spacecraft, but they are ubiquitous in television and movie fiction, so a listener can certainly imagine what this might be like.

Endoplastic reticulum? (Still from Star Trek: The Motion Picture, Paramount Pictures, 1979)
Oversimplification?

The discussion of organelles illustrates how simplifications have to be made when introducing complex material. This always brings with it dangers of oversimplification that may impede further learning, or even encourage the development of alternative conceptions. So, the nucleus does not, strictly, 'store' "all the genetic information" in a cell (mitochondria carry their own genes for example).

More seriously, perhaps, mitochondria do not "make energy". 'More seriously' as the principle of conservation of energy is one of the most basic tenets of modern science and is considered a very strong candidate for a universal law. Children are often taught in school that energy cannot be created or destroyed. Science communication which is contrary to this basic curriculum science could confuse learners – or indeed members of the public seeking to understand debates about energy policy and sustainability.

Anthropomorphising cells

Cells are not only compared to inanimate entities like balloons, building bricks, cities and spaceships. They are also described in ways that make them seem like sentient agents – agents that have experiences, and conscious intentions, just as people do. So, some immune cells are metaphorical 'first responders' and just as emergency services workers they "rush to the site" of an incident. To rush is not just to move quickly, buy to deliberately do so. (By contrast, Paul McAuley refers to "innocent" amoeboid cells that collectively form into the plasmodium of a slime mould spending most of their lives"bumbling around by themselves" before they "get together". ) The immune cells act deliberately – they "try" to kill. Other immune cells "send out" metaphorical 'missiles' "to kill a pathogen". Again this language suggests deliberate action (i.e., to send out) and purpose.

That is, what is described is not just some evolved process, but something teleological: there is a purpose to sending out antibodies – it is a deliberate act with an aim in mind. This type of language is very common in biology – even referring to the 'function' of the heart or kidney or a reflex arc could be considered as misinterpreting the outcome of evolutionary developments. (The heart pumps blood through the vascular system, but referring to a function could suggest some sense of deliberate design.)

Not all cells are equal

I wonder how many readers noticed the reference above to 'supporting' cells in the heart. Professor Harding had said

"When you look inside the [heart] tissue there are many other cells [than cardiomyocytes] that are in there, supporting it, there are resident macrophages, I think we still don't know really what they are doing in there"

Why should some heart cells be seen as more important and others less so? Presumably because 'the function' of a heart is to beat, to pump, so clearly the cells that pulse are the stars, and the other cells that may be necessary but are not obviously pulsing just a supporting cast. (So, cardiomyocytes are considered heart cells, but macrophages in the same tissue are only cells that are found in the heart, "residents" – to use an analogy of my own, like migrants that have not been offered citizenship!)3

That is, there is a danger here that this way of thinking could bias research foci leading researchers to ignore something that may ultimately prove important. This is not fanciful, as it has happened before, in the case of the brain:

"Glial cells, consisting of microglia, astrocytes, and oligodendrocyte lineage cells as their major components, constitute a large fraction of the mammalian brain. Originally considered as purely non-functional glue for neurons, decades of research have highlighted the importance as well as further functions of glial cells."

Jäkel and Dimou, 2017
The lives of cells

Narrative is used again in relation to the immune cells: an infection is presented as a kind of emergency event which is addressed by special (human like) workers who protect the body by repelling or neutralising invaders. "Sniffing" is surely an anthropomorphic metaphor, as cells do not actually sniff (they may detect diffusing substances, but do not actively inhale them). Even "touching" is surely an anthropomorphism. When we say two objects are 'touching' we mean they are in contact, as we touch things by contact. But touching is sensing, not simply adjacency.

If that seems to be stretching my argument too far, to refer to immune cells "trying to find out…" is to use language suggesting an epistemic agent that can not only behave deliberately, but which is able to acquire knowledge. A cell can only "find" an infectious agent if it is (i.e., deliberately) looking for something. These metaphors are very effective in building up a narrative for the listener. Such a narrative adopts familiar 'schemata', recognisable patterns – the listener is aware of emergency workers speeding to the scene of an incident and trying to put out a fire or seeking to diagnose a medical issue. By fitting new information into a pattern that is familiar to the audience, technical and abstract ideas are not only made easier to understand, but more likely to be recalled later.

