causal thinking - Science-Education-Research

Sleep can give us energy

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

Keith S. Taber

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

And earlier in the year, you were doing about dissolving sugar. Do you remember that?
Erm, yeah.
Do you think that's got anything to do with the human body?
Erm, we eat sugar.
Mm. True.
Gives us energy…It powers us.
Ah. And why do we need power do you think?
So we can move.

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

Ah what if you were a lazy person, say you were a very lazy rich person? And you were able to lie in bed all day, watch telly, whatever you like, didn't have to move, didn't have to budge an eyelid, … you're rich, your servants do everything for you? Would you till need energy?
Yes.
Why?
I dunno, 'cause being in bed's tired, tiring.
Is it?
When I'm ill, I stay off for a day, I just feel tired, and like at the end of the day, even more tired than I do when I come to school some times.

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

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

So maybe when you are ill, you should come to school, and then you would feel better?
No.
No, it doesn't work like that?
No.
Okay, so why do you think we get tired, when we are just lying, doing absolutely nothing?
Because, it's using a lot of our energy, doing something.
Hm, so even when we are lying at home ill, not doing anything, somehow we are using energy doing something, are we?
Yes.
What might that be, what might we use energy for?
Thinking.

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

Do you think it uses energy to think?
(Pause, c.3s)
Probably.
Why do you think that?
Well cause, like, when you haven't got any energy, you can't think, like the same as TV, when it hasn't got any energy, it can't work. So it's a bit like our brains, when we have not got enough energy we feel really tired, and we just want to go to sleep, which can give us more energy, a bit like food.

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

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

So sleeping can give us energy?
Yeah.
How does that work?
Er, it's like putting a battery onto charge, probably, you go to sleep, and then you don't have to do anything, for a little while, and you, then you wake up and you feel – less tired.
Okay so, you think you might need energy to think, because if you have not got any energy, you are very tired, you can't think very well, but somehow if you have a sleep, that might somehow bring the energy back?
Yeah.
So where does that energy come from?
(Pause c.2s)
Erm – dunno.

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

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

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

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

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

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

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

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

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

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

Because they're wearing red…

Cause and effect?: People go to different places because of what they are wearing

Keith S. Taber

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

Iron is too heavy to completely evaporate

Some molten iron would evaporate but not all of it, 'cause it's not like water and it's more heavy

Keith S. Taber

Sophia was a participant in the Understanding Science Project. In her first interview near the start of Y7, Sophia told me that she had learnt "about the particles…all the things that make – the actual thing, make them a solid, and make them a gas and make them a liquid" (i.e. the states of matter). All solids had particles, including (as examples) ice and an iron clamp stand. There would be the same particles in the ice as the iron.

"because they are a solid, but they can change , 'cause if erm they melted they would be a liquid so they would have different particles in…Well they are still the same particles but they are just changing the way they act".

Sophia's suggestion that particles in ice and the iron were the same types of particles as both were solid seems to be 'carving nature' at the wrong joints – that is in this model the particles in ice and (solid) iron would be of one type, whilst those of water and liquid iron would be of another type (that is she had an alternative ontology). Sophia quickly corrected this, so it is not clear if this reflected some intuitive idea or was just 'a slip of tongue'.

According to Sophia the ice could be melted "with something that's hot, like a candle" but for the iron "you need more heat, 'cause it's more, it's a lot more stronger…because it's got more particles pushed together".

Sophia's explanation suggested a causal path (right-hand side) quite different from a canonical causal path (left-hand side)

Strictly the difference is more about the strength of the interactions between particles, than how many were pushed together – although strong bonding forces would tend (all other factors being equal) to lead to particles being bound more tightly and being closer. We might argue here that Sophia seemed to confuse cause and effect – that a higher density of particles was an effect of strong bonding, which would also mean more energy was needed to overcome that bonding. (However, we should also be aware that when students use 'because' (which formally implies causality) they sometimes mean little more than 'is associated with'.)

If the water obtained from melting ice was heated more "it will evaporate into the sky". However, if the molten iron was heated Sophia thought that "some of it would evaporate but not all of it, 'cause it's not like water and it's more heavy". She thought only "a little" of the iron would evaporate to give iron vapour:

"No, I think that water all of it goes, but other material, other liquids some of it will go, not all of it". The rest "if it's cold enough, it will go back into a solid, but if not it really just stays as a liquid".

Sophia's idea that no matter how much liquid iron was heated it would not completely evaporate so some would remain liquid, which seemed to be linked in her mind to its density, seems to be evidence of an alternative conception. Students may not expect that something as (apparently) inherently solid as iron could evaporate (everyday experience may act as a grounded learning impediment), and so may not readily accept that the basic model of the states of matter and changes of state (i.e., a heated liquid will evaporate or boil) can apply to something like iron. Sophia seemed to have formed a hybrid conception – applying the taught model, but with a modification reflecting the counter-intuitive notion that iron could become a vapour.

Conceptual change can be a slow progress, although hybrid conceptions may be 'stepping stones' towards more scientific understandings. However, when I spoke to Sophia in Y8 she did not seem to have progressed further. [See 'Liquid iron stays a liquid when heated'.]