A faecal transplant is like wild flower seeds in some soil
Keith S. Taber
"Many animals naturally ate each other's poo…as a way of staying healthy" Prof. Tim Spector. (Original image by Debbie De Jager from Pixabay, with apologies to Monty Python)
I was listening to a podcast from 'Science Stories' (BBC Radio 4) about 'Lady Mary Montagu's Smallpox Experiment', where Naomi Alderman described how the aforementioned Lady Mary Wortley Montagu brought the practice of opening veins to introduce some smallpox into the body, as a way of protecting against the deadly disease, back from Turkey to Britain.
This was compared with the process of faecal transplantation which was apparently first used in China, and is increasingly being seen as a valuable treatment for some gut disorders. This is the process of ingesting, under carefully controlled conditions, some human faeces – either some of your own carefully preserved (for example, some cancer patients have a sample collected and stored before starting chemotherapy), or from some donor who is willing to offer some of their own. Unlike some other donor procedures (such as kidney donation) this is non-invasive and concerns material most of us just dispose of anyway!
Tim Spector, Professor of Genetic Epidemiology at Kings College, London explained the significance of the gut microbiome, the community of something like 100 trillion microbes that typically occupy a human gut. The importance of these organisms for human health is increasingly being appreciated.
Treating Clostridium difficile infection
Disturbances of the gut microbiome can lead to ill health. One particular example is the condition known as Clostridium difficile infection ('C. diff') – which is commonly experienced in hospitals when patients have extensive courses of antiobiotics – which can sadly kill the useful gut microbes as well those disease-causing organisms being targeted. Clostridium difficile (being itself unaffected by many commonly used antibiotics) can in these circumstances reproduce rapidly and vastly increase its numbers. This is problematic as the organism releases a toxin.
C. diff infection can lead to the sufferer needing to visit the toilet urgently and repeatedly – many times each day. This is not only undesirable in itself, but interferes with getting nutrition from food (if the person has any appetite to eat), and leads to dangerous dehydration – and can have other complications. So, this is a very serious condition, and it is readily transmitted from one person to another.
"C. difficile is an infectious Gram-positive spore-forming bacillus microorganism of the gastrointestinal tract, and its toxin expression causes gastrointestinal illness with a wide spectrum of severity, ranging from mild diarrhea to pseudomembranous colitis, toxic megacolon, sepsis-like picture and death…"
Bien, Palagan & Bozko, 2013: 53
Many people have a low level of Clostridium difficile specimens in their gut normally, but as one small part of the much larger and diverse population of gut microbes – in which context they cause no problems.
"C. difficile does not cause any significant disease when it is present in small numbers. However, disturbance of the normal intestinal flora (dysbiosis) by several potential causative factors may result in unlimited [sic] expansion of C. difficile in the microbiota, leading to inflammation and damage of the gut mucosa…"
Bien, Palagan & Bozko, 2013: 56
Someone who has suffered from C. diff infection needs a way to repopulate their gut with a good range of the usual different microbes. And that is when consuming a sample of a healthy person's excrement can be useful. (This is of course done under medical direction and supervision, both to maintain hygiene and to ensure the donor does not have medical conditions that might be passed on with the sample.)
A teaching analogy for faecal transplantation
This was all explained by Prof. Spector using an analogy.
Analogies are comparisons where a less familiar, and perhaps abstract or counterintuitive, concept is explained in terms of something familiar that can be seen to have a similar conceptual structure (see the figure). Analogies are commonly used in science teaching and public communication of science (as here in a radio programme) to introduce scientific ideas.
Prof. Spector developed a comparison between the different microbes found in the gut, and the plants growing in a garden:
"These nasty infections are the most extreme, if you like, that pretty much wipe out most of our normal species. So … we might, say, start with a thousand species and people [with C. diff] might be down to just ten or so, different ones and so nasty ones take over. It's a bit like a garden that has gone very badly wrong and you have put too much herbicide all over it and it looks like an Arizona back yard with a few burning tyres in it. It's very easy for things to take over that and what we want to get, is by putting these bugs in there, to create a really healthy garden that gets back to normal that looks like a nice English country garden with lots of blooms, and really good soil, and lots of plants interacting with each other, and that's the way to think about these microbes, but to do that, to get to this nice rosy picture of a country garden you have to go through yucky stages first"
Before and after faecal transplantation: a medical treatment that can transform your 'garden'? (Images by Simon (left) and Prawny (right) from Pixabay) [Move the slider to change between the pictures].
So the idea of taking a sample of someone else's excrement into our own gut may seem "yukky" – and is definitely NOT recommended without proper procedures and supervision – but may sometimes be a sensible and beneficial medical treatment. Just think of it as resewing the garden of the gut with a nice selection of seeds that will give rise to a diverse selection of colourful blooms.
Naomi Alderman: Instead of poo, we could think to ourselves, 'wild flower seeds'
Tim Spector: It's wild flower seeds with a bit of soil in it as well, so they have come in their own pot [sic] if you like.
'wild flower seeds with a bit of soil…in their own pot'? (Images by OpenClipart-Vectors from Pixabay)
Work cited:
Bien, J., Palagani, V., & Bozko, P. (2013). The intestinal microbiota dysbiosis and Clostridium difficile infection: is there a relationship with inflammatory bowel disease? Therapeutic advances in gastroenterology, 6(1), 53-68. doi:10.1177/1756283X12454590 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3539291/
As part of the primary scientific literature, it publishes articles written by specialist scientists in a technical language intended to be understood by other specialists. Dense scientific terminology is not used to deliberately exclude general readers (as sometimes suggested), but is necessary for scientists to make a convincing case for new knowledge claims that seem persuasive to other specialists. This requires being precise, using unambiguous technical language."The thingamajig kind of, er, attaches to the erm, floppy bit, sort of" would not do the job.
Science News however is news media – it publishes journalism (indeed, 'since 1921' the site reports – although that's the publication and not its website of course.) While science journalism is not essential to the internal processes of science (which rely on researchers engaging with each other's work though scholarly critique and dialogue) it is very important for the public's engagement with science, and for the accountability of researchers to the wider community.
Science journalists have a job similar to science teachers – to communicate abstract ideas in a way that makes sense to their audience. So, they need to interpret research and explain it in ways that non-specialists can understand.
The news article told me
"Like a shaggy dog in springtime, some black holes have to shed… Unlike dogs with their varied fur coats, isolated black holes are mostly identical. They are characterized by only their mass, spin and electric charge. According to a rule known as the no-hair theorem, any other distinguishing characteristics, or "hair," are quickly cast off. That includes magnetic fields."
Conover, 2013
Here there is clearly the use of an analogy – as a black hole is not the kind of thing that has actual hair. This would seem to be an example of a journalist creating an analogy (just as a science teacher would) to help 'make the unfamiliar familiar' to her readers:
just as
dogs with lots of hair need to shed some ready for the warmer weather (a reference to a familiar everyday situation)
so, too, do
black holes (no so familiar to most people) need to lose their hair…
Surely a better analogy would be along the lines that just as dogs with lots of hair need to shed some ready for the warmer weather, so to do black holes need to lose their magnetic fields…
An analogy is used to show a novel conceptual structure (here, relating to magnetic fields around black holes) maps onto a more familiar, or more readily appreciated, one (here, that a shaggy dog will shed some of its fur). A teaching analogy may not reflect a deep parallel between two systems, as its function may be just to introduce an abstract principle.
