Decomposing an interaction: Part 3

Two years ago, I heard Leslie give a fascinating talk at FFPER (2009) about different argumentation styles. My (likely flawed) memory of the talk is that if one person (let’s call them A) thinks that ‘proving something’ means ‘proving everything else wrong,’ and another person (let’s call them B) thinks that ‘proving something’ means ‘coming up with a reasonable (affirmative) explanation,’ these two people are going to have very different ideas about what it means to explain something. A may not accept B’s explanation, and vice versa.

I thought about Leslie’s talk as I was watching the extended interaction with Stamatis and group 1 (see my other thoughts on this interaction here and here). It seems to me that what group 1 accepted as an answer to Stamatis’ questions and what Stamatis considered a ‘sufficient’ answer were two different things entirely.

Throughout the morning, the teachers have been discussing the energy transfers and transformations that happen as a hand pushes a block across a (frictionless) surface. Their task is to answer the question, “Why do these transfers and transformations happen,” or “What is the mechanism by which these transfers and transformations happen?”

In the following episode, Stamatis is (in my view) trying to get the teachers to make explicit their (implicit) explanatory mechanisms. (Earlier, Tim had given him an answer about a friction-ful situation, and Stamatis seemed to feel that Tim was – implicitly – using a mechanism to predict particular transfers and transformations.) In the episode below, when the teachers say that energy is being transferred from the hand to the block, and Stamatis asks, “How is the hand transferring energy?,” the group responds, “By a contact force.” Stamatis then comes up with a situation in which that ‘explanation’ falls apart. Take a look:

My interpretation of this episode is that the teachers were satisfied with their answer – that, to them, a contact force transfers energy was a reasonable (and sufficient) answer to the question. But it wasn’t sufficient for Stamatis – because he could think of an example in which this ‘wouldn’t work.’

The group continues to discuss forces (off and on), and they have added (to their original criterion) that there not only needs to be a force, but an unbalanced force (although Don can think of systems in which there is a transfer of energy but no net force). Stamatis summarizes the group consensus and then says something to the effect of: “Let’s try this unbalanced force criterion out…Let’s think of ten cases where this is happening and let’s try to think about a case where it’s not happening.” (emphasis mine) Watch and see:

It seems to me that Stamatis considers an answer (evidence?) ‘rigorous’ or ‘sufficiently robust’ when one cannot think of a counterexample. The teachers, on the other hand, may not share this ‘argumentation style’ (for lack of a better word). In some cases, I wonder if the teachers interpreted Stamatis’ pushing them to refine their criterion (by examining counterexamples) instead as him saying, “No, that’s not right.” Might this mismatch in ‘argumentation styles’ have been a sticky point in this (extended) interaction?

Parts 4 and 5 tomorrow...