confusing levels - Science-Education-Research

My brain can multitask even if yours makes a category error

Do not mind the brain, it is just doing its jobs

Keith S. Taber

Can Prof. Dux's brain really not multitask?

I was listening to a podcast where Professor Paul Dux of the University of Queensland said something that seemed to me to be clearly incorrect – even though I think I fully appreciated his point.

"why the brain can't multitask is still very much a topic of considerable debate"
Prof. Paul Dux

Is it true that brains cannot multitask? I think mine can. (Image by Gerd Altmann from Pixabay)

The podcast was an episode of the ABC radio programme All in the Mind (not to be confused with the BBC radio programme All in the Mind, of course) entitled 'Misadventures in multitasking'

"All in the Mind is an exploration of the mental: the mind, brain and behaviour — everything from addiction to artificial intelligence." An ABC radio programme and podcast.

The argument against multitasking

Now mutlitasking is doing several things at once – such as perhaps having a phone conversation whilst reading an unrelated email. Some aspects of the modern world seem to encourage this – such as being queued on the telephone (as when I was kept on hold for over an hour waiting to get an appointment at my doctor's surgery – I was not going to just sit by the phone in the hope I would eventually get to the top of the queue). Similarly 'notifications' that seek to distract us from what we are doing on the computer, as if anything that arrives is likely to be important enough for us to need immediate alerting, add little to the sum of human happiness.¹

Now I have heard the argument against multitasking before. The key is attention. We may think we are doing several things at once, but instead of focusing on one activity, completing, it, then shifting to another, what multitaskers actually do is continuously interrupt their focus on one activity to refocus attention on the another. The working memory has limited capacity (this surely is what limits our ability to reflectively multitask?), and we can only actually focus on one activity at a time, so multitasking is a con – we may think we are being more productive but we are not.

Now, people do tire, and after, say 45 minutes at one task it may be more effective to break, do something unrelated, and come back to your work fresh. If you are writing, and you break, and take the washing out of the machine and hang it up to dry, and make a cup of tea, and then come back to your writing fifteen or twenty minutes later, this is likely to be ultimately more productive than just ploughing on. You have been busy, not just resting, but a very different kind of activity, and your mind (hopefully) is refreshed. If you have been at your desk for 90 minutes without a break, then go for a walk, or even a quick lie down.

That however, is very different from doing your writing, as you check your email inbox, and keep an eye on a social media feed, and shop online. You can only really do one of those things at a time and if you try to multitask you are likely to quickly tire, and make mistakes as you keep interrupting your flow of concentration. (So, if you have been doing your writing, and you feel the need to do something else, give yourself a definite period of time to completely change activity, and then return fully committed to the writing.)

Now, I find that line of argument very convincing and in keeping my with own experience. (Which is not to say I always follow my own advice, of course.) Yet, I still thought Prof. Dux was wrong. And, indeed, there is one sense in which I would like to think deliberate reflective multitasking is not counterproductive.

If your brain cannot multitask you'd perhaps better hope it focuses on breathing

The brain is complex…

This is a short extract from the programme,

Paul Dux: Why the brain can't multitask is still very much a topic of considerable debate because we have these billions of neurons, trillions of synaptic connections, so why can't we do two simple things at once?
Sana Qadar: This is Professor Paul Dux, he's a psychologist and neuroscientist at the University of Queensland. He takes us deeper into what's going on in the brain.
Paul Dux: A lot of people would say it's because we have these capacities for attention. The brain regions that are involved in things like attention are our lateral prefrontal cortex. You have these populations of neurons that respond to lots of different tasks and multiple demands. That of course on one hand could be quite beneficial because it means that we are able to learn things quickly and can generalise quickly, but maybe the cost of that is that if we are doing two things at once in close temporal proximity, they try to draw on the same populations of neurons, and as a result leads to interference. And so that's why we get multitasking costs.
Sana Qadar: Right, so that's why if you are doing dishes while chatting to a friend, a dish might end up in the fridge rather than the cupboard where it's supposed to go.
Paul Dux: That's right, exactly.
Paul Dux talking to Sana Qadar who introduces 'All in the mind'

Now I imagine that Prof. Dux is an expert, and he certainly seemed authoritative. Yet, I sensed a kind of concept-creep, that led to a category error, here.