Conover did not invent the 'hair' reference for her ScienceNews piece – rather she built her analogy on a term used by the scientists themselves. Indeed, the title of the cited research journal article was "Magnetic Hair and Reconnection in Black Hole Magnetospheres", and it was a study exploring the consequences of the "no-hair theorem" – as the authors explained in their abstract:
"The no-hair theorem of general relativity states that isolated black holes are characterized [completely described] by three parameters: mass, spin, and charge."
Bransgrove, Ripperda & Philippov, 2021
However, some black holes "are born with magnetic fields" or may "acquire magnetic flux later in life", in which case the fields will vary between black holes (giving an additional parameter for distinguishing them). The theory suggests that these black holes should somehow lose any such field: that is, "The fate of the magnetic flux (hair) on the event horizon should be in accordance with the no-hair theorem of general relativity" (Bransgrove, Ripperda & Philippov, 2021: 1). There would have to be a mechanism by which this occurs (as energy will be conserved, even when dealing with black holes).
So, the study was designed to explore whether such black holes would indeed lose their 'hair'. Despite the use of this accessible comparison (magnetic flux as 'hair'), the text of the paper is pretty heavy going for someone not familiar with that area of science:
"stationary, asymptotically flat BH spacetimes…multipole component l of a magnetic field…self-regulated plasma…electron-positron discharges…nonzero stress-energy tensor…instability…plasmoids…reconnection layer…relativistic velocities…highly magnetized collisionless plasma…Lundquist number regime…Kerr-schild coordinates…dimensionless BH spin…ergosphere volume…spatial hypersurfaces…[…and so it continues]"
(Bransgrove, Ripperda & Philippov, 2021: 1).
"Come on Harry, you know full well that 'the characteristic minimum plasma density required to support the rotating magnetosphere is the Goldreich-Julian number density' [Bransgrove, Ripperda & Philippov, 2021: 2], so hand me that hyperspanner." Image from Star Trek: Voyager (Paramount Pictures)
Spoiler alert
I do not think I will spoil anything by revealing that Bransgrove and colleague conclude from their work that "the no-hair theorem holds": that there is a 'balding process' – the magnetic field decays ("all components of the stress-energy tensor decay exponentially in time"). If any one reading this is wondering how they did this work, given that most laboratory stores do not keep black holes in stock to issue to researchers on request, it is worth noting the study was based on a computer simulation.
That may seem to be rather underwhelming as the researchers are just reporting what happens in a computer model, but a lot of cutting-edge science is done that way. Moreover, their simulations produced predictions of how the collapsing magnetic fields of real black holes might actually be detected in terms of the kinds of radiation that should be produced.
As the news item explained matters:
Magnetic reconnection in balding black holes could spew X-rays that astronomers could detect. So scientists may one day glimpse a black hole losing its hair.
Conover, 2013
So, we have hairy black holes that go through a balding process when they lose their hair – which can be tested in principle because they will be spewing radiation.
Balding is to hair, as…
Here we have an example of an analogy for a scientific concept. Analogies compare one phenomenon or concept to another which is considered to have some structural similarity (as in the figure above). When used in teaching and science communication such analogies offer one way to make the unfamiliar familiar, by showing how the unfamiliar system maps in some sense onto a more familiar one.
hair = magnetic field
balding = shedding the magnetic field
Black holes are expected to be, or at least to become, 'hairless' – so without having magnetic fields detectable from outside the event horizon (the 'surface' connecting points beyond which everything, even light, is unable to 'escape' the gravitational field and leave the black hole). If black holes are formed with, or acquire, such magnetic fields, then there is expected to be a 'balding' process. This study explored how this might work in certain types of (simulated) black holes – as magnetic field lines (that initially cross the event horizon) break apart and reconnect. (Note that in this description the magnetic field lines – imaginary lines invented by Michael Faraday as a mental tool to think about and visualise magnetic fields – are treated as though they are real objects!)
Some such comparisons are deliberately intended to help scientists explain their ideas to the public – but scientists also use such tactics to communicate to each other (sometimes in frivolous or humorous ways) and in these cases such expressions may do useful work as short-hand expressions.
So, in this context hair denotes anything that can be detected and measured from outside a black hole apart form its mass, spin, and charge (see, it is much easier to say 'hair')- such as magnetic flux density if there is a magnetic field emerging from the black hole.
A dead metaphor?
In the research paper, Bransgrove, Ripperda and Philippov do not use the 'hair' comparison as an analogy to explain ideas about black holes. Rather they take the already well-established no-hair theorem as given background to their study ("The original no-hair conjecture states that…"), and simply explain their work in relation to it ("The fate of the magnetic flux (hair) on the event horizon should be in accordance with the no-hair theorem of general relativity.")
Whereas an analogy uses an explicit comparison (this is like that because…), a comparison that is not explained is best seen as a metaphor. A metaphor has 'hidden meaning'. Unlike in an analogy, the meaning is only implied.
"The no-hair theorem of general relativity states that isolated black holes are characterized by three parameters: mass, spin, and charge";
"The original no-hair conjecture states that all stationary, asymptotically flat BH [black hole] spacetimes should be completely described by the mass, angular momentum, and electric charge"
Bransgrove and colleagues do not need to explain why they use the term 'hair' in their research report as in their community it has become an accepted expression where researchers already know what it is intended to mean. We might consider it a dead metaphor, an expression which was originally used to imply meaning through some kind of comparison, but which through habitual use has taken on literal meaning.
Science has lots of these dead metaphors – terms like electrical charge and electron spin have with repeated use over time earned their meanings without now needing recourse to their origins as metaphors. This can cause confusion as, for example, a learner may develop alternative conceptions about electron spin if they do not appreciate its origin as a metaphor, and assumes an electron spins in the same sense as as spinning top or the earth in space. Then there is an associative learning impediment as the learner assumes an electron is spinning on its axis because of the learner's (perfectly reasonable) associations for the word 'spin'.
The journalist or 'science writer' (such as Emily Conover), however, is writing for a non-specialist readership, so does need to explain the 'hair' reference. So, I would characterise the same use of the terms hair/no-hair and balding as comprising a science analogy in the news item, but a dead metaphor in the context of the research paper. The meaning of language, after all, is in the mind of the reader.
Is the work of cognition like the work of a palaeontologist? (Image by Brenda Geisse from Pixabay)
I like the reflexive nature of this account – of someone reconstructing an analogy
abouthow cognition reconstructs coherent wholes from partial, fragmented data
froma partial, fragmented memory representation.
I was reading something about memory function that piqued my interest in an analogy:
"Neisser, using an analogy initially developed by Hebb (1949) to characterize [sic] perception, likened the rememberer to a paleontologist who attempts to reconstruct a dinosaur from fragmentary remains: 'out of a few stored bone chips, we remember a dinosaur'…"
Schacter, 1995, p.10
I was interested enough to look up the original use of this analogy (as I report below).