Again, an anthropomorphic narrative is used to describe interactions between heart cells. So, a fibroblast that "palpates at" a cardiomyocyte seems to be displaying deliberate behaviour: if "nipping" might be heard as some kind of automatic action – "sampling" and "stroking" surely seem to be deliberate behaviour. A cell that "came in, it went up [to another]" seems to be acting deliberately. "Rearing up" certainly brings to mind a sentient being, like a dog or a horse. Did the cell actually 'rear up'? It clearly gave that impression to Professor Harding – that was the best way, indeed the "only" way, she had to communicate what she saw.

Again we have cells "rushing" around. Or do we? The cell that had reared up, "rushed off". Actually, it appeared to "rush" when the highly magnified footage was played at 720 times the speed of the actual events. Despite acknowledging this extreme acceleration of the activity, the impression was so strong that Professor Harding felt justified in claiming the cell "literally rushed off, although it was time lapse so it was two minutes over 24 hours, so, it literally rushed off…". Whatever it did, that looked like rushing with the distortion of time-lapse viewing, it certainly did not literally rush anywhere.

But the narrative helps motivate a very interesting question, which is why the two superficially similar cells 'behaved' ('reacted', 'responded' – it is actually difficult to find completely neutral language) so differently when in contact with a cardiomyocyte. In more anthropomorphic terms: what had these cells "found, why did one like it and the other one didn't?"

Literally speaking?

Metaphorical language is ubiquitous as we have to build all our abstract ideas (and science has plenty of those) in terms of what we can experience and make sense of. This is an iterative process. We start with what is immediately available in experience, extend metaphorically to form new concepts, and in time, once those have "settled in" and "taken root" and "firmed up" (so to speak!) they can then be themselves borrowed as the foundation for new concepts. This is true both in how the individual learns (according to constructivism) and how humanity has developed culture and extended language.

So, should science communicators (whether scientists themselves, journalists or teachers) try to limit themselves to literal language?

Even if this were possible, it would put aside some of our strongest tools for 'making the unfamiliar familiar' (to broadcast audiences, to the public, to learners in formal education). However these devices also bring risks that the initial presentations (with their simplifications and metaphors and analogies and anthropomorphic narratives…) not only engage listeners but can also come to be understood as the scientific account. That is is not an imagined risk is shown by the vast numbers of learners who think atoms want to fill their shells with octets of electrons, and so act accordingly – and think this because they believe it is what they have been taught.

Does it matter if listeners think the simplification, the analogy, the metaphor, the humanising story,… is the scientific account? Perhaps usually not in the case of the audience listening to a radio show or watching a documentary out of interest.

In education it does matter, as often learners are often expected to progress beyond these introductory accounts in their thinking, and teachers' models and metaphors and stories are only meant as a starting point in building up a formal understanding. The teacher has to first establish some kind of anchor point in the students' existing understandings and experiences, but then mould this towards the target knowledge set out in the curriculum (which is often a simplified account of canonical knowledge) before the metaphor or image or story becomes firmed-up in the learners' minds as 'the' scientific account.

'Building the Body, Opening the Heart' was a good listen, and a very informative and entertaining episode that covered a lot of ideas. It certainly included some good comparisons that science teachers might borrow. But I think in a formal educational context a science teacher would need to be more circumspect in throwing some of these metaphors out there, without then doing some work to transition from them to more technical, literal, and canonical accounts.

Read about science analogies

Read about science metaphors

Read about science similes

Read about anthropomorphism

Read about teleology

Work cited:

Notes:

1 The right hand image portrays a mine, a weapon that is used at sea to damage and destroy (surface or submarine) boats. The mine is also triggered by contact ('touch').

2 That is, in an analogy there are positive and negative aspects: there are ways in which the analogue IS like the target, and ways in which the analogue is NOT like the target. Using an analogy in communication relies on the right features being mapped from the familiar analogue to the unfamiliar target being introduced. In teaching it is important to be explicit about this, or inappropriate transfers may be made: e.g., the atom is a tiny solar system so it is held together by gravity (Taber, 2013).

3 It may be a pure coincidence in relation to the choice of term 'resident' here, but in medicine 'residents' have not yet fully qualified as specialist physicians or surgeons, and so are on placement and/or under supervision, rather than having permanent status in a hospital faculty.

Albert Einstein and John the Baptist

Keith S. Taber

What is the relationship between Albert Einstein and St. John the Baptist?

Why would someone seeking to communicate scientific ideas to a broad readership refer to St. John?

Spoiler alert: in a direct sense, there clearly is no relationship. St. John lived in Palestine two thousand years ago, was a preacher, and is not known to have had any particular interest in what we think of as physics or science more generally. Albert Einstein was a theoretical physicist, and probably the most famous scientist of the twentieth century, perhaps of all time.