A category error

A category error is where something is thought of or discussed as though a member of an inappropriate class or category. A common example might be gender and sex. At one time it was widely assumed that gender (feminine-masculine) was directly correlated to biological sex (female-male) so terms were interchangeable. It is common to see studies in the literature which have looked for 'sex differences' when it seems likely that the researchers have collected no data on biological sex.

Models that suggest that the 'particles' (molecules, ions, atom) in a solid are touching encourage category errors among learners: that such quanticles are like tiny marbles that have a definite surface and diameter. This leads to questions such as whether on expansion the particles get larger or just further apart. (Usually the student is expected to think that the particles get further apart, but it is logically more sensible to say they get larger. But neither answer is really satisfactory.)

If someone suggested that a mushroom must photosynthesise because that is how plants power their metabolism then they would have made a category error. (Yes, plants photosynthesise. However, a mushroom is not a plant but a fungus, and fungi are decomposers.)

The issue here, to my mind (so to speak) was the distinction between brain (a material object) and conscious mind (the locus of subjective experience). Whilst it is usually assumed that mind and brain are related (and that mind may arise, emerge from processes in the brain) they may be considered to relate to different levels of description. So, mind and brain are not just different terms for the same thing.

Mind might well arise from brain, but it is not the same kind of thing. So, perhaps the notion of 'tasks' applies to minds, not brains? (Figure from Taber, 2013)

So, it is one thing to claim that the mind can only be actively engaged in one task at a time, but that is not equivalent to suggesting this is true of the brain that gives rise to that mind.²

Prof. Dax seemed to be concerned with the brain:

"the brain…billions of neurons, trillions of synaptic connections… brain regions…lateral prefrontal cortex…populations of neurons"

Yet it seems completely unfounded to claim that human brains do not multitask as we surely know they do. Our brains are simultaneously processing information from our eyes, our ears, our skin, our muscles, etc. This is not some kind of serial process with the brain shifting from one focus to another, but is parallel processing, with different modules doing different things at the same time. Certainly, we cannot give conscious attention to all these inputs at once, so the brain is filtering and prioritising which signals are worth notifying to head office (so to speak). We are not aware of most of this activity – but then that is generally the case with our brains.

The brain controls the endocrine system. The brain stem has various functions, including regulating breathing and heart rate and balance. If the brain cannot multitask we had perhaps better hope it focuses on breathing, although even then I doubt we would survive for long based on that activity alone.

Like the proverbial iceberg, most of our brain activity takes place below the waterline, out of conscious awareness. This is not just the physiological regulation – but a lot of the cognitive processing. So, we consolidate memories and develop intuitions and have sudden insights because our brains are constantly (but preconsciously) processing new data in the light of structures constructed through past experience.

If you are reading, you may suddenly notice that the room has become cold, or that the doorbell is ringing. This is because although you were reading (courtesy of your brain), your brain was also monitoring various aspects of the environment to keep alert for a cue to change activity. You (as in a conscious person, a mind if you like) may not be able to do two things at once, so your reading is interrupted by the door bell, but only because your brain was processing sensory information in the background whilst it was also tracking the lines of text in your book, and interpreting the symbols on the page, and recalling relevant information to provide context (how that term was defined, what the author claimed she was going to demonstrate at the start of the chapter…). Your mind as the locus of your conscious experience cannot multi-task, certainly, and certainly "brain regions that are involved in…attention" are very relevant to that, but your brain itself is still a master of multitasking.

Me, mybrain, and I

So, if the brain can clearly multitask, can we say that the person cannot multitask?

That does not seem to work either. The person can thermoregulate, digest food, grow hair and nails, blink to moisten the eye etc., etc as they take an examination or watch a film. These are automatic functions. So, might we say that it is the body, not the person carrying out those physiological functions? (The body of the person, but not the person, that is.)