This links to three things that have separately interested me:
using analogies in teaching and comunicating science
The nature of our memories
I have long been interested in what memory is and how it works – and its role in academic learning (Taber, 2003). In part this perhaps derives from the limits of my own memory – I have been reasonably successful academically, but have never felt I had a good memory (and I seem to get more 'absent minded' all the time). This interest grew as it became clearer to me that our memory experiences seem to be quite different – my late wife Philippa would automatically and effortlessly remember things in a way that that seemed to me to be a kind of superpower. (She was once genuinely surprised that I could not picture what a family member had been wearing on arriving at a family event years before, whereas I thought I was doing pretty well to even remember I had been there.) Now that neurodiversity is widely recognised, it seems less surprising that we do not all experience memory in the same way.
A lot of people, however, understand memory in terms of a kind of folk-model (that is, a popular everyday account which does not match current scientific understanding) – along the lines that we put information into a memory store, where – unless it gets lost and we forget – we can later access it and so remember what it was that we committed to memory. Despite the ubiquity of that notion, research suggests that is not really how memory functions. We might say that this is a common alternative conception of how memory works.
Schacter was referring back to a tradition that began a century ago when Bartlett carried out a series of studies on memory. Bartlett (1932/1995) would, for example, expose people to a story that was unfamiliar to his study participants, and then later ask them to retell as much of the story as they could remember. As might be expected, some people remembered more details than others.
What perhaps was less predictable at the time was the extent to which people included in their retelling details that had not been part of the original story at all. These people were not deliberately embellishing or knowingly guessing, but reporting, as best they could, what their memory suggested had been part of the original story.
People who habitually exhibit this 'confabulation' to an pathological degree (perhaps remembering totally fantastic things that clearly could not be true) are recognised as having some kind of problem, but it transpires this is just an extreme of something that is normal behavior. Remembering is not the 'pulling something out of storage' that we may experience it as – as actually what we remember is more like a best guess based on insufficient data (but a guess made preconsciously, so it appears in our conscious minds as definitive) than a pristine copy of an original experience. Memory is often more a matter of constructing an account from the materials at hand than simply reading it out from something stored.
Thus the analogy. Here is some wider context for the quote presented above:
"The publication of Neisser's (1967) important monograph on cognitive psychology rekindled interest in Bartlett's ideas about schemas and reconstructive memory. According to Neisser, remembering the past is not a simple matter of reawakening a dormant engram or memory trace; past events are constructed by using preexisting knowledge and [schemata] to piece together whatever fragmentary remains of the initial episode are available in memory. Neisser, using an analogy initially developed by Hebb (1949) to characterize [sic] perception, likened the rememberer to a paleontologist who attempts to reconstruct a dinosaur from fragmentary remains: 'out of a few stored bone chips, we remember a dinosaur' (1967, p.285). In this view, all memories are constructions because they include general knowledge that was not part of a specific event, but is necessary to reconstruct it. The fundamentally constructive nature of memory in turn makes it susceptible to various kinds of distortions and inaccuracies. Not surprisingly, Neisser embraced Bartlett's observations and ideas about the nature of memory."
Schacter, 1995, p.10
These ideas will not seem strange to those who have studied science education, a field which has been strongly influenced by a 'constructivist' perspective on learning. Drawing on learning science research, the constructivist perspective focuses on how each learner has to build up their own knowledge incrementally: it is not possible for a teacher to take some complex technical knowledge and simply transfer it (or copy it) to a learner's mind wholesale.
Excavating the analogy: what did Hebb actually say?
Hebb is remembered for his work on understanding the brain in terms of neural structures – neurons connected into assemblies through synapses. His book 'The Organization of Behavior' has been described as "one of the most influential books in Psychology and Neuroscience" (Brown, 2020: 1).
The analogy referred to by Schacter was used by Hebb in describing perception. He discussed studies using a tachistoscope, an instrument for displaying images for very brief periods. This could be used to show an image to a person with an exposure insufficient for them to take in all the details,
"…the pattern is perceived, first, as a familiar one, and then with something missing or something added. The something, also, is familiar; so the total perception is a mélange of the habitual.
The subject's reports [make it] clear that the subject is not only responding to the diagram as a whole; he perceives its parts as separate entities, even though presentation is so brief. Errors are prominent, and such as to show that all the subject really perceives–and then only with rough accuracy–is the slope of a few lines and their direction and distance from one another"
Hebb, 1949: pp.46-47
That is, the cognitive system uses the 'clues' available from the incomplete visual data to build (in effect) a hypothesis of what was seen, based on correspondences between the data actually available and familiar images that match that limited data. What the person becomes consciously aware of 'seeing' is not actually a direct report from the visual field of the presented image, but a constructed image that is a kind of conjecture of what might have been seen – 'filling-in' missing data with what seems most likely based on past visual experiences.
Cognitive scientist Annette Karmiloff-Smith developed the concept of 'representational redescription' as a way of describing how initially tacit knowledge could eventually become explicit. She suggested that "intra-domain and inter-domain representational relations are the hallmark of a flexible and creative cognitive system" (Karmiloff-Smith,1996: 192). The gist was that the brain is able to re-represent its own internal representations in new forms with different affordances.
An loose analogy might be someone who takes a screenshot when displaying an image from the JPEG photo collection folder on the computer, opens the screenshot as a pdf file, and then adds some textual annotations before exporting the file to a new pdf. The representation of the original image is unchanged in the system, but a new representation has been made of it in a different form, which has then been modified and 'stored' (represented) in a different folder.
Hebb was describing how a representation of visual data at one level in the cognitive system has been represented elsewhere in the system (representational redescription?) at a level where it can be mentipulated by 'filling-in'.
"A drawing or a report of what is seen tachistoscopically is not unlike a paleontologist's reconstruction of early man from a tooth and a rib. There is a clear effect of earlier experience, filling in gaps in the actual perception, so that the end result is either something familiar or a combination of familiar things–a reconstruction on the basis of experience."
Hebb, 1949: p.47
Teaching analogies
Hebb was writing a book that can be considered as a textbook, so this can be seen as a teaching analogy, although such analogies are also used in communicating science in other contexts.
Teaching is about making the unfamiliar familiar, and one way we do that is by saying that 'this unfamiliar thing you need to learn about is a bit like this other thing that you already know about'. Of course, when teaching in this way we need to say in what way there is an analogy, and it may also be important to say in what ways the two things are not alike if we do not want people to map across irrelevant elements (i.e., to develop 'associative' learning impediments).
Hebb is saying that visual perception is often not simply the detection of a coherent and integral image, but is rather a construction produced by building upon the available data to construct a coherent and integral image. In extremis, a good deal may be made of very little scraps of input – akin to a scientist reconstructing a model of a full humanoid body based on a couple of bits of bone or tooth.
There are examples where palaeontologists or anthropologists have indeed suggested such complete forms based on a few fossil fragments as data. This is only possible because of their past experiences of meeting many complete forms, and the parts of which they are made. (And of course, sometimes other scientists completely disagree about their reconstructions!)
An exscientific analogy?
Often in teaching science we use teaching analogies that compare an unfamiliar scientific concept to some familiar everyday phenomenon – perhaps a reaction profile is a bit like a roller-coaster track. Perhaps we could call these adscientific analogies as the meaning is transferred to the scientific concept from the everyday.
Sometimes, however, familiar scientific phenomena or ideas are used as the source – as here. Perhaps these could be called exscientific analogies as the meaning is taken from the science concept and applied elsewhere.