It is fair to point out both were Jewish: John can be considered a Jewish prophet. There has been much speculation on Einstein's religious thought. Of Jewish background, he was subject to the Nazi's fascist policies in Germany and fled to spent much of his life in the U.S.A. Sometimes considered an atheist, Einstein did talk of God (as not playing dice for example – that is, not leaving room in the Universe for completely random events) but it is sometimes claimed he use the idea of God as a metaphor for some kind of pantheistic or general spiritual background to the universe. In general though, he stuck to physics, and campaigned on issues like world peace.

(Read about 'The relationship between science and religion')

So, why raise the question?

My posing this question was motivated by reading something written by Herman Weyl (1885 – 1955) who is described by Wikipedia as "a German mathematician, theoretical physicist and philosopher". In one of his writings Weyl referred to Hendrik Lorentz who (again according to Wikipedia) was "a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect".

This is how Weyl described Lorentz:

"the Dutch physicist H.A. Lorentz who, as Einstein's John the Baptist, prepared the way for the gospel of relativity."

Weyl, 1952/2016, pp.131-132.

Those studying physics at high levels, or reading about relativity theory, will probably have heard of the 'Lorentz transformations' that are used in calculations in special relativity.

An extended metaphor?

What Weyl is doing here is using a metaphor, or perhaps an analogy. In a metaphor a writer or speaker says that something is something else – to imply it has some attribute of that other thing.

(Read about 'Science metaphors')

In an analogy, one system is compared with another to show that there is, or to suggest that perhaps might be, a structural similarity. Usually analogies are presented as an explicit comparison (X is like Y: i.e.,  rather than 'Lorentz was Einstein's John the Baptist', perhaps 'Lorentz was like Einstein's John the Baptist in the sense that…')

(Read about 'Science analogies')

As Weyl does not say Lorentz was like a John the baptist figure, or played a role similar to John the Baptist, but that he was "Einstein's John the Baptist" I would consider this a metaphor. However, it is an extended metaphor as the comparison is explained as justified because Lorentz "prepared the way for the gospel of relativity".

That could be seen as a second metaphor in that relativity is normally considered a theory (or two theories, special relativity, and general relativity), and not a gospel – a word that means 'good news'. So Weyl is saying that Lorentz prepared the way for the good news of relativity!

Making the familiar unfamiliar?

When I read this comment I immediately felt I appreciated the point that Weyl was seeking to make. However, I also felt that this was a rather odd comparison to make, as I was not sure how universally it would be understood.

Those communicating about science, whether as science teachers or journalists or (as here) scientists themselves looking to reach a general audience, have the task of 'making the unfamiliar (what people do not yet know about, and may indeed seem odd) familiar'. There are various techniques that can be used, and often these involve some form of comparison of what is being told about with something that is in some ways similar, and which is already familiar to the audience.

(Read about 'Making the unfamiliar familiar')

I attended 'Sunday school' from a young age (I think before starting day school if I recall correctly) at a London City Mission church, and later at a Methodist Church, where I became a Sunday school teacher before i went off to University. I therefore learnt quite a bit about Christianity. Anyone with such a background will have learnt that John the Baptist was a cousin of Jesus Christ, who preached 'the coming of the Lord' (i.e., the Jewish messiah, identified in Christianity with Jesus), and baptised Jesus in the River Jordan as he set out on his mission as a preacher and healer. John is said to have told his congregation to "prepare ye, the way of the Lord!" (the title of a song in the musical 'Godspell').

Someone knowing about Christianity in this way (regardless of whether they accept Christian teaching, or even the historical  accuracy of the Baptism story) would likely immediately appreciate that just as John prepared the way for Jesus' ministry in first Century (CE) Palestine, so, according to Weyl, Lorentz prepared physics, laid important groundwork, for Einstein's work on relativity.

When you have the necessary background, such comparisons work effectively and quickly – the idea is communicated without the reader having to puzzle over and interpret the expressions "Einstein's John the Baptist" and "gospel of relativity"  or deliberate on what is meant by 'preparing the way'. That is, the if the reader has the relevant 'interpretive resources' then understanding is an automatic process that does not require any conscious effort.

Culture-specific interpretive resources?

But I wondered what someone would make of this phrase ('Einstein's John the Baptist') if they did not have knowledge of the Bible stories? After all, in many parts of the world most people are not Christians, and may have little or no knowledge of Christian traditions. Did Weyl just assume everyone would have the background to appreciate his comparison, or did he assume he was only writing for an audience in certain parts of the world where this was common knowledge?