Yet, most people (i.e., persons) can hold a conversation as they walk along, and still manage to duck under an obstruction. The conversation requires our direct attention, but walking and swerving seem to be things which we can do on 'autopilot' even if not automatic like our heartbeat. But if there was a complex obstruction which required planning to get around, then the conversation would likely pause.

So, it is not the brain, the body, or even the person that cannot multitask, but more the focus of attention, the stream of consciousness, the conscious mind. Perhaps confusion slips in because these distinctions do not seem absolute as our [sic] sense of identify and embodiment can shift. I kick out (with my leg), but it is my leg which hurts, and perhaps my brain that is telling me it is hurting?

Figure by by mohamed Hassan from Pixabay; background by by Sad93 from Pixabay

Meanwhile, my other brain was relaxing

There is also one sense in which I regularly multitask. I listen to music a lot. This includes, usually, when I am reading. And, usually, when I am writing. I like to think I can listen to music and work. (But Prof. Dux may suggest this is just another example of how humans "are not actually good at knowing our own limitations".)

I like to think it usually helps. I also know this is not indiscriminate. If I am doing serious reading I do not play music with lyrics as that may distract me from my reading. But sometimes when I am writing I will listen to songs (and, unfortunately for anyone in earshot, may even find I am singing along). I also know that for some activities I need to have familiar music and not listen to something new if the music is to support rather than disturb my activity.

Perhaps I am kidding myself, and am actually shifting back and forth between

being distracted from my work by my music

and

focusing on my work and ignoring the music.

I know that certainly sometimes is the case, but my impression is that usually I am aware of the music at a level that does not interfere with my work, and sometimes the music both seems to screen out extraneous noise and even provides a sense of flow and rhythm to my thinking.

The human brain has two somewhat self-contained, but connected, hemispheres. (Image by Gerd Altmann from Pixabay)

I suspect this has something to do with brain lateralisation and how, in a sense, we all have two brains (as the hemispheres are to some extent autonomous). Perhaps one of my hemispheres is quietly (sic) enjoying my music whilst the other is studiously working. I even fancy that my less verbal hemisphere is being kept on side by being fed music and so does not get bored (and so perhaps instigate a distracting daydream) whilst it waits for the other me, its conjoined twin, to finish reading or writing.

I may well be completely wrong about that.

Perhaps I am just as hopeless at multitasking with my propensity to attempt simultaneous scholarship and music appreciation as those people who think they can monitor social media whilst effectively studying.³ Perhaps it is just an excuse to listen to music when I should be working.

But even if that is so, I am confident my brain can multitask, even if I cannot.

Work cited:

Taber, K. S. (2013). Modelling Learners and Learning in Science Education: Developing representations of concepts, conceptual structure and conceptual change to inform teaching and research. Dordrecht: Springer.

Note:

¹The four minute warning, perhaps. But,

Apple are releasing a new iPhone next spring?
Another email has arrived inviting me to talk at some medical conference on a specialism I cannot even pronounce?
A fiend of a friend of a friend has posted some update on social media that I can put into Google translate if I can be bothered?
Someone I do not recall seems to have a job anniversary?
Someone somewhere seems to have read something I once wrote (and I can find out who and where for a fee)?

Luckily I have been notified immediately as now I know this I will obviously no longer wish to complete the activity I was in the middle of.

² One could argue that when a person is conscious (be that awake, or dreaming) one task the brain is carrying out is supporting that conscious experience. So, anything else a brain of a conscious person is doing must be an additional task. Perhaps, the problem is that minds carry out tasks (which suggests an awareness of purpose), but brains are just actively processing?

³ As a sporting analogy for the contrast I am implying here, there is a tradition in England of attending international cricket matches, and listening to the 'test match special' commentary (i.e., verbal) on the radio while watching (i.e. visual) the match. This seems to offer complementary enhancement of the experience. But I have also often seen paying spectators on televised football matches looking at their mobile phones rather than watching the match.

