Reading: Categorization and Representation Physics Problems by Experts and Novices



This article definitely goes on the “top 10” list of physics education research. It is an early article in the field (1981), but been cited an immense 3600 times, meaning it really has stood the test of time.

The authors investigate the difference in experts and novices at solving physics problems. The novices being students who have finished a first year uni course, and the experts being wither PhD students or professors.

The first task required test subjects to group a bunch of problems together in sets that had similarities. Experts group problems based on the major physics principle (conservation of energy, Newton’s Laws) needed to solve them. Novices on the other grouped problems based on their surface features. These included objects such as springs, ramps etc, and key words such as force or velocity.

Later tasks delved deeper to further investigate the thinking process in experts and novices. Novices used the surface features of a problem to search for an equation. Once with an equation, they hoped it would lead them to a solution, or an intermediate solution where they could use another equation to further advance them.

Experts were sometimes able to guess the major physics principle involved after reading  only 20% of the problem. They further confirmed, or readjusted their view as they read on, and had planned an overall “attack” on the problem, knowing how to get to solution without mentioning or reciting a single equation. After the plan was clear, they could then start looking for initial values and choosing appropriate equations.

One piece of research I would love to do is to replicate this in NZ. Do our best and brightest (scholarship winners) think like this? Can we train students to think like this? Does a modeling approach seek to improve students thinking to this level?

Certainly a great piece of research, and I’m sure I will come back to it a number of times.


Reading: Misconceptions or P-Prims: How May Alternative Perspectives of Cognitive Structure Influence Instructional Perceptions and Intentions?

David Hammer


Alot of Physics Education Research discusses the “misconceptions”, or “preconceptions” that students bring into the classroom. Hammer discusses the theory of DiSessa that this might not actually be the case. Instead students might be calling on underlying phenomenological primitives, or p-prims.

The difference in the two is that “misconceptions” are fully formed structures or models in the brain.

“For example, in one popular demonstration of misconceptions, students were asked to explain why it is hotter in the summer than in the winter (Sadler, Schneps, & Woll, 1989). Many responded that this is because the earth is closer to the sun. T  see this response as a misconception is to understand it as part of the students’ knowledge system: The question accessed that stored (and faulty) element of knowledge about why it is hotter in the summer. Another interpretation would be that the students constructed that idea at the moment. This construction would be based on other knowledge, such as the (appropriate) knowledge that moving closer to the sun would make the earth hotter, but it is not necessary to assume that the idea itself existed in some form in the students’ minds prior to the question.

DiSessa (1988, 1993) developed an alternative account of students’ intuitive physics knowledge, positing the existence of more fundamental, more abstract cognitive structures he called phenomenological primitives or p-prims. By this view, how students respond to a question depends on which p-prims are activated.

For example, the question of why it is hotter in the summer may activate for them a p-prim connecting proximity and intensity: Closer means stronger. This p-prim is an abstraction by which one may understand a range of phenomena: Candles are hotter and brighter the closer you get to them; music is louder the closer you are to the speaker; the smell of garlic is more intense the closer you bring it to your nose. It may be through the activation of closer means stronger that students generate the idea that the earth is closer to the sun in the summer. That most people would have this primitive in their knowledge system, and that it has a high probability of being cued in the seasons question, is an alternative explanation for why many students give such a response.”

There are a number of other p-prims apart from “closer is stronger”, and these include ” actuating agency, dying away, resistance, interference, and Ohm’s p-prim”.

The author then gives a transcript of a discussion of motion with his high school class, and explains it in terms of misconceptions and p-prims. He doesn’t give us his opinion on the more relevant theory, but lets the reader see how the different frameworks might lead to different actions by a teacher.

Reading: An introduction to Physics Education Research

Robert Beichner


The article is a summary of the history of physics education research in the US. From beginnings with Karplus and Arons, to McDermott, and towards the big names of Hake, Hestenes, Beichner, Zollman and Fuller.

Its a good read, and hard to summarise (it is a summary itself). But it has helped to clarify how some of the ideas, and people fit together in this field. Its definitely a good read at this point in my journey through physics education research. Not sure how it would go as an actual introduction.

It also gives me lots of directions to go in terms of my readings. “4. Research Trends”, “4.1 Conceptual Understanding”, “4.2 Epistemology”, “4.3 Problem Solving”, and “4.4 Attitudes” all have a number of references I would to pursue.