Certainly, as teachers, our attempts to help our students understand abstract ideas by making references to common cultural phenomena can fall flat if the learners are not familiar with those phenomena. It is counter-productive if the teacher has to interrupt their presentation on some abstract idea to explain the very comparison that was meant to help explain the scientific concept or principle. If you have no idea who 'John the Baptist' was, in what sense he 'prepared the way' for Jesus, or or how the term 'Gospel' came to be attached to the accounts of Jesus' life, then it is not so easy to appreciate what Lorentz was to Einstein's work from Weyl's prose. We can only make the unfamiliar familiar by using cultural references when we share those references with those we are communicating with.

Work cited:
  • Weyl, H. (1952/2016). Symmetry (New Princeton Science Library edition ed.). Princeton, New Jersey: Princeton University Press.

 

 

 

 

 

 

Sleep can give us energy

Sleep, like food, can give us a bit more energy

Keith S. Taber

Image by Daniela Dimitrova from Pixabay 

Jim was a participant in the Understanding Science Project. When I was talking to students on that project I would ask them what they were studying in science, rather than ask them about my own agenda of topics. However, I was interested in the extent to which they integrated and linked their science knowledge, so I would from time to time ask if topics they told me about were linked with other topics they had discussed with me. The following extract is taken from the fourth of a sequence of interviews during Jim's first year in secondary school (Y7 in the English school system).

And earlier in the year, you were doing about dissolving sugar. Do you remember that?

Erm, yeah.

Do you think that's got anything to do with the human body?

Erm, we eat sugar.

Mm. True.

Gives us energy…It powers us.

Ah. And why do we need power do you think?

So we can move.

This seemed a reasonable response, but I was intrigued to know if Jim was yet aware of metabolism and how the tissues require a supply of sugar even when there is no obvious activity.

Ah what if you were a lazy person, say you were a very lazy rich person? And you were able to lie in bed all day, watch telly, whatever you like, didn't have to move, didn't have to budge an eyelid, … you're rich, your servants do everything for you? Would you till need energy?

Yes.

Why?

I dunno, 'cause being in bed's tired, tiring.

Is it?

When I'm ill, I stay off for a day, I just feel tired, and like at the end of the day, even more tired than I do when I come to school some times.

Jim's argument failed to allow for the difference in initial conditions

Staying in bed all day and avoiding exercise could indeed make one feel tired, but there seemed something of a confound here (being ill) and I wondered if the reason he stayed in bed on these days might be a factor in feeling even more tired than usual.

So maybe when you are ill, you should come to school, and then you would feel better?

No.

No, it doesn't work like that?

No.

Okay, so why do you think we get tired, when we are just lying, doing absolutely nothing?

Because, it's using a lot of our energy, doing something.

Hm, so even when we are lying at home ill, not doing anything, somehow we are using energy doing something, are we?

Yes.

What might that be, what might we use energy for?

Thinking.

I thought this was a good response, as I was not sure all students of his age would realise that thinking involved energy – although my own conceptualisation was in terms of cellular metabolism, and how thinking depend on transmitting electrical signals along axons and across synapses. I suspected Jim might not have been thinking in such terms.

Do you think it uses energy to think?

(Pause, c.3s)

Probably.

Why do you think that?

Well cause, like, when you haven't got any energy, you can't think, like the same as TV, when it hasn't got any energy, it can't work. So it's a bit like our brains, when we have not got enough energy we feel really tired, and we just want to go to sleep, which can give us more energy, a bit like food.

So Jim here offered an argument about cause and effect- when you haven't got any energy, you can't think. This would certainly be literally true (without any source of energy, no biological functioning would continue, including thinking) although of course Jim had clearly never experienced that absolute situation (as he was still alive to be interviewed), and was presumably referring to experiences of feeling mentally tired and not being able to concentrate.

He offered an analogy, that we are like televisions, in that we do not work without energy. The TV needs to be connected to an electrical supply, and the body needs food (such as sugar, as Jim had suggested) and oxygen. But Jim also used a simile – that sleep was like food. Sleep, like food, according to Jim could give us energy.

So sleeping can give us energy?

Yeah.

How does that work?

Er, it's like putting a battery onto charge, probably, you go to sleep, and then you don't have to do anything, for a little while, and you, then you wake up and you feel – less tired.

Okay so, you think you might need energy to think, because if you have not got any energy, you are very tired, you can't think very well, but somehow if you have a sleep, that might somehow bring the energy back?

