Keith S. Taber
Tim was a participant in the Understanding Science Project. When Tim was interviewed in the first term of his 'A level' (college level) physics course he had been studying the topic of materials with one of his teachers, and "at the moment we're doing about why some materials are brittle, and some aren't, and about the molecules". When Tim was asked about the molecules, he compared molecules to the pieces in a jigsaw:
Interviewer: So what's a molecule?
Tim: Erm it's like a bit of a particle, so, something that makes up something.
I: Have you got any examples?
T: Of a molecule?
I: Yeah, something that makes up something.
T: Erm, like the wood in the table is made out of wood molecules.
I: I see. So, that's one type of molecule, is it, a wood molecule? And there are other types of molecule?
T: Yes it's a bit like a jigsaw, like when you put all the, like you need to put the…, you put them all together to make – something.
I: I see, yeah. So, if I wanted to be really awkward, in what way is it like a jigsaw?
T: Erm, well they sort of fit together, like in a jigsaw some bits are sort of straight and have nice parallel, a nice parallel microstructure, and some, some jigsaws have funny bits that don't fit together quite as nicely.
I: I see. So are there some ways it's not like a jigsaw?
T: Yeah. (Tim laughs.) Well, erm, I dunno, it's like a jigsaw in the way that the bits fit together to make something, to make something, but then again, I dunno.
I: I mean, I quite like this idea of it being like a jigsaw – I was wondering whether, whether you had got that from somewhere, or that's just something you'd come up with?
T: No I just thought about it, just then.
I: Oh that's really creative.
T: It's quite random actually. (laughs)
Tim's comments about a molecules being a bit of a particle was followed up later in the interview, and it transpired he was not sure if a molecule is a bit of a particle – or vice versa.*
So when asked to explain about molecules in materials, Tim used an apparently spontaneous analogy of this being like a jigsaw, with different types of pieces that fitted together. Moreover, he also seemed to recognise that different materials had molecules that fitted together more or less readily, and materials could also be considered to have similar diversity. Tim described this as being 'random', which seems unfair as the analogy clearly has merit, but presumably saw it this way as the comparison had apparently appeared in his consciousness unexpectedly (i.e., the thought had 'popped into his mind', as a kind of insight.)
Tim seemed a little phased by being asked to explain the negative features of the analogy – and this may reflect the tendency to focus on the positive aspects of an analogy, rather than its limitations. Analogy has the potential to channel student thinking in inappropriate directions (e.g., as associative learning impediments) when not considered critically. However, analogies also have potential to help 'make the unfamiliar familiar' and so can be a powerful learning tool.
