In 1990, Eric Mazur, a physics professor at Harvard University, came across some data that showed college students didn’t improve their scores on a conceptual test of Newtonian mechanics after taking introductory physics. Mazur wondered if that would be the case for Harvard students, so he gave the students in his intro physics class the test.
“I was dragged out of my ivory tower,” Mazur said. “The gain [after taking the intro class] was abysmal. It was clear I was not doing a good job teaching physics.” Mazur realized that the students had become quite adept at solving problems by rote, but not at applying concepts. So the next time he taught the course, he took some class time to explain some of the misconceptions exposed by the test.
“I turned and looked at them, 80 students or so, and they looked totally confused,” he said, “as if my explanation had made them more confused. They were silent, so confused they couldn’t even formulate a question.” From the test results, Mazur knew that about half of the students understood the concept he was trying to explain. “On a whim, I said ‘why don’t you turn to your neighbor and convince them of your answer,’ ” he said. “The whole room burst into chaos.”
The students were suddenly so eager to talk physics that Mazur said he figured, “I have to formalize this.” Such was the birth of “ peer instruction ,” a method of teaching that now has thousands of science faculty members bagging the traditional back-to-the-class lecture.
Conversation is generally regarded as a staple of humanities courses, but standard lectures still dominate the science classroom. “It’s 2,000 years after Socrates,” Mazur said, “and we’re still doing this. If I’m a humanities teacher, I wouldn’t just read Midsummer Night's Dream to the students. In the sciences, we’re reading much less interesting authors than Shakespeare.” So Mazur developed a classroom approach that allows the students to teach each other constantly as he asks questions. In just two years, the gains over the class indicated by the conceptual test doubled. Mazur spread the word, and now the spread of technology has added a new piece to peer instruction at many institutions.
When students show up for an intro biology class with Michael Klymkowsky, a University of Colorado at Boulder biology professor who uses peer instruction, they have to have their “clickers.” Now and then, Klymkowsky will break from lecture and pose a conceptual question. Like eager game show contestants, the students buzz in their answers, and only the professor can see the distribution of answers. If too many students are wrong, Klymkowsky will have students try to convince one another of an answer, and then pose the question again and re-evaluate the distribution.
“They telegraph back to the instructor the ideas that are not understood. The standard lecture never reveals to the student or the lecturer what the misconceptions are, so they’ll never go away,” Klymkowsky said. Several faculty members at Colorado, where peer instruction is widespread, guessed that perhaps 10,000 students have clickers. In the past, physics has often been the testing ground for peer instruction, but it has gone beyond the physics department. Klymkowsky is part of a group using a National Science Foundation grant to develop a conceptual biology test  that can be used to assess gains using peer instruction in biology. That test is expected to be ready next academic year.
At Colorado, peer instruction is already being used in astronomy, math, biology and physics classes, with geosciences and physiology to come. But even at institutions where peer instruction has proliferated, many professors are skeptical. Andrew Staehelin, a Colorado biology professor, has seen a lot of novel techniques in his 40 years of teaching, and doesn’t think that peer instruction fits some courses. Staehelin teaches intro to cellular and molecular biology, a 400-student class, and he said that “80 percent of the curriculum is learning vocabulary, and what these different components do.” Staehelin added that the laws of physics that are taught in intro courses have not changed in 50 years, while in biology “the material has evolved further. I’m constantly presenting things not even in textbooks,” he said, which could be a problem in a peer instruction classroom where professors often refer students to the textbook for some of the more rote learning.
In some cases, students haven’t exactly cuddled up to peer instruction either. In 2001, thanks to a peer instruction push by John Belcher, a physics professor, the Massachusetts Institute of Technology built the “Technology Enabled Active Learning,” or TEAL classroom, in the place of an old physics library. The TEAL classroom, rather than having chairs facing a blackboard, has 13 circular tables to facilitate peer instruction for groups of nine students. The students not only discuss questions at their tables, but collaborate on experiments and exercises. At MIT, all students have to take introductory physics. The failure rate, normally 10-15 percent, was cut in half after the TEAL center was built, and students showed increased gains on concept tests. Belcher said that peer instruction also helps the students learn how to “formulate ideas verbally.”
Though students are flocking to the TEAL center, they aren’t wild about it. When the students respond to in-class questions via clickers, they are not scored for a correct answer, but they do earn participation points, so they have to come to class. “It’s a tradition at MIT, not going to these large classes,” Belcher said. He added that some of the students complain that being forced to attend is “treating them like high school students.”
In the spring of 2003, student evaluations of introductory physics had about a full point drop, on a seven-point scale, in the “satisfaction” category. Things have gotten somewhat better, Belcher said, and he added that many more students now fill out the evaluations, so the increased dissatisfaction could be, for example, the result of students who don’t like showing up for class now showing up on evaluation day.
Some instructors simply feel that peer instruction professors have more fun. Judith Herzfeld, a chemistry professor at Brandeis University is the only teacher in her department who uses peer instruction, and she isn’t going back. “It’s actually fun,” she said of her general chemistry class where students hold up colored cards to respond to questions. “I wouldn’t go back to teaching any other way.”
Herzfeld said the structure prepares students for the kind of engaged learning they’ll have to do after college, while giving her feedback that keeps the life-long-learner in her happy. “Many teachers who don’t grade exams get no real time feedback. I get feedback eight times an hour,” said Herzfeld, who added that, without tenure, she would not have taken a risk on peer instruction. Even with the in class response system, though, Herzfeld realized that some students are still self-conscious about answering. “I’m doing eight questions an hour with 100 students, and some thought I would remember everything they got wrong,” she said. Herzfeld used a grant from the Camille and Henry Dreyfus Foundation to develop in class questions, available online , for other general chemistry teachers.
Before Mazur, who has written a book  on peer instruction, started using his technique, his student evaluations would sometimes criticize him for lecturing straight from the notes he distributed. “I never get that remark anymore,” Mazur said. “Now I get, ‘Professor Mazur doesn’t teach anything. We have to learn it all on our own.’”