Yeah.

So where does that energy come from?

(Pause c.2s)

Erm – dunno.

So here Jim used another analogy, sleeping was like charging a battery. When putting a battery on change, we connect it to a charger, but Jim did not suggest how sleep recharged us, except in that we could rest. When sleeping "you don't have to do anything, for a little while", which might explain a pause in depletion of energy supplies, but would not explain how energy levels were built up again.

[A potentially useful comparison here might have been a television, or a lap top used to watch programmes, with an internal battery, where the there is a buffer between the external supply, and the immediate source for functioning.]

This was an interesting response. At one level it was a deficient answer, as energy is conserved, and Jim's suggestion seemed to require energy to be created or to appear from some unspecified source.

Jim's responses here offered a number of interesting comparisons:

  • sleep is a bit like food in providing energy
  • not having energy and not being able to think is like a TV which cannot work without energy
  • sleeping is like putting a battery on charge

Both science, and science teaching/communication draw a good deal on similes, metaphors and analogies, but they tend to function as interim tools (sources of creative ideas that scientists can then further explore; or means to help someone get a {metaphorical!} foothold on an idea that needs to later be more formally understood).

The idea that sleeping works like recharging a battery could act as an associative learning impediment as there is a flaw in the analogy: putting a battery on charge connects it to an external power source; sleep is incredibility important for various (energy requiring) processes that maintain physical and mental health, and helps us feel rested, but does not in itself source energy. Someone who thought that sleeping works like recharging a battery will not need to wonder how the body accesses energy during sleep as they they seem to have an explanation. (They have access to a pseudo-explanation: sleep restores our energy levels because it is like recharging a battery.)

Jim's discourse reflects what has been called 'the natural attitude' or the 'lifeworld', the way we understand common experiences and talk about them in everyday life. It is common folk knowledge that resting gives you energy (indeed, both exercise and rest are commonly said to give people energy!)

In 'the lifeworld', we run out of energy, we recharge our batteries by resting, and sleep gives us energy. Probably even many science teachers use such expressions when off duty. Each of these notions is strictly incorrect from the scientific perspective. A belief that sleep gives you energy would be an alternative conception, and one that could act as a grounded learning impediment, getting in the way of learning the scientific account.

Yet they each also offer a potential entry point to understanding the scientific accounts. In one respect, Jim has useful 'resources' that can be built on to learn about metabolism, as long as the habitual use of technically incorrect, but common everyday, ways of talking do not act as learning impediments by making it difficult to appreciate how the science teacher is using similar language to express a somewhat different set of ideas.

So who's not a clever little virus then?

The COVID-19 virus is not a clever or sneaky virus (but it is not dumb either) 1

Keith S. Taber

Image by Syaibatul Hamdi from Pixabay 

One of the things I have noticed in recent news reports about the current pandemic is the tendency to justify our susceptibility to the COVID-19 coronavirus by praising the virus. It is an intelligent and sneaky foe, and so we have to outwit it.

But no, it is not. It is a virus. It's a tiny collection of nucleic material packaged in a way that it can get into the cells which contain the chemical resources required for the virus to replicate. It is well suited to this, but there is nothing intelligent about the behaviour. (The virus does not enter the cell to reproduce any more than an ice cube melts to become water; or a hot cup of coffee radiates energy to cool down; or a toddler trips over to graze its knee rather than because gravity acts on it.) The virus is not clever nor sneaky. That would suggest it can adapt its behaviour, after reflecting upon feedback from its interactions with the environment. It cannot. Over generations viruses change – but with a lot of variations that fail to replicate (the thick ones in the family?)

Yet any quick internet search finds references to the claimed intellectual capacities of these deadly foes. Now of course an internet search can find references to virtually anything – but I am referring to sites we might expect to be authoritative, or at least well-informed. And this is not just a matter of a hasty response to the current public health emergency as it is not just COVID 19, but, it seems, viruses generally that are considered intellectually superior.

Those smart little viruses

The site Vaccines Today has a headline in a posting from 2014, that "Viruses are 'smart', so we must be smarter", basing its claims on a lecture by Colin Russell, Royal Society University Research Fellow at Cambridge University. It reports that "Dr Russell says understanding how 'clever' viruses are can help us to outsmart them". (At least there are 'scare quotes' in some of these examples.)

An article from 2002 in an on-line journal has the title "The contest between a clever virus and a facultatively clever host". Now I have moaned about the standard of many new internet journals, but this is the Journal of the Royal Society of Medicine, and the article is in volume 95, so I think it is safe to apply the descriptor 'well-established' to this journal.