In a molecule, the electron actually slots into spaces

Keith S. Taber

Mohammed was a participant in the Understanding Science Project. When interviewed in the first term of his upper secondary (GCSE) science course (in Y10), he told me he had been learning about ionic bonding in one of his science classes. Mohammed had quite a clear idea about ionic bonding, which he described in terms of the interactions of two atoms where "they both want to get full outer shells", leading to salt which was "like two atoms joined together":

The "two atoms joined together" sounds much like a molecule (and it is very common for students to identify molecule like ion-pairs even in representations of extensive ionic lattices), so I asked Mohammed about this:

Can I see these atoms?
No. They're really small. Because the wavelength of visible light is actually too like large to see the atoms, they just pass over them.
Okay, so I can't see them. But I can imagine them, can I?
Yeah.
So if I could imagine a sodium atom and chlorine atom, and then they form salt, what would it look like afterwards? How could I imagine it afterwards.
Oh it's like two atoms joined together.
That sounds like a molecule to me?
It's not actually, like, joined.
No?
Because I know that whenever things of opposite charge, I know two rods, when they come together, they don't actually touch, so they don't exactly touch, but they are very close, two atoms close to each other
So a molecule would be different to that in some way, would it?
Yeah, a molecule's actually bonded
So how that different?
I think in a molecule, the electron actually slots into spaces.
I see, and it doesn't do that in this case?
No.

So Mohammed thinks that the interaction between the ions will be due to their electrical charges, but, for him, this may not count as a bond, as the forces just hold the ions ("atoms") close together, and do not actually join them. Mohammed's idea of the atoms not actually touching, "they don't actually touch, so they don't exactly touch", is transferring a notion from the familiar world of macroscopic phenomena (where things touch, or they do not touch) to the submicroscopic world of quanticles that do not have definitive size/volume, and do not actually have distinct surfaces, so touching is a matter of degree. There is no more (or less) 'touching' in a covalent bond than in ionic bonding. So according to Mohammed the ions do not form a molecule, as in a molecule there would some kind of more direct joining – he suggests something like an interlocking with electrons from one atom slotting into spaces on another.

Interestingly, Mohammed bases his notion that the ions would not touch on a general principle that he considers to apply whenever considering things of opposite charge – which he justifies on his knowledge that "two [charged] rods, when they come together, they don't actually touch". He may be misremembering something here – or he may have seen a demonstration of suspended charged rods of the same material (so either both negatively or both positively changed) that when one is moved closer to the other the rods repel. Whatever the source, Mohammed seems to feel he has a valid general principle that he can apply here that act as a grounded learning impediment channelling his thinking about the case under discussion along 'the wrong lines'.

Mohammed's notion of the ionic bonding as being just due to forces rather than being a proper bond is very similar to a common alternative conceptions of ionic bonding which sees ions in a lattice only having a limited number of ionic bonds depending upon valency (the valency conjecture) but bonded with other coordination counter-ions by 'just forces' (the just forces conjecture) – although here Mohammed suspected that all ionic bonding fell short of being proper chemical bonds.

This is a very mechanical model of the covalent bond, whereas the scientific model presents bonding as more of a process than a material mechanical link. However teaching models often present bonding this way, and sometimes molecules are modelled in terms of jigsaws with atoms or radicals as pieces to be slotted together. Although such models are only meant to provide a simple analogy for the bonding they may act as learning impediments if learners take them too 'literally' as realistic representations and transfer inappropriate associations from the model to their understanding of the system being modelled.

Mohammed also uses similar language when asked about salt dissolving in water, as the charge of the water forces the sodium and chlorine ions to slot into certain places within the water molecules *.

Salt is like two atoms joined together

Keith S. Taber

Some learners have been found to see the electron transfer process described by Mohammed (which is purely a way of conceptualising ion formation, and has little connection with what actually happens when ionic substances form) as being the bond, and sufficient to hold species together. However, Mohammed did recognise the role of electrical forces in holding the species together:

And did you say that if you take a sodium atom and a chlorine atom, you get salt?
Yeah… Sodium chloride. And the way they bond together, is because now one, the sodium has lost an electron. And they start off neutral because the protons and electrons balance each other out, because the same number of them, but when you lose one you get plus one in the sodium, and like when you have a chlorine, you add an electron so you get minus one. In the end the whole compound is neutral, but because erm, like they, they're differently charged they attract together, and they bond together. I think.
So if I could imagine a sodium atom and chlorine atom, and then they form salt, what would it look like afterwards? How could I imagine it afterwards.
Oh it's like two atoms joined together.