Developing the palaeontology analogy
So, Hebb had originally used the palaeontology analogy in the context of discussing perception. When I looked into how Neisser had used the comparison in his "important monograph on cognitive psychology" I found he had developed the analogy, returning to it at several points in his book.
Do we analyse what we attend to?
Neisser's first reference was also in relation to perception, rather than memory. Neisser argued that before we can attend to part of a scene there must already have been the operation of "preattentive mechanisms, which form segregated objects" from which we can select what to attend to. These processes might be referred to as analyses:
"…the detailed properties and features that we ordinarily see in an attended figure…arise…only because part of the input was selected for attention and certain operations then performed on it. Neither the object of analysis nor the nature of the analysis is inevitable, and both may vary in different observers and at different times."
Neisser, 1967, p.94
But Neisser was not sure this really was 'analysis', which he understood as drawing on another (what I labelled above) exscientific analogy:
"The very word 'analysis' may not be apt. It suggests an analogy with chemistry: a chemist 'analyses' unknown substances to find out what they 'really' are."
Neisser, 1967, p.94
Rather than refer to analysis, we could draw on Hebb's palaeontological analogy:
"More appropriate…is Hebb's (1949, p.47) comparison of the perceiver with a paleontologist, who carefully extracts a few fragments of what might be bones from a mass of irrelevant rubble and 'reconstructs' the dinosaur that will eventually stand in the Museum of Natural History. In this sense it is important to think of focal attention as a constructive, synthetic activity rather than as purely analytic. One does not simply examine the input and make a decision; one builds an appropriate visual object."
Neisser draws upon the analogy repeatedly in developing his account of perception:
"Such emotion-flooded experiences [as 'physiognomic' perception: 'Everyone has perceived such traits as suppressed anger in a face, gaiety in a movement, or peaceful harmony in a picture'] can be thought of as the result of particular kinds of construction. The same fragments of bone that lead one paleontologist to make an accurate model of an unspectacular creature might lead another, perhaps more anxious or more dramatic, to 'reconstruct' a nightmarish monster." (pp.96-97)
"To 'direct attention' to a figure is to attempt a more extensive synthesis of it. Of course, synthesis presupposes some prior analysis, as the paleontologist must have some fragments of bone before he can build his dinosaur…" (p.103)
"Recognition, whether of spelling patterns or words as wholes, must be mediated by relevant features, as meaningless in themselves as the bone chips of the paleontologist." (p.114)
"The process of figural synthesis does not depend only on the features extracted from the input, just as the dinosaur constructed by a paleontologist is not based only on the bone chips he has found. Equally important is the kind of perceptual object the perceiver is prepared to construct. The importance of set and context on the perception of words has been demonstrated in a great many experiments." (pp.115-116)
Neisser, 1967
And as with perception, so memory…
When Neisser discusses memory he uses a kind of double analogy – suggesting that memory is a bit like perception, which (as already established) is a bit like the work of the palaeontologist:
"Perception is constructive, but the input information often plays the largest single role in determining the constructive process. A very similar role, it seems to me, is played by the aggregate of information stored in long-term memory.
This is not to say that the stimuli themselves are copied and stored; far from it. The analogy being offered asserts only that the role which stored information plays in recall is like the role which stimulus information plays in perception….The model of the paleontologist, which was applied to perception and focal attention in Chapter 4, applies also to memory: out of a few stored bone chips, we remember a dinosaur….one does not recall objects or responses simply because traces of them exist in the mind, but after an elaborate process of reconstruction, (which usually makes use of relevant stored information).
What is the information – the bone chips – on which reconstruction is based? The only plausible possibility is that it consists of traces of prior processes of construction. There are no stored copies of finished mental events, like images or sentences, but only traces of earlier constructive activity."
Neisser, 1967, p.285
Fleshing-out the metaphor
Neisser then pushes the analogy one step further, by pointing out that the 'fleshed-out' model of a dinosaur in the museum may be constructed in part based on the fossil fragments of bones, but those fragments themselves do not form part of the construction (the model). The bones are used as referents in building the skeletal framework (literally, the skeleton) around which the model will be built, but the model is made from other materials (wood, steel, fibreglass, whatever) and the fossil fragments themselves will be displayed separately or perhaps filed away in a drawer in the museum archives. (As in the representational redescription model – the original representation is redescribed at another level of the system.)
"The present proposal is, therefore, that we store traces of earlier cognitive acts, not of the products of those acts. The traces are not simply 'revised' or 'reactivated' in recall; instead, the stored fragments are used as information to support a new construction. It is as if the bone fragments used by the paleontologist did not appear in the model he builds at all – as indeed they need not, if it to represent a fully fleshed-out skin-covered dinosaur. The bones can be thought of, somewhat loosely, as remnants of the structure which created and supported the original dinosaur, and thus as sources of information about how to reconstruct it."
A final reference to the analogy is used when Neisser addresses the question of the cognitive executive: the notion that somewhere in the cognitive system there is something akin to an overseer who direct operations:
"Who does the turning, the trying, and the erring" Is there a little man in the head, a homonculus, who acts the part of the paleontologist vis-à-vis the dinosaur? p.293
Neisser, 1967, p.293
The homonculus can be pictured as a small person sitting in the brain's control room, for example, viewing the images being projected from the visual input.
It is usually considered this is a flawed model (potentially lading to an infinite regress), a failure to take a systemic view of the cognitive system. It is the system which functions and leads to our conscious experience of perceiving, attending, making decisions, planning, remembering, and so forth. Whilst there are specialist components (modules) including for the coordination of the system, there is not a discrete controller overlaying the system as a whole who is doing the seeing, hearing, thinking, etcetera based on outputs from processing by the system.
Here the homonculus would like an authority that the palaeontologist turned to in order to decide how to build her model: raising the question of how does that expert know, and who would they, in turn, ask?
Why change Hebb's orignal analogy?
Altohugh Neisser refers to the analogy as being that used by Hebb, he modifies it. A tooth and rib become fragments of bone, and the early man becomes a dinosaur. Whether the shift from the reconstruction of an early hominid to the reconstruction of a terrible lizard was a deliberate one (for greater effect? because Neisser thought it would be more familiar to his readers?) or not I do not know. The phrasing suggests that Neisser thought he was applying Hebb's original comparison – so I suspect this is how he recalled the analogy.
Perhaps Neisser had regularly used the analogy in his teaching, in which case it may have become so familiar to him that he did not feel the need to check the original version. That is, perhaps he was correctly remembering how he had previously misremembered the original analogy. That is not fanciful, as memory researchers suggest this is something that is very common. Each time we access a memory the wider representational context becomes modified by engagement with it.
That is, if what is represented (in 'long-term memory'*) is indeed "traces of prior processes of construction…traces of earlier constructive activity" then each time a 'memory' is experienced, by being constructed based on what is represented ('in memory'*), new traces of that process of constructing the memory are left in the system.
It is possible over the years to be very convinced about the accuracy of a distorted memory that has been regularly reinforced. (The extent to which this may in part be the origin of many wars, feuds, and divorces might be a useful focus for research?)
So perhaps Neisser had represented in his long-term memory the analogy of a palaeontologist with a few fossil fragments, and when he sought to access the analogy, perhaps in a classroom presentation, the other elements were filled-in: the 'tooth and rib' became 'a few fragments of what might be bones' and the 'early man' become 'a dinosaur' – details that made sense of the analogy in terms familiar to Neisser.