A headline in Science news for Students (published by Society for Science & the Public) from 2016 reads "Sneaky! Virus sickens plants, but helps them multiply". I am sure it would not take long to find many other examples. An article in Science refers to a "nasty flu virus".

Sneaky viruses

COVID-19 is a sneaky virus according to a doctor writing in the Annals of Internal Medicine. Quite a few viruses seem to be sneaky – the the human papillomavirus is according to an article in the American Journal of Bioethics. The World Health Organisation considers that a virus that causes swine fever, H1N1, is sneaky according to an article in Systematic Reviews in Pharmacy, something also reported by the BMJ.

There are many references in the literature to clever viruses, such as Epstein‐Barr virus according to a piece in the American Journal of Transplantation. The Hepatitis C virus is clever according to an article in Clinical Therapeutics.

Science communication as making the unfamiliar, familiar

Science communication is a bit like teaching in that the purpose of communication is often to be informative (rather than say, social cohesion, like a lot of everyday conversation {and, by the way,it was another beautiful day here in Cambridgeshire today, blue sky – was it nice where you are?}) and indeed to make the unfamiliar, familiar. Sometimes we can make the unfamiliar familiar by showing people the unfamiliar and pointing it out. 'This is a conical flask'. Often, however, we cannot do that – it is hard to show someone hyperconjugation or hysteresis or a virus specimen. Then we resort to using what is familiar, and employing the usual teacher tricks of metaphor, analogy, simile, modelling, graphics, and so forth. What is familiar to us all is human behaviour, so personification is a common technique. What the virus is doing, we might suggest, is hijacking the cell's biochemical machinery, as if it is a carefully planned criminal operation.

Strong anthropomorphism and dead metaphors

This is fine as far as it goes – that is, if we use such techniques as initial pedagogic steps, as starting points to develop scientific understanding. But often the subsequent stage does not happen. Perhaps that is why there are so many dead metaphors in the language – words introduced as metaphors, which over time have simple come to be take on a new literal meaning. Science does its fair share of borrowing – as with charge (when filling a musket or canon). Dead metaphors are dead (that is metaphorical, of course, they were never actually alive) because we simply fail to notice them as metaphors any more.

There are probably just as many references to 'clever viruses' referring to computer viruses as to microbes – which is interesting as computer viruses were once only viruses metaphorically, but are now accepted as being another type of virus. They have become viruses by custom and practice, and social agreement.

Whoever decided to first refer to the covalent bond in terms of sharing presumably did not mean this in the usual social sense, but the term has stuck. The problem in education (and so, presumably, public communication of science) is that once people think they have an understanding, an explanation that works for them, they will no longer seek a more scientific explanation.

So if the teacher suggests an atom is looking for another electron (a weak form of anthropomorphism, clearly not meant to be taken too seriously – atoms are not entities able to look for anything) then there is a risk that students think they know what is going on, and so never seek any further explanation. Weak anthropomorphism becomes strong anthropomorphism: the atom (or virus) behaves like a person because it has needs and desires just like anyone else.

Image by Tumisu from Pixabay 

Why does it matter?

Perhaps in our current situation this is not that important – the public health emergency is a more urgent issue than the public understanding of the science. But it does matter in the long term. Viruses are not clever – they have evolved over billions of years, and a great many less successful iterations are no longer with us. The reason it matters is because evolution is often not well understood.

As an article in Evolution News and Science Today (a title that surely suggests a serious science periodical about evolution) tells us again that "Viruses are, to all appearances, very clever little machines" and asks "do they give evidence of intelligent design" (that is, rather than Darwinian natural selection, do they show evidence of having an intelligent designer?) After exploring some serious aspects of the science of viruses, the article concludes: "So it seems that viruses are intelligently designed" – that is, a position at odds with the scientific understanding that is virtually a consensus view based on current knowledge. Canonical science suggests that natural processes are able to explain evolution. But these viruses are so clever they must surely have been designed (Borg technology, perhaps?)

This is why I worry when I hear that viruses are these intelligent, deliberate agents that are our foes in some form of biological warfare. It is a dangerous way of thinking. So, I'm concerned when I read, for example, that the cytomegalovirus is not just a clever virus but a very clever virus. Indeed, according to an article in Cell Host & Microbe "CMV is a very clever virus that knows more about the host immune system and cell biology than we do". Hm.