So here Mohammed is clear (if somewhat tentative) that a bond has been formed. Yet his focus is on the iteration of two atoms, forming ions, whereas ionic bonding needs to be understood as the various interactions at work in a lattice. The process of ion formation described by Mohammed:

would not actually be energetically viable for two atoms (as the electron affinity of chlorine is 364 kJ mol^-1, whereas the first ionisation energy of sodium is 494 kJ mol^-1, so the electron capture of a chlorine atom would not release enough energy to remove the electron from the sodium atom);
neither sodium nor chlorine atoms are stable under normal chemical conditions: neither sodium nor chlorine used in a binary synthesis would be in the form of discrete atoms; and sodium chloride is more likely to be formed by neutralisation using substances where the sodium and chloride ions are already present, e.g. sodium hydroxide and hydrochloric acid.)

Mohammed's explanation conflates two levels – the macroscopic level of bench phenomena (such as the substance sodium chloride – common salt) and the level of models at the submicroscopic scale of molecules, ions and atoms. Even if one atom of sodium could interact ('react' is better kept as a term for what occurs at the level of substances) with one atom of chlorine in the manner Mohammed envisages, to give the "two atoms joined together", that entity could not meaningfully be identified as salt as many of the properties of salts emerge from the ionic lattice of myriad ions.

[If sodium-chloride ion pairs could be formed then we might consider these as the component quanticles of a form of sodium chloride, but this would need to be considered a different allotrope to table salt, just as ozone molecules are not the basis of the oxygen in air that supports respiration.]

In a sponge, the particles are spread out…

In a sponge, the particles are spread out more, so it can absorb more water

Keith S. Taber

Morag was a participant in the Understanding Science Project. In her first term of secondary school, she told me that he had learnt about particles. Morag had explained, and simulated through role play for me, the arrangements of particles in the different states of matter (See: So if someone was stood here, we'd be a solid.) She had also emphasised just how tiny the particles were, "little, little-little-little things", and so how many there were in a small object: "millions and millions and millions". This suggested she had accepted and understood the gist of the scientific model of submicroscopic particles.

Yet as the conversation proceeded, Morag suggested the macroscopic behaviour of sponge in absorbing water could be explained by the arrangement of particles leaving space for the water. This is perhaps a reasonably, indeed quite imaginative, suggestion at one level, except that the material of a sponge is basically solid (where, as Morag recognised, that the particles would be very close together). A sponge as whole is more like a foam, with a great volume of space between the solid structure (where air can be displaced by liquid) and an extensive surface area.

Do you think it is important to know that everything is made of particles?
No.
It's not important?
Well it could be important, but it's not that important. Well, you see, like that [indicating the voice recorder used to record the interview] has got like lots and lots of particles pushed together this [Morag gestures]…But a sponge, the particles are like, the particles are more kind of like, they're still the same, but it's just spread out more, so it can absorb more water.
Oh I see, so are you saying that the same particles are in my little recorder, as in the sponge.
Yeah, they're the same, but there's just more of them in one than there would be in the other.

The failure here is perhaps less Morag's inappropriate explanation, than the tendency to teach about the ideals of solids, liquids and gases, which strictly apply only to single substances, where most real materials students come across in everyday life are actually mixtures or composites where the labels 'solid', liquid' and 'gas' are – at best – approximations.

Teaching has to simplify complex scientific ideas to make them accessible to students of different ages, so often teaching models are used. But sometimes simplifications can cause misunderstandings, and so the development of alternative conceptions. If 'everything is a solid, liquid or gas' is used as a kind of teaching model, or even presented as a slogan or motto for students to echo back to the teacher, when lots of things students come across in everyday life (e.g., butter, clouds, the pet cat – a bathroom sponge) do not easily fit these categories, and this is likely to lead to students overgeneralising.