The account of cognition that Hebb, Neisser and Schater were presenting would suggest that if this had been the case then for Neisser there would be no apparent distinction between the parts of Hebb's analogy that Neisser was remembering accurately, and the parts his preconscious mind had filled-in to construct a coherent analogy. I like the reflexive nature of this account – of someone reconstructing an analogy about how cognition reconstructs coherent wholes from partial, fragmented data – from a partial, fragmented memory representation.
Sources cited:
Bartlett, F. C. (1932/1995). Remembering: A study in experimental and social psychology Cambridge: Cambridge University Press.
Brown, R. E. (2020). Donald O. Hebb and the Organization of Behavior: 17 years in the writing. Molecular Brain, 13(1), 55. doi:10.1186/s13041-020-00567-8
Hebb, D. O. (1949). The Organisation of Behaviour. A neuropsychological theory. New York: John Wiley & Sons, Inc.
Karmiloff-Smith, A. (1996). Beyond Modularity: A developmental perspective on cognitive science. Cambridge, Massachusetts: MIT Press.
Neisser, U. (1967). Cognitive Psychology. New York: Appleton-Century-Crofts.
Schacter, D. L. (1995). Memory distortion: history and current status. In D. L. Schacter (Ed.), Memory Distortion. How minds, brains, and societies reconstruct the past (pp. 1-43). Cambridge, Massachusetts: Harvard University Press.
* terms like 'in memory' and 'in long-term memory' may bring to mind the folk-notion of memory as somewhere in the brain where things are stored away, whereas it is probably better to think of the brain as a somewhat plastic processing system which is constantly being modified by its own functioning. The memory we experience is simply the outcome of active processing** in part of the system that has previously been modified by earlier mental activity (** active processing which is in turn itself further modifying the system).
Unseen minerals all around us (Ockham's Razor – ABC)
I was listening to a recent episode of 'Ockhams' razor' (ABC's series of short science and technology essays) from 2020 called 'Unseen minerals all around us'. As a radio programme, the audience was likely to be diverse in terms of age, interests, and background knowledge and experiences.
The speaker was Allison Britt, Director of Mineral Resources Advice and Promotion, Geoscience Australia ("Australia's pre-eminent public sector geoscience organisation"), and she was describing the large number of elements used in constructing a modern mobile phone – apparently someone had put a phone in a laboratory blender and analysed the smoothie produced! (Please note: that is not a safe activity for a home science practical.)
Allison Britt, Director of Mineral Resources Advice & Promotion, Geoscience Australia – at a live recording of 'Okham's razor'. (Source: Twitter)
As a science teacher (well, retired – but once a science teacher, always a science teacher at heart at least) I tend to be primed to focus on the ways in which teachers and scientists 'make the unfamiliar familiar', and Britt used an analogy with multiple targets.
The source domain was something familiar from everyday life – seasoning food.
I thought this worked really well, although as a purist (and, as noted here before, something of a pedant) I would have liked the third of her comparisons to refer to a difference that was a matter of degree (e.g., 'taste better' cf. 'work more efficiently'). That said, Britt's formulation worked better as scientific poetry:
So, just like adding salt and pepper to a meal makes it taste better:
putting a little rhenium in a jet engine makes it burn faster and hotter;
putting a little scandium in an aeroplane makes it lighter and stronger;
and putting a little indium in your mobile phone makes the touchscreen work.
Britt, 2021
This was an example of a science communicator making the point of how adding a small, sometimes trace, quantity of a substance can make a substantive difference to properties. I imagine that virtually everyone listening to this would have effortlessly understood the comparison – a key criterion for an effective teaching analogy.
Dampening down COVID? (Image by Iván Tamás from Pixabay)
Analogy in science
Analogy is a common technique used in science and science education. In scientific work analogy may be used as a thinking tool useful for generating hypotheses to explore – "what if X is like Y, then that might mean…". That is, we think we understand system Y, so, if for a moment we imagine that system X may be similar, then by analogy that would mean (for example) that A may be the cause of B, or that if we increase C then we might expect D to decrease… Suggesting analogies has been used as a way of introducing a creative activity into school science (Taber, 2016).
Scientists also sometimes use analogies to explain their ideas and results to other scientists. However, analogies are especially useful in explaining abstract ideas to non-experts, so they are used in the public communication of science by comparing technical topics with more familiar, everyday ('lifeworld') phenomena. In the same way, teachers use analogies as one technique for 'making the unfamiliar familiar' by suggesting that the unfamiliar curriculum focus (the target concept to be taught) is in some ways just like a familiar lifeworld phenomena (the analogue or source concept).
So, I was interested to hear Prof. Andrew Hayward, Professor of Infectious Disease Epidemiology and Inclusion Health Research at UCL (University College London), being interviewed on the radio and suggesting that COVID was like a fire:
"Sometimes I like to think of, you know, COVID as a fire, if we are the fuel, social mixing is the oxygen that allows the fuel to burn, vaccines the water that stops the fuel from burning, and COVID cases are the sparks that spread the fire. So, we are doing well on vaccines, but there's lots of dried wood left."
There's quite a lot going on in that short statement. If Prof. Hayward had stopped at "sometimes I like to think of COVID as a fire" this would have been a simile where it is simply observed that one thing is conceived as being a bit like another.
Simile offers a comparison and leaves the listener or reader to work out the nature of the similarity (whereas metaphor, where one thing is described to be another, an example would be 'COVID is a fire', leaves the audience to even appreciate a comparison is being made). Analogy goes further, as it makes a comparison between two conceptual structures (two systems), such that by mapping across them we can understand how the structure of the unfamiliar is suggested to be like the more familiar structure.
That is, there is a mapping (see the figure below) that is based on pairings across the analogy. Here fire and COVID disease are each treated as systems with components that are structured in a parallel way:
COVID (illness): fire
people: fuel
social mixing: oxygen
vaccines: water
COVID cases: sparks
A graphic representation of Prof. Hayward's use of analogy
A lot of us are like kindling
Moreover, having set up this analogy, we are offered some additional information – we are doing well on vaccines (= there is plenty of water to stop fuel burning), but there is still a lot of dried wood. The listener has to understand that the dry wood refers to fuel, and this maps (in the analogy) onto lots of people who can still become infected.
I suspect most people (science teachers perhaps excepted) listening to this interview will not have even explicitly noticed the nature of the analogy, but rather automatically processed the comparison. They would have understood the message about COVID through the analogy, rather than having to actively analyse the analogy itself.
We can stop the sparks spreading the fire
Professor Hayward was asked about contact tracing and suggested that
"…the key thing is the human discussion with somebody who has COVID to identify who their contacts are and to ask them to isolate as well, and that really stops those sparks getting into the population and really helps to dampen down the fire."
That is, that potential COVID cases (that are like sparks in the fire system) can be prevented from mixing with the wider population (who are like fuel in the fire system) and this will dampen down the fire (the illness in the COVID system). {Note 'dampen down' seems to be a metaphor here rather than a true part of the analogy (in which it is the vaccines that have the effect of 'literally' {analogously} dampening down the fire). Stopping sparks mixing with fuel will limit new areas of combustion starting rather than dampening down the existing fire.}
An argument about contact tracing made using the analogy
Again, most people listening to this would likely have taken on board the intended meaning quite automatically, without having to deliberately analyse this answer – even though the response shifts between the target topics (the COVID disease system) and the analogue (the fire system) – so the sparks (fire system – equivalent to infectious cases) are stopped from getting into the population (COVID system – equivalent to the fuel supply).
