Students often come into our class ready to be filled with knowledge about science. They see the knowledge as “out there,” that the teachers are there to give us the truth about the world. But, at least one perspective is that the only thing that is “out there” are the things that we see – the phenomena, the experience. The “explanations” for those things are in our heads. We can never know if we’ve come up with all the possible explanations for, say, the color we see when we look up at the sky. And we can never know if the explanation we’ve come up with could stand every possible test that we could put it to, there might be one more experiment that would change our model.
In other words, scientific concepts are “free creations of the human mind and are not, however it may seem, uniquely determined by the external world (Einstein and Infeld, 1938). In a way, we’re scheme-making creatures, we’re really good at looking for patterns and trends, most likely because this has been really adaptive for our species.
(To give you an idea of the horrid nature of ed-speak, this is how Jammer originally put it: “When science attempts to construct a logically consistent system of thought corresponding to the chaotic diversity of sense experience, the selection of concepts as fundamental is not unambiguously determined by their suitability to form a basis for the derivation of observable facts.” Puh-leeze.)
Anyway. That means that the “folk theory of physics teaching,” that “Physics teaching is the presentation of the established canon of physics by approved methods for the benefit of the deserving” is invalid because we can’t teach physics as a “photographic picture and true image of reality. Instead, the goal of teaching is to engage students in the process of constructing new understanding.
So, we •make up• our explanations for things. But, students don’t come into class as blank slates. They’ve got prior experiences and have explanations for things already, even if they’re not aware of it. So one role of teachers is to help students become aware of their current explanations. We can do that through the old game of asking them to predict what they think will happen, and then discuss their reasons for their predictions. (Dykstra suggests having them first write down what they think, individually, and then discuss amongst their group to determine what the group thinks). We can also do it by showing them something that doesn’t fit their prediction, that is surprising. If students see something that doesn’t fit their explanation they can either say,
– That didn’t happen (ie., question the data)
– Hey, did that really happen? What’s going on here?
If we don’t discount what we saw, then we should change our explanation for what’s going on. That’s the only thing we can change (we can’t change the data, though sometimes we can argue against it). The cycle we can bring our students through in termf of bringing out their prior conceptions and resolving discrepancies is called Elicit – Compare (or Confont) – Resolve – Apply.
Note to teachers – in order to follow the elicit – compare – resolve – apply — you want to pick phenomena that will unequivocally surprise them, not something pretty subtle that they may or may not see what it is that you expect them to. Also, you can get a comprehensive list of student conceptions (with 7700 entries) from the website linked here.
In other words, we want to train our students to be good scientists, to use evidence to test explicit models. It’s not that we want to teach them the “canon of physics,” the set of immutable facts handed down through generations. This scientific tendency and skill has been squashed out of kids throughout their schooling: Leon Lederman says that 5-year kids are great scientists. They ask all the right questions, before we train that out of them.
This, of course, means that our tests must change. We must test students abilities to apply their new models in some new context, not ask them to regurgitate what we already gave them. Otherwise, we’re not testing them on the things that we’re teaching in the class.