(Read about 'anthropomorphism')

Footnote:

1. The subheading was amended on 4th October 2021, after it was quite rightly pointed out to me that the original version, "COVID-19 is not a clever or sneaky virus (but it is not dumb either)", incorrectly conflated the disease with the virus.

Peter and Patricia Pigeon set up house together

Keith S. Taber

In my work I've spent a lot of time analysing the things learners say about science topics in order to characterise their thinking. Although this work is meant to have an ethnographic feel, and to be ideographic (valuing the thinking of the individual in its own terms), there is always an underlying normative aspect: that is, inevitably there is a question of how well learners' conceptualisations match target curricular knowledge and canonical science. We all have intuitions which are at odd with scientific accounts of the world, and we all develop alternative conceptions – notions which are inconsistent with canonical concepts.

Peter and Patricia started seeing each other at this local fence earlier this year.

Soon passion got too much for them and they (publicly) consummated their relationship on this very fence (some birds have no shame).

It is easier to spot this in others (you think what?!) than it is in ourselves. But occasionally you may reflect on the way you think about a topic and recognise aberrations in your own thinking. One of these examples in my own thinking relates to bird's nests. I know that birds build nests as a place to lay and hatch eggs. Using the ground would be very dangerous due to vulnerability to predators. Simply using branches would be precarious – especially as eggs are hardly best shaped to be balanced on a tree branch. I also know that once the young are fledged have fled the nest, it has outlived its purposes.

They quite liked the area, and decided to look for a place nearby.

Soon they had identified a nice place to build their new home in some nearby ivy.

Yet it was only a few years ago – I think when came across discarded nests in the garden – that I released I have carried around with me since quite young the metaphor that a nest is a bird's home – it is where the bird family lives. Perhaps I made up that idea as a child. More likely I was told that or heard it on a children's programme. If so, perhaps it was not meant to be taken too literally – it was just meant to compare the nest with something that would be familiar to a child. But I think well into adulthood I had this notion of that birds lived in trees – not explicitly, but insidiously in the back of my mind: as if a bird had a home in a tree and that was where it was based – unless and until perhaps it could afford to move upmarket to a better tree!

They decided to do their own build, which involved Peter in the tiring work of going out to get building materials.

Peter set about the serious business of setting up their new dream home.

Peter was quite confident, and would often return which rather large pieces of nesting material.

"Oh, that seems to have got caught up."

Over time Peter started to be more realistic in selecting material he could get through the front door.

Although I was well aware (at one level) that birds do not have permanent family homes to which they return at the end of a hard day's exertions, I also had this nest=home identity at the 'back of my mind' giving the impression that this is how birds live. As humans we take for granted certain kinds of forms of life (perhaps home, work, family, etc.), and these act as default templates for understanding the world. This makes anthropomorphising nature seem quite a natural thing to do.

Peter heading out to work, again.

And getting home with his latest acquisition – landing on his feet.

Watching this process develop was quite entertaining. Peter would spend ages pecking at pieces of plant that were firmly fixed in the ground, ignoring nearby loose material. His early attempts to take material back to the nest were troubled. He would take material that was too large to get through the foliage into the secluded nesting area. He would also fly close to 'home' and then abort as found he could not land with his goods. However, he soon seemed to learn what worked, and developed a technique of first flying onto the fence or the roof the ivy was growing on to, so he would not be flying up to the nesting place from the ground in a single stage.

The sequences below show the pigeon flying out from, and back to, the nest.

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The jumping/diving action is clear in the sequence below:

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The fourth and fifth frames in the sequence below show the 'landing gear' coming into position (reminiscent of a bird of prey taking its prey):

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The landing action is also clear near the end of the sequence below:

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Another take off. catching the first few flaps:

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My favourite sequence – quite extended for my hand-held camera work! – in the 11th frame our pigeon is just entering frame right. But notice a sparrow sitting on top of the foliage to the left. The sparrow has presumably seen/heard the much larger bird comings it way, and in the next frame can be seen to be moving its wings ready to take off. The next three frames have the sparrow heading right as the pigeon moves to the left (the sparrow is a smudge beneath the pigeon's left wing in the third of these frames), and the sparrow appears to have disappeared from view in the next, but must have been obscured by the pigeon as it seen to the right of the next frame. The sequence ends with the pigeon in landing mode.

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Current only slows down at the resistor

Current only slows down at the resistor – by analogy with water flow 

Keith S. Taber

Students commonly think that resistance in a circuit has local effects, and in part that is because forming a mental model of what is going on in circuits is very difficult. Often models and analogies can be useful. However when an analogy is used in teaching there is also the potential for it to mislead.