Reading: Investigation of student understanding of the concept of velocity in one dimension

David E. Trowbridge and Lillian C. McDermott

Article (accessed through sci-hub)

This is one of the earliest articles (1980) into physics education research, and is written by Lillian McDermott, a professor at the University of Washington. Here she interviews a number of undergraduate students to check their understanding of the concept of velocity. She uses interviews students and shows them a demonstration of two balls on tracks. One rolls at a constant speed (A), and one slows down on a ramp (B). The due to the inital speed of ball B, the balls pass each other twice (see below)

mcdermott vel 1

Their results show a surprising number of students (who are in university physics courses) confused a number of elements of the question

  1. They often confused velocity and position. That is, students thought when the balls were passing, they had the same velocity
  2. Acceleration was also confused with, as often the ball B, when behind ball A (but with a higher velocity, and about to pass ball A) was said to be “speeding up”, although it was constantly decelerating (up the ramp)
  3. Some students disagreed with the concept of instantaneous velocity, that is when probed to think about the velocity of ball at “an instant”, they assumed that this concept doesn’t exist (“objects cannot really have a speed for an instant; for speed to be calculated, there must be an interval of time. For an instant the objects have no speed, just a location.”)

Further interviews involved a ball slowing down (ball B) and one speeding up, but they never pass each other. And there are a number of other conceptual question that were added to exams including:

Tell whether the following statements are ALWAYS TRUE:

  1. On the freeway, if two cars reach the same speed, then they MUST be side by side
  2. If two objects both reach the same position at the same clock reading, then they must have the same speed at that one instant. 

This article is followed by one on students understanding of the concept of acceleration.

Forces – why are they so hard to teach?

I was thinking the other day about why we bother teaching Hooke’s Law. It just seems foreign from kids experience to ask them to calculate a spring constant. Why?

Bare with me as I try and answer that question.

Forces don’t exist. Well, to our eyes they dont. You can not actually see any force arrows in our day to day lives. Forces are a model that humans have developed to describe interactions. 

If I ask a novice physicist to look at an inanimate object, a book, they would say there are no forces on it. I sympathize with them. There are a range of other misconceptions that students must get through on the road to understanding the scientific model of forces.

Forces is a hard, abstract concept to learn. But in my own experience, when we try and teach it, we give them a set of hodge-podge rules. What do I mean by this? It seems every teacher teaches the conventions slightly different. Some arent woried about how the arrows are drawn, The labels will be different to different teachers. Some only acknowledge a very few number of general forces, others are happy with dozens of different types. Sometimes the labels are single letters, others have object/agent notation. But each teacher has a slightly different mental model for forces, so thats why they teach it differently.

In the FCI, nearly every high school student will get the truck/car (newton 3rd) question wrong. This is because you can see accelerations, and not forces, and so kids think accelerations are forces. But you cant see forces. They are an interaction. You see their effects.

We go on about how much of a genius Newton was, but then I see teachers spending 1 lesson developing the force concept with their kids. If he was so smart, then surely we can appreciate that the force model is hard to teach/learn?

This brings to why I think we have historically taught Hooke’s Law.  The experiment is the first to reliably and consistently measure forces. So calculating the force constant is not the point of a Hooke’s law lesson. The point is that the extension is proportional to spring length. Because now we have a force ruler. And now we have a way for kids to start to see forces.

2>4 ?

A quick talk, which I found on Dan Meyer’s blog. He argues that we should be “listening to (2) students, not for (4) an answer”. It think this for me sums up how I feel about whiteboard meetings. Sure, there are some places I want the conversation to go, but its more important for me to listen to the kids reasoning skills and thinking patterns, than to tick off a list of facts the kids need to cover.

Reading: Film: “Dont tell me, I’ll find out”

Robert Karplus


This film was made as Karplus and his team were developing and rolling out the K-6 science program in California called SCIS (Science Curriculum Improvement Study).

I nearly jumped out of my seat with joy at 4:20 when a little girl devised an experiment to find out if the “poo” in their aquarium was coming from the fish or the snails.

A huge smile came to my face as a little boy figured out that the fruit flies life was cyclical at 11:00.

These kids and their teachers are exploring aquariums, seeds and germinating, hatching fruit flies, counting  beans (life cycle of plants), crickets (the insect) and chameleon, the go on field trips (to a field!, and a creek)

Also the teachers are superb at asking questions using the Socratic method. Well, I’m not even sure its that, they are posing good questions, and then letting the kids answers dictate where the conversation goes. Maybe it is Socratic questioning.

I really enjoyed this – I will certainly have to follow up and find more readings on SCIS.