This post is part of a series on the Science of Learning Physics
One of my favorite discoveries in my cognitive science journey is the expert vs novice thinker conversation, particularly as it relates to physics. Daniel Willingham discusses this in his book Why Students Don’t Like School, “experts don’t think in terms of surface features, as novices do; they think in terms of functions, or deep structure.” In Dr. Jose Mestre’s book he talks about an experiment where students were asked to sort physics problems. The experiment showed that novice students tend to sort problems by surface features whereas the “experts” sorted the problems by the big idea, specifically the major physics concept used to approach the problem.
Part of what makes physics, as a course, so difficult for all students is the necessity to move towards an expert type of thinking in order to approach problems. It is an experiment I would love to run formally, but in my experience there is a marked difference between the first 2 weeks of physics and week 10. By week 10 it’s like a switch has flipped for all of the students and the impossible is suddenly possible. Of course, there is no magic switch, rather students have begun to adapt more “expert” ways of approaching problems.
A really great example of exposing novice vs expert thinking is card sorts. Brian Frank has created an abundance of these sorts and they are amazing to work with. I particularly like the way Kelly O’Shea runs her kinematics exercise with students. First students are given just the graphs and asked to organize the cards in any meaningful way. Every time I do this assignment students decide to organize the graphs based on their shape OR they put all of the position graphs together, velocity graphs and so on. They make little to no connections between graphs (such as a parabolic position graph goes with a linear velocity graph etc). When students are satisfied the teacher realizes she forgot to pass out some cards” and drops label cards. These cards begin to get students to reorganize the cards in order to make the cross-connections. This also gives students a “second pass” with the material.
Ok, so it’s easy to see students acting like students, but how to we get them to think like physicists?
Strategies for Training Students
I love this puck problem below. The premise is beautifully simple. Same force, one puck has more mass, compare the change in momentum.
The novice student thinking looks like this:
- Change in momentum is mΔv.
- M is bigger on A, so A has the bigger momentum change.
- FULL STOP. OR……
- M is bigger on A and now I need to calculate v (lots of calculations later and fumble around with force).
The expert thinking looks like this:
- Impulse is equal to change in momentum.
- The force on both is the same.
- The mass on A is bigger, so it will take longer to get it to the finish line.
- Therefore Ft for A is bigger, so mΔv must be bigger.
Students are in shock by how simple and elegant the expert solution is. But it really just comes from ONE critical shift, pulling out the big idea rather than pointing to where change in momentum is explicitly stated.
AP provides another sweet opportunity to practice this skill and it is embedded in the paragraph-length response. Too often students see the format and just start to free-write. I discuss with them that they need to draft their response, much like a typical essay, but in a physics-friendly manner. They should (1) determine the big idea (2) set up the problem as if they were to solve it (3) Any step along the way becomes a sentence or bullet point towards the answer.
I work with students directly on this skill during classwork. I have a series of energy problems that I love to do this with. I have them whiteboard answers for speed and accuracy and I provide some very specific directions (1) Write your conservation statement (2) Write your proportionality statement (3) write your answer.
AP Physics 1 Multiple Choice: The Exemplar of Expert Thinking Processes
Every year I have a few AP students who are so close to an A but can’t seem to push over the edge. Additionally, I often have a handful of students who, if you were to talk to them, clearly have a solid grasp of the content but they absolutely tank the AP Physics 1 multiple choice items. The beauty…and poison of AP Physics 1 multiple choice items is their requirement to think like an expert. The questions and responses are immensely loquacious and even though AP provides students with nearly two minutes per item students tend to fall into two traps: first, they are so used to multiple choice being factual items that you either know or don’t know and move and, and second, they try to be so careful that they lose sight of the forest for the trees. After the exam students frequently get mad that the questions were so “easy” or “obvious” “when you explain it” often placing the blame on me for not providing enough worked examples. Instead, we need to shift the narrative and turn the ownership back to the student. We cannot shame them, instead we need to train them on how to better approach any problem, not the 10 on Tuesday’s test.
I have found that having small group conversations with students about this to be highly effective. Willingham further describes in his chapter about novice vs expert thinking that experts have conversations with themselves which allows them to dissect the problem, focus on the important information and test ideas. Novices, on the other hand, rarely do this due to the cognitive load required of them. Having these conversations with my students helps train them in this type of procedure in order to make them more readily do the process on their own.
We go through the multiple choice items together and I ask them a lot of questions. I ask them to identify the big idea, then I probe them to tell me about components of that big idea that relate to the problem. Only then do we begin to look at the answer options. When you probe about the big idea first, several options quickly show themselves as incorrect. A wonderful example are the multiple choice items that you might label “Newton’s third law”. As soon as a student sees the phrasing how does the force of A on B compare to the force of B on A, the rest of the problem should be irrelevant, whether there are numbers, masses and so on. So if I were working this problem with a student I would ask them to identify it as a force problem, then I would ask them what our class definition of forces is (an interaction between objects) and since a force is defined as such, we can cut through the distractors and identify the correct answer.
Another strategy I use in my classes is I will literally hand them the exam a week prior to test day. However, I have made one very important adjustment: I take the question and all of the letter options off. Instead, students are presented with a scenario and they have the freedom to discuss with their peers the possibilities for the exam. I do this as an in-class activity, so students are not leaving the room with exam questions. Some students have reported back that this process makes them more anxious for the exam because they come up with exceedingly challenging possibilities, however in the end what it does is it allows students to perform on assessment day at the level they deserve. What happens here is, once again, students are engaged in conversations. They can transform these conversations into self-talk when they take the test. The idea that they have the actual exam in their hand means they know a 100% is possible if they talk to everyone, so they do not waste time working alone.
My tagline on this blog is “infecting students with passion” I definitely try to infiltrate their brains in several ways, and moving them towards expert thinking is one of them. As I tell them often, it’s my goal to get them to have conversations with me in their head when they sit an take the exam so it can feel as easy as a real-life conversation and they can knock it out of the park.
So tell me…
- What does expert vs novice thinking look like in your classroom?
- How have you tried to model or scaffold expert thinking and practices for your own students?
- What are you ready to commit to doing differently when we return in January?