Peer Instruction and Computing

Lectures in higher education correspond to that old Churchill chestnut about democracy: they are the worst of all mass teaching methods, except all the others that have been tried. The criticisms are simple: they are too passive, too monotonous, and students don’t gain much from being there. Various solutions have been proposed from closing all the universities and switching to MOOCs (with, erm, online lectures?) to flipping the classroom and more besides. One early flipped-classroom-style proposal (in the 90s) was Peer Instruction, put forward by Eric Mazur, which I will describe in this post.

Peer Instruction

Mazur was teaching Physics at Harvard. He saw research showing that students’ wrong preconceptions about how the physical world works (along the lines of heavier things fall faster) were persisting despite studying high school physics and university physics. The solution was centred around drawing out and challenging the students’ misconceptions. I’ve previously discussed how to do this in online videos, but Mazur came up with changes to the lecture format to enable this to be done effectively in a lecture theatre.

The basics of Peer Instruction are:

  • Set reading before the class
  • Discuss a topic briefly (say, for ten minutes) in the lecture
  • Propose a conceptual question on the topic, with a right answer, and several answers corresponding to common misconceptions
  • Get the students to answer the question by themselves (e.g. with “clicker” devices or equivalent smartphone apps)
  • Get the students to engage in small group discussions with their neighbours about the answer they gave
  • Get the students to answer the question again via their clicker
  • The lecturer then takes questions from the audience, or clears up misconceptions he/she overhead during the small group discussion

There’s presumably various forces at work here. The question followed by discussion helps students realise when they are wrong (the first step in the battle!) and then students can convince each other of the right answer. Mazur makes the point that students can often provide a well-tailored explanation to each other because they share a novice viewpoint, although presumably you also run the danger of the blind leading the blind. Advocates of Peer Instruction are keen to point out that it’s not just about adding clickers to ordinary lectures. It’s not the technology by itself that makes a difference, it’s the whole protocol.

Concept not calculations

One central argument in the Peer Instruction book is about solidifying concepts, not calculations. Mazur shows that conceptual understanding is relatively orthogonal to the ability to calculate the correct answer on standard textbook/exam questions. This chimed a little with me: I recall drawing lots of force diagrams in mechanics (the physics end of maths) involving a normal force. I was never happy with the concept: the idea of the ground exerting an upwards force was baffling to me. Is the ground really pushing upwards? What would happen if you turned gravity off — would everything fly upwards with the power of the normal force? However, these questions never mattered to my progress: I knew how and where to add the force on the diagram such that the forces would balance and I could get the correct answer. I got through the course successfully despite not understanding many of the central concepts, and Mazur suggests that many physics students are the same. Based on the evidence he provides in his book, Mazur’s Peer Instruction seems to greatly increase conceptual understanding.

The question is the questions

One aspect that seems to be key to peer instruction is picking the right questions. Peter Newbury discusses the issue in a post here — broadly, you need a question that illuminates misconceptions and provokes discussion. All of Mazur’s questions are in physics, so to apply peer instruction to computing, someone needs to develop a bank of computing questions. Enter Beth Simon at UC San Diego, who has been applying peer instruction in huge lectures, with sparkling results (see links to papers at the end of the post). You can get access to questions at the research group’s Peer Instruction 4 CS site.

Here’s an example question, about recursion:

Consider the following code.

void recur (int i) {
    if (i == 0) { 
        printf ("%d ", i); 
    for (int j = 0; j < 2; j++) 
        recur (i - 1); 

What is printed by the call recur (1)?
A. 0
B. 0 0
C. 0 0 0 … infinitely
D. 0 1
E. None of the above

The idea is that each answer to the question traps a different misunderstanding of the code (e.g. confusing i and j, not understanding that two recursive calls will occur, or that the recursion will end).

Picking Groups

I recently had the chance to hear Quintin Cutts (who’s been applying these ideas at the University of Glasgow) and Beth Simon talking about the methodology during this year’s ICER conference. One question that came up was the effect of these small groups: computing tends to have a problem with a wide variance in prior knowledge (and a glut of show-off know-it-alls). Simon teaches primarily non-majors, so tends to have a more even distribution of ability; she assigns groups randomly. Cutts has a more traditional computing intake, and said that he deliberately groups people by ability level. If there is a wide disparity, he said, you lose the peer aspect and it just becomes one student forever teaching another. Equalising the ability level allows for better discussions.

Summary and Further Reading

I find Peer Instruction an interesting methodology and the results seem positive. It’s a teaching method that’s intended for university; I haven’t looked to see if there has been work on applying this pre-university in schools, although there have been questions developed for Alice. I am conscious of the stress that the proponents place on following the protocol closely and accurately. I’m reminded of Coe’s talk from ResearchEd at the weekend where he mentioned findings that worked well in research not necessarily transferring into widespread practice. Certainly there seem to have been several educators who took the message “use clickers” from this work, without achieving any of the benefits because they dispensed with the important other aspects of the protocol.

There are many papers about Peer Instruction in computing. Rather than list individual papers, here’s some links to lists of relevant papers (almost all publicly available): one list here, and another list here.

Also, more material from Peter Newbury about using Peer Instruction and designing questions.

Edit: I see that I forgot to mention explicitly that there is a Peer Instruction book written by Mazur. However, it’s only about 40 pages on Peer Instruction in general, and the rest is a vast collection of physics Peer Instruction book. So if you’re interested in Peer Instruction for other subjects, you may find yourself a little disappointed with how slim the book effectively is.


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