Although it is often not possible to assign a single simple cause to a student's flawed thinking, this could be considered likely to be an example of a pedagogic learning impediment (a type of grounded learning impediment) in chemistry: a case where an approach to teaching can lead students' thinking in unhelpful directions.

Carbon electrons will be bigger than chlorine electrons

Carbon electrons will have more mass and charge than chlorine electrons

Keith S. Taber

Annie was a participant in the Understanding Chemical Bonding project. She was interviewed near the start of her college 'A level' course (equivalent to Y12). She was shown a representation of a tetrachlomethane molecule.

Understanding Chemical Bonding project – Focal figure 3

When Annie was asked about the diagram, she was not sure if the differently represented electrons would actually be different from each other, She suggested that perhaps electrons from different atoms would actually contain some of the particular element. Annie seemed unsure where one could tell the difference between electrons from different atoms, but her intuition seemed to tell her they should be different,

Under further questioning, Annie was able to suggests ways in which carbon electrons would be different from chlorine electrons. Most science teachers may expect it would be quite obvious that one electron is much like another one in terms of essential properties (e.g., charge, rest mass). We probably assume students will readily appreciate this, and perhaps that it is not a point that needs to be emphasised. We might expect a student would immediately reject any suggestion that electrons from different atoms should be fundamentally different.

Do you think they would be the same size, electrons from carbon and electrons from chlorine?
No.
Which ones will be bigger, do you think?
The carbon ones.
Do you think they're the same charge? The same electrical charge?
No.
(pause, c.5)
No, which one do you think will have a bigger charge?
(pause, c.2s)
The carbon.
…
Yeah, what about colour. What colour do you think they will be?
Colours. What of the actual electrons?
Mm.
Mm, (pause, c.5s) I don't think they'd really have a colour, but I think if they had to have a colour, then they'd pick out the colour from the element.

A teacher is likely to expect an A level student to appreciate that all electrons are intrinsically the same. Annie seemed to think that the electrons of different atoms were different, somehow reflecting the particular element, and open to the idea they may differ in mass and charge, and possibly even colour.

Whilst Annie's comments are at odds with canonical science, they reflect thinking that is quite common among learners who often fail to appreciate the core principle of sub-microscopic models of matter, i.e., that the emergent properties of matter at macroscopic scale are explained in terms of the different properties of the tiny particles (i.e., quanticles) from which matter is conjectured to be constituted at a much finer scale. She was not keeping clearly distinguished macroscopic properties (such as colour) and properties that sub-atomic particles could have.

Electrons would contain some of the element

Electrons from different elements would be different – perhaps because they would actually contain some of the element in the electron?

Keith S. Taber

When Annie was asked about the diagram, she noted that (following a representational convention) the electrons were represented differently. Using different symbols like this is quite common, but is little more that a bookmaking tool – to help keep count of the number of electrons in the molecule in relation to those that would be present in discrete atoms.

…are there any bonds [shown] in that diagram do you think?
Yes.
How many?
Four.
Four bonds, so we've got four bonds there. Erm, are the bonds actually shown?
Yeah.
So how are they represented on the diagram?
By the circles that overlap, and they're showing it by the electrons, the outer-shell electrons in the chlorine have got black dots and the ones from carbon have got just circles.
Okay. So the carbon electrons and the chlorine electrons are signified in a different way
Yeah.

I followed up this point to check Annie understood that the convention did not imply that there was any inherent difference between the electrons.

So what would be the difference between a carbon electron and a chlorine electron?
(pause, c.5s)

The expected answer here was 'no difference', but the pause suggested Annie was not clear about this. So I set up an imaginary scenario, a kind of thought experiment:

If I gave you a bottle of electrons – which I can't do – how would you be able to tell chlorine electrons from carbon electrons – in what ways would they be different?
They would be different because, erm, I don't know if they would actually contain some of the element in the electron.
Do you think they might have little labels on some with "C"s and some with "Cl"s or
Yeah, I don't know if you got an electron, and you could sort of if you took one single one you could say, right that's chlorine and that one's carbon.
You are not sure, you are not sure if you could, or not?
No.