Amy was a participant in the Understanding Science Project. Amy (when in Y10) told me she had been taught to use a water flow analogy for electric current. However, because her visualisation of what happens in water circuits was incorrect, she used the analogy to inform an alternative conception about circuits:

Do you have any kind of imagined sort of idea, any little mental models, about what (the flow of electricity round the circuit) might look like? Do you have a way of imagining that?

Erm, yeah, we've been taught the water tank and pipe running round it. … just imagine the water like flowing through a pipe, and obviously like, if the pipe becomes smaller a one point, erm, the water flow has to slow down, and that's meant to represent the resistance of something.

So, so if I had my water, er, tank and I had a series of pipes, they'd be water flowing through the pipes, and if I had a narrower pipe at one point, what happens then?

The water would have to slow down.

So would it slow down just as it goes through the narrow pipe, or would it slow down all the way round?

Erm – just through that part.

(Amy does not appreciate the implications of conservation of mass {that is, the continuity principle} here – at steady state there cannot be a greater mass flow at different points in the circuit).

…

And so how do you imagine that's got to do with resistance, how does that help you understand resistance?

…well resistance, it slows the current down, but then erm, once it passes a resistor or something it, the current is free to flow through the wire again

Analogies can be very useful teaching tools, but when using them it is important to check that the students already understand the features of the analogue that are meant to be helpful. It is also important to ensure that they understand which features are meant to be mapped onto the target system they are learning about, and which are not relevant.

Analogies are only useful when the learner has a good understand of the analogue. In this case, as Amy did not appreciate that the water flow throughout the system would be limited by the constriction, she could not use that as a useful analogy for why a resistor influences current flow at all points in a series circuit. This is an example of where a teaching model meant to support learning, which actually misleads the learner. That is, for Amy, with her flawed understanding of fluid flow, the teaching model acted as a pedagogic learning impediment – a type of grounded learning impediment.

Molecules are like a jigsaw

Keith S. Taber

Tim was a participant in the Understanding Science Project. When Tim was interviewed in the first term of his 'A level' (college level) physics course he had been studying the topic of materials with one of his teachers, and "at the moment we're doing about why some materials are brittle, and some aren't, and about the molecules". When Tim was asked about the molecules, he compared molecules to the pieces in a jigsaw:

Interviewer: So what's a molecule?

Tim: Erm it's like a bit of a particle, so, something that makes up something.

I: Have you got any examples?

T: Of a molecule?

I: Yeah, something that makes up something.

T: Erm, like the wood in the table is made out of wood molecules.

I: I see. So, that's one type of molecule, is it, a wood molecule? And there are other types of molecule?

T: Yes it's a bit like a jigsaw, like when you put all the, like you need to put the…, you put them all together to make – something.

I: I see, yeah. So, if I wanted to be really awkward, in what way is it like a jigsaw?

T: Erm, well they sort of fit together, like in a jigsaw some bits are sort of straight and have nice parallel, a nice parallel microstructure, and some, some jigsaws have funny bits that don't fit together quite as nicely.

I: I see. So are there some ways it's not like a jigsaw?

T: Yeah. (Tim laughs.) Well, erm, I dunno, it's like a jigsaw in the way that the bits fit together to make something, to make something, but then again, I dunno.

I: I mean, I quite like this idea of it being like a jigsaw – I was wondering whether, whether you had got that from somewhere, or that's just something you'd come up with?

T: No I just thought about it, just then.

I: Oh that's really creative.

T: It's quite random actually. (laughs)

Tim's comments about a molecules being a bit of a particle was followed up later in the interview, and it transpired he was not sure if a molecule is a bit of a particle – or vice versa.*

So when asked to explain about molecules in materials, Tim used an apparently spontaneous analogy of this being like a jigsaw, with different types of pieces that fitted together. Moreover, he also seemed to recognise that different materials had molecules that fitted together more or less readily, and materials could also be considered to have similar diversity. Tim described this as being 'random', which seems unfair as the analogy clearly has merit, but presumably saw it this way as the comparison had apparently appeared in his consciousness unexpectedly (i.e., the thought had 'popped into his mind', as a kind of insight.)

Tim seemed a little phased by being asked to explain the negative features of the analogy – and this may reflect the tendency to focus on the positive aspects of an analogy, rather than its limitations. Analogy has the potential to channel student thinking in inappropriate directions (e.g., as associative learning impediments) when not considered critically. However, analogies also have potential to help 'make the unfamiliar familiar' and so can be a powerful learning tool.