This is reminiscent of chemistry teaching which slips back and forth between macroscopic and molecular levels of description – and so where references to, for example, hydrogen could mean the substance or the molecule – and the same word may have a different referent at different points in the same utterance (Taber, 2013). Whether this is problematic depends upon the past experiences of the listener – someone with extensive experience of a domain (probably most of the audience of a serious news magazine programme understand enough about combustion and infection to not have to deliberate on the analogy discussed here) can usually make these shifts automatically without getting confused.
Fire requires…AND…AND…
An analogy can only be effective when the analogue is indeed more familiar to the audience (you cannot make the unfamiliar familiar by comparing an unfamiliar target with an analogue that is also unfamiliar) so the use of the analogy by Professor Hayward assumed some basic knowledge about fire. Indeed it seemed to assume knowledge of the so-called 'fire triangle'.
Three factors are need to initiate/maintain combustion: fire may be stopped by removing one or more of these.
This is the idea that for a fire to commence or continue there need to be three things: something combustible to act as fuel; AND oxygen (or another suitable substance – as when iron filings burn in chlorine – but in usual circumstances it will be oxygen); AND a source of energy sufficient to initiate reaction (as burning is exothermic, once a fire is underway it may generate enough heat to maintain combustion – and sparks may spread the fire to nearby combustible material). To extinguish a fire, one needs to remove at least one of these factors – water can act as a heat sink to decrease the temperature, and may also reduce the contact between the fuel and oxygen. Preventing sparks from transferring hot material that can initiate further sites of combustion (providing energy to more fuel) can also be important.
Unobtrusive pedagogy
The quotes here were part of a short interview with a broadcast journalist and intended for a general public audience. Prof. Hayward introduced and developed his analogy as just sharing a way of thinking, and indeed analogy is such a common device in conversation that it was not obviously marked as a pedagogic technique. However, when we think about how such a device works, and what is expected of the audience to make sense of it, I think it is quite impressive how we can often 'decode' and understand such comparisons without any conscious effort. Providing, of course, that the analogue is indeed familiar, and the mapping across the two conceptual structures can be seen to fit.
Analogies can be used as pedagogic devices to make the unfamiliar familiar' – that is by suggesting that something (the unfamiliar thing being explained) is somehow like something else (that is already familiar), the unfamiliar can start to become familiar. The analogy functions like a bridge between the known and the unknown. (Note: the idea of a bridge is being used as simile there – another device that can be used to help make the unfamiliar familiar.)
For an analogy (or simile) to work, the person being taught or communicated with has to already be familiar with the 'source' that act as an analogue for the 'target' being communicated. (If someone did not know what a bridge was, what it is used for, then it would be no help to them to be told that an analogy can function like one! Indeed it would probably just confuse matters.)
An analogy is based on some mapping of structure between two different systems. For example, at one time a common teaching analogy was that the atom was like a tiny solar system. For that to be useful to a learner, they would need to be more familiar with the solar system than the atom. To be used as an effective teaching analogy, the learner would have to understand the relevant parts of the conceptual structure of the solar system idea that were being mapped across to the atom (perhaps a relatively large central mass, the idea of a number of less massive bodies orbiting in some way, a force between the central and peripheral bodies responsible for the centripetal acceleration of the orbiting bodies…).
A person might easily map across irrelevant aspects of the source to the target, perhaps as all the planets are different then all electrons must be different! This might explain why some students assume the force holding the atom together is gravitational!
In teaching science, it is common to use everyday sources as analogues for scientific ideas. But, of course, it is also possible to use scientific ideas as the source to try to explain other target ideas.
Provides alternative reaction pathway with small energy barriers
Structures learning by modelling activity, and leads learner through small manageable steps
Matching
The enzyme 'fits' the reactant molecule and readily binds
A good scaffold matches the learners' current capacity to progress in learning (in the so-called 'ZPD')
Degrees of freedom
The binding of the enzyme to a substrate 'guides' the subsequent molecular reconfiguration
The scaffolding guides the steps in the learning process taken by the learner
Mapping between two analogous conceptual structures
Scaffolding Learning as Akin to Enzymatic Catalysis
"Metaphors and analogies should always be considered critically, as the aspects that do not map onto the target they are being used to illustrate can often be as salient and as relevant as the aspects that map positively. Given that, and in the spirit of offering a way to imagine scaffolding (rather than an objective description) we suggest it may be useful to think of scaffolding learning as like the enzymatic catalysis of a chemical process in the body (see Figure 3).
Figure 3. Scaffolding learning can be seen as analogous to enzymatic catalysis (b) which facilitates a reaction with a substantive energy barrier (a).
Some chemical reactions are energetically viable (in chemical terms, exothermic) and so in thermodynamic terms, occur spontaneously. However, sometimes even theoretically viable (so spontaneous) reactions occur at such a slow rate that for all practical purposes there is no reaction. For example, imagine a wooden dining table in a room at 293 K (20˚C) with an atmosphere containing about 21% oxygen – a situation found in many people's homes. The combustion of the table is a viable chemical process [1] and indeed the wood will (theoretically) spontaneously burn in the air. Yet, of course, that does not actually happen. Despite being a thermodynamically viable process, the rate is so slow that an observer would die of old age long before seeing the table burst into flames, unless some external agent actively initiated the process. If parents returned home from an evening out to be told by their teenage children that the smouldering dining table caught alight spontaneously, the parents would be advised to suspect that actually this was not strictly true. Although the process would be energetically favourable, there is a large energy barrier to its initiation (cf. Figure 3, top image). Should sufficient energy be provided to ignite the table, then it is likely to continue to burn vigorously, but without such 'initiation energy' it would be inert.
The process of catalysis allows reactions which are energetically favourable, but which would normally occur at a slow or even negligible (and in the case of our wooden table, effectively zero) rate to occur much more quickly – by offering a new reaction pathway that has a much lower energy barrier (such that this is more readily breached by the normal distribution of particles at the ambient temperature).
In living organisms, a class of catalysts known as enzymes, catalyse reactions. Enzymes tend to be specific to particular reactions and very effective catalysts, so reactions akin to the burning of organic materials (as found in our wooden table) can occur as part of metabolism at body temperature. The second image in Figure 3 represents the same chemical reaction as in the top image (note the same start and finish points) reflecting how an enzyme changes the reaction pathway, but not the overall reaction. Two particular features of this graphical metaphor are that the overall process is broken down into a number of discrete steps, and the 'initiation energy' needed to get the process underway is very much smaller.
This is similar to the mediation of learning trough scaffolding, where a task that is currently beyond the capacity of the learner is broken down into a sequence of smaller steps, more manageable 'learning quanta', and the learner is guided along a learning pathway. The parallels go beyond this. Part of the way that an enzyme functions is that the enzyme molecule's shape is extremely well matched to bind to a target reactant molecule (something reflected in the teaching analogy of the 'lock and key' mechanism of enzymatic action: the enzyme and substrate molecules are said to fit together like a lock and key). This is analogous to how effective scaffolding requires a teacher to design a scaffold that fits the learner's current level of development: that is, her current thinking and skills. Once the substrate molecule is bound to the enzyme molecule, this then triggers a specific reconfiguration: just as a good scaffolding tool suggests to the learner a particular perspective on the subject matter.