The idea that an electron might contain some of the element seems to miss the key idea that macroscopic phenomena (samples of element) are considerer to energy from extensive ensembles of submicroscopic particles ('quanticles').

Annie did not seem too sure here – perhaps her intuition was that a carbon electron would be different to a chlorine electron, but she could not suggest how. Electrons have no memories, and there is no way of knowing whether an electron has previously been part of a particular atom (or ion or molecule). A free electron is not meaningfully a chlorine electron or a carbon electron. However, students do not always appreciate this, and may consider that free electrons in some sense belong to an atoms they they derived form, and even that this may later have consequences (as with the 'history' conjecture in thinking about ionic bonding).

Annie went on to suggest that carbon electrons would be bigger than chlorine electrons.

An element needs a certain number of electrons

An element needs a certain amount of electrons in the outer shell

Keith S. Taber

Bert was a participant in the Understanding Science project. In Y10 Bert was talking about how he had been studying electrolysis in class. Bill had described electrolysis as "where different elements are, are taken out from a compound", but it transpired that Bert thought that "a compound is just a lot of different elements put together"*. He seemed to have a tentative understanding that electrolysis could only be used to separate elements in some compounds.

if they're positive and negative then they would be able to be separated into different ones.
So some things are, some things aren't?
Yeah, it matters how many electrons that they have.
Ah. [pause, c.3s] So have you got any examples of things that you know would definitely be positive and negative?
Well I could tell you what happens.
Yeah, go on then.
Well erm, well if a, if an element gives away, electrons, then it becomes positive. But if it gains, then it becomes negative. Because the electrons are negative, so if they gain more, they just go a bit negative.
Yeah. So why would an element give away or gain some electrons? Why would it do that?
Because erm, it needs a certain amount of electrons in the outer shell. It matters on what part of the periodic table they are.
Okay, let me be really awkward. Why does it need a certain number of electrons in the outer shell?
[Pause, c.2 s]
Erm, well, I don't know. It just –

So Bert thought that an element "needs a certain amount of electrons in the outer shell" depending upon it's position in the periodic table, but he did not seem to recall having been given any reason why this was. The use of the term 'needs' is an example of anthropomorphism, which is commonly used by students talking about atoms and molecules. Often this derives from language used by teachers to help humanise the science, and provide a way for students to make sense of the abstract ideas. If Bert comes to feel this is a sufficient explanation, then talk of what an element needs can come to stand in place of learning a more scientifically acceptable explanation, and so can act as a grounded learning impediment.

References to atoms needing a certain number of electrons is often used as an explanatory principle (the full shells explanatory principle) considered to explain why bonding occurs, why reactions occur and so forth.

Bert's final comment in the short extract above seems to reflect a sense of 'well that's just the way the world is'. It is inevitable that if we keep asking someone a sequence of 'well, why is that' question when they tell us about their understanding of the world, they eventually reach the limits of their understanding. (This tendency has been labelled 'the explanatory gestalt of essence'.) Ultimately, even science has to accept the possibility that eventually we reach answers and can not longer explain further – that's just the way the world is. Research suggests that some students seem to reach the 'it's just natural' or 'well that's just the way it is' point when teachers might hope they would be looking for further levels of explanation. This may link to when phenomena fit well with the learner's intuitive understanding of the world, or tacit knowledge.

Bert's reference to an element needing a certain amount of electrons in the outer shell also seems to confuse description at two different levels: he explicitly refer to substance (element), when he seems to mean a quanticle (atom). Element refers to the substance, at the macroscopic level of materials that can be handled in the laboratory, whilst an atom of the element (which might better be considered to gain or lose electrons) is part of the theoretical model of matter at a submicroscopic level, used by chemists as a basis for explaining much macroscopic, observed behaviour of samples of substances.