Moreover, whereas a free substrate molecule could potentially follow a good many different pathways, once it is bound to the enzyme molecule its 'degrees of freedom' are reduced, so there are then significant constraints on which potential changes are still viable. Most organic chemistry carried out in vitro (in laboratory glassware) is inefficient as there are often many 'side reactions' that lead to unintended products, just as students may readily take away very different interpretations from the same teaching, so the yield of desired product can be low. However in vivo reactions (in living cells), being enzyme-catalysed, tend to give high yields.
The process of enzymatic catalysis therefore makes the preferred pathway much 'easier', offers a guide along the intended route, and channels change to rule out alternative pathways. Digital tools that support teaching to meet curricular aims, such as apps intended to be used by learners to support study, therefore need to offer similar affordances (structuring student learning) and constraints (reducing the degrees of freedom to go 'off track'). Clearly this will rely on design features built into the tool. Here we very briefly discuss two examples."
[1] We avoid the term 'reaction' here, as strictly a chemical reaction occurs between specific substances. Wood is a material composed of a wide range of different compounds, and so the combustion of wood is a process encompassing a medley of concurrent reactions.
Cause and effect?: People go to different places because of what they are wearing
Keith S. Taber
Image by anwo00 from Pixabay
Annie was a participant in the Understanding Chemical Bonding project. She was a second year 'A level' student (c.18 years of age) when she was talking to me about atoms and electrons, but I was struck with the way she used the word 'because'.
Technically this conjunction is linked with causality, something of importance in science. To say that X occurred because of Y is to claim that Y was a cause of X.
I wanted to clarify if Annie's use of 'because' in that chemical context actually implied that she was describing what she considered a cause, or whether she was using the word more loosely. To probe this I presented what I considered an obviously inappropriate use of 'because': that football fans following different teams in the same city would go to different matches BECAUSE of the colour of the clothes they wore (i.e., hats and scarves traditionally worn to show support to a particular team).
Because the sky is blue, it makes me cry
I expected Annie to point out that this was not the reason, and so 'because' should not be used – which would have then allowed me to return to her earlier use of 'because' in the context of atoms. However, Annie seemed quite happy with my supposedly 'straw-man' or 'Aunt Sally' example:
So we're talking about what you might call cause and effect, that something is caused by something else. We do a lot of talking about cause and effect in science – "this causes that to happen."
If you think about people in Liverpool, only because this is the first analogy that comes to mind, if you actually go to Liverpool on Saturday [*] and wander round, you'll probably find quite a few people wandering around wearing red, and quite a few people wandering around wearing blue, and sometime after lunch you'll find that all the people wearing red, a lot of the people wearing red, tend to move off to one particular place.[**] And the people wearing blue tend to move to a different sort of place, as though they are repelled, you know, similar colours attracted together.
Uh hm.
Agreed?
Yes.
And we could say therefore, that the reason that some people go towards the Liverpool ground, is because they're wearing red, and the reason some people go towards the Everton ground, is because they're wearing blue. Now would that be a fair description?
Yeah.
And do you agree with the sense of cause and effect there – that people go to watch Liverpool because they're wearing red hats and red scarves? And people go to look at Everton because they're wearing blue hats and blue scarves?
Yes.
So would you say the cause of which football team you go to see, the cause of that, is what clothes you happen to be wearing?
(Pause, c.4s)
Unless you're a rambler. {Laughs}…
No, no, well yes, if you're wearing, you're obviously supporting that colour, so, that team, so so you'd assume, that they were going to watch, the team they favoured.
Right, okay, erm, I'll think of a different example, I think.
Because the world is round, it turns me on
Annie did not seem to 'get' what I had thought would be an obvious flaw in the argument. Fans wear the colours of their team to show support and affiliation; and go to the place where their team is playing: but they do not go to the particular stadium because they happen to be wearing red or blue.
This is linked to the difference between causation and correlation. Often two correlated variables do not have a direct causal relationship, but have a relationship mediated by some other factor.
Height of children in a primary school will be correlated with their grade number (on average, the children in the first year are shorter than those in the second year, who are shorter than…). But children are not organised into grades according to height, and height is not caused by grade. Both are independently related to the child's age.
Colour of football scarves is correlated with destination on match day, but one does not cause the other – rather both colour choice and destination are actually due to something else: affiliation to a club. [***]
I switched to a another example I hoped would be familiar, based on a swimming pool. I though the idea that changing rooms are (usually) designated by gender would make it obvious that where people went to change on leaving the pool correlated to, but was not because of, what they were wearing. Again, however, Annie did not seem to consider it inappropriate to describe this in terms of the the different types of swimming costume causing the behaviour.
If you go to the swimming pool, and watch people swimming, you'll find out that some people when they're swimming at a swimming pool, tend to wear a swimming costume that only covers, the hips basically, and other people either a swimming costume that covers most of the trunk, or two separate parts to it. And if you observe them very closely, which is always a bit suspicious at a swimming pool, you'll notice that when they get out of the pool, they're attracted towards different rooms, these changing rooms…
But all the people who just have the one part of the costume, are attracted towards one room, and the others are attracted towards the other room, the ones with sort of either very long costumes or two part costumes. So is it fair to say that it's caused by what clothes they are wearing, that determines which room they go and get changed in?
Yes.
It is?
(Pause, c.4s)
Yes.
That's the cause of it?
(Pause, c5s)
Yeah. It's also conventional as well.
So in both cases Annie was happy to talk in terms of the clothing causing behaviour. After some further discussion Annie seemed to appreciate the distinction I was making, but even if she did not have a flawed notion of causality, it certainly appeared she have developed non-canonical ways of talking about cause and effect.
Because the wind is high, it blows my mind
Annie was a clever person, and I am sure that the issue here was primarily about use of language rather than an inability to understand causation. However, even if our thinking is not entirely verbal, the major role of verbal language in human thought means that when one does not have the language, one may not have the related explicit concepts.
It is very easy to assume that students, especially those we recognise as capable and having been academically successful, share common 'non-technical' language – but there is plenty of research that suggests that many students do not have a clear appreciation of how such terms are canonically used. These are terms we might think people generally would know, such as adjacent, efficient, maximum, initial, omit, abundant, proportion… (Johnstone & Selepeng, 2001). As always, a useful guide to the teacher is 'never assume'.
* At the time of the interview, it was general practice for most English football league matches to be played at 15.00 on a Saturday.
** One constraint on the scheduling of football matches is that, as far as possible, two local rival ('paired') teams should not play home matches on the same day, to avoid potential clashes between large crowds of rival fans. However, such 'paired clashes', as they are technically called (Kendall et al., 2013), are not always avoided.
*** Of course, this is not a direct cause. A person could support one team, yet choose to wear the colours of another for some reason, but their support for a team usually motivates the choice. Social patterns are messier than natural laws.
Sources cited:
Johnstone, A. H., & Selepeng, D. (2001). A language problem revisited. Chemistry Education: Research & Practice in Europe, 2(1), 19-29.
Kendall G., McCollum B., Cruz F.R.B., McMullan P., While L. (2013) Scheduling English Football Fixtures: Consideration of Two Conflicting Objectives. In: Talbi EG. (eds) Hybrid Metaheuristics. Studies in Computational Intelligence, vol 434. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-30671-6_14
I've just seen* an article in Chemistry: Bulgarian Journal of Science Education describing how students intending to be teachers were introduced to ideas about intermolecular bonding by analogy with attraction between people (Karakaş, 2012). In this analogy nuclei are seen as female and electrons as male, and so sometimes the electrons may take an interest in nuclei other than their own, so to speak: hydrogen bonding is seen as a "form of dipole-dipole interactions, caused by highly electronegative atoms (caused by couples with highly attractive females)", occurring between hydrogen and
"oxygen (couple where the nucleus is Maria Sharapova), fluorine (couple where the nucleus is Kim Kardashian) or nitrogen (couple where the nucleus is Beyonce)" (p.345).
This seems to be a variation on an approach that has been around at least since I started teaching (I remember comparing displacement reactions to interactions between couples at parties), and is clearly meant to be a fun idea, as well as having a motivation in terms of making abstract chemical ideas relevant by comparison with something familiar. The study reported was undertaken in Turkey, and I wondered about the cultural acceptability of this approach these days in different contexts. So Karakaş reports that
"the instructor said in a patriarchal society such as Turkey, the male is supposed to take care of the female. Then the instructor said that basically, the male has to revolve around the female like an electron revolving around a nucleus" (p.343).
I suspect that in many countries it might be considered quite inappropriate to make such a comment about gender roles, at least not without a clear sense of intended satire. More significantly, I wonder how acceptable it is to talk about the relative sexual attractiveness of different people – is that politically correct? Especially if the idea was used with adolescent students, many of whom may well be suffering issues relating to their perceptions of their own attractiveness.
Finally, of course, the basic premise, that sexual orientation matches the principle found with electrical charge – opposite charges attract, similar charges repel – would certainly be suspect in the context where I work (where a current issue of public debate is whether same sex couples should be allowed to marry rather than just register civil partnerships). In some ways these complications are a shame, as the analogy will be seen as fun by many learners, and it certainly is something most learners will relate to. This example reminds us that even if chemistry itself can be seen as largely culture-free, teaching and learning of science always takes place in a cultural context that also influences what can be considered good teaching.
Reference: Karakaş, M. (2012). Teaching Intermolecular Forces with Love Analogy: A Case Study. Chemistry: Bulgarian Journal of Science Education, 21(3), 341-348.
* Previously published at http://people.ds.cam.ac.uk/kst24/science-education-research: 9th May 2015
Amy (Y10) suggested that a circuit was "a thing containing wires and components which electricity can pass through…it has to contain a battery as well". She thought that electricity could pass through "most things".
For Amy "resistance is anything which kind of provides a barrier that, which the current has to pass through, slowing down the current in a circuit", and she thought about this in terms of the analogy with water in pipes: "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 at one point, erm, the water flow has to slow down, and that's meant to represent the resistance of something".
So for Amy, charge flow was impeded by physical barriers effectively blocking its way. She made the logical association with the density of a material, on the basis that a material with densely packed particles would have limited space for the charge to flow:
So electricity would "not very easily" pass through a wooden bench "because wood is quite a dense material and the particles in it are quite closely bonded".
In air, however, the particles were "not as dense as a solid". When asked if that meant that electricity can pass through air quite easily, Amy replied: "yeah, I think so".
Amy's connection between the density of particles and the ease with which charge could flow is a logical one, but unfortunately involves a misunderstanding of how charge flows through materials, i.e., from a canonical scientific perspective, thinking about the charge flowing through gaps between particles is unhelpful here. (So this can be considered an alternative conception.) This seems to be a creative associative learning impediment, where prior learning (here, the spacing of quanticles in different materials) is applied, but in a context beyond its range of application.
Amy was a participant in the Understanding Science project. She was interviewed when she had just started her 'A level' (i.e., college) chemistry, and one of the topics that the course had started with was mass spectrometry. She gave me a very detailed account of what she had been taught, despite both casting doubt on the logic of parts of the account, and of the accuracy of her own recollection (see Amy's account of mass spectrometry *). One of the unconvincing aspects of the new topic seemed to be the way positive ions were produced by bombarding atoms with (negative) electrons – although she had clearly picked up the point.
She reported that her teacher had demonstrated this point with an analogy. She told me that the teacher was using a lot of analogies, and she seemed to find them a little silly, implying that this analogy was not helpful. This particular example involved a board duster and two matchboxes. One matchbox sat on the duster, and was knocked off by the other matchbox being projected at it.
I thought this was quite interesting, as Amy did think the formation of positive ions was counter-intuitive, but had remembered that this is what happened, and seemed to both remember and understand the use of the analogy – even though she was somewhat dismissive of it. I didn't get the chance to explore the issue at the time, but wondered if this was an example of a student maybe not appreciating the role of models and analogies (and simulation) in science itself, and so feeling that using such a device in teaching science was a little 'naff'.
Amy's explanation of the stupid-sounding bit
Amy was dismissive of the teacher's analogical teaching model, even though she seemed to have remembered what he was illustrating:
I mean there was a couple of bits there that you didn't seem too sure about like, like er you know you sort of, you seemed to almost disown the fact that this electron gun is going to make these things into positive ions, you didn't seem very convinced by that?
Erm – I dunno if it's that I'm not convinced it just sounds weird, because it's like erm (pause, c.2s) I dunno, well it's like it's not something which you can see,
No.
and it's like, I dunno, he did this sort of example using a duster and two matchboxes, and, which wasn't very good, so.(Amy was laughing at this point)
Tell me about that then, how does that work? You see I know a bit about this, I don't know about the duster and the matchboxes.
Like no disrespect to our teacher but he uses these analogies, a duster being an atom with matchboxes being the electrons and something, and them being knocked off, because, yeah.
So he threw a matchbox at a duster that had a matchbox and he knocked the matchbox off the duster?
Pretty much.
See, it works for me,
(Amy laughs)
and you've remembered it?
Well, yeah, but – yeah.
…
Erm, So you've got this neutral atom, and you're firing negative electrons at it?
Yeah.
Now if you say that to somebody who doesn't know anything about what's going to happen, what do you think might happen if you fire negative electrons at a neutral atom?, what might you get?
A negative ion.
That's what you'd expect I think, isn't it, … well obviously you are firing negative things at it, so you will get negative. But in fact that's not what seems to happen. So he was trying to explain to you why firing negative things, at something neutral, you might end up with something positive. 'cause that's not obvious and logical, is it?
Yeah.
So if you throw a matchbox at a duster that contains a matchbox, you might knock the match box off?
Yeah (Amy laughs).
There is clearly a 'cultural' difference here, between the interviewer (a science teacher by background) and the interviewee (the learner), in that the interviewer 'got' the use of the demonstration as a pretty neat physical analogy, whereas the student clearly was dismissive. In this case Amy's lack of engagement with the modelling process did not seem to limit her learning, but her attitude demonstrated a lack of awareness of the status and roles of models in science (and in learning science) which has potential to act as a deficiency learning impediment if she cannot see how teaching models and analogies can help form mental models of scientific systems.
