How a Stanford professor liberates large lectures

In a Nov. 29 talk, Timothy Bresnahan, the Landau Professor in Technology and the Economy, described his approach to teaching students in large lecture classes: know them, challenge them, liberate them.

L.A. Cicero Economics Professor Timothy Bresnahan

Economics Professor Timothy Bresnahan gave his first teaching tip at the start of his talk, "Large Classes: Keeping the Energy in 220 Relationships at Once," by saying he would be sitting down during his presentation.

"This is my first trick for you," he told a noontime audience assembled around a conference table in the Mitchell Earth Sciences Building. "You want your students to be active; you've got to be a little passive."

Speaking last week at a session of the brown bag lunch series Award-Winning Teachers on Teaching, Bresnahan said one way he practices passivity in his statistics class is to simply "shut up" after giving students a fun problem – such as testing the theory that storks bring babies, using data about the number of human births and the number of stork nests in English towns.

After discussing the data, which suggested that storks bring babies, Bresnahan said he stops talking, a technique he called "the most important tool of wiliness."

"After three minutes, I'll say, the reason I got this job is I'm paid by the hour, I'm perfectly happy to sit here until somebody has something intelligent to say," he said.

"At minute six, I'll say, you guys do know the correct theory, right? We deliberately picked an incorrect theory. At eight minutes, I'll say, OK, maybe there are some people that don't know the true theory here. You engineering students, you can ask after class and I'll tell you the true theory. And eventually, even among 21st-century students, somebody will say, could it be that this is a correlation that's not causal?"

Bresnahan said he doesn't let them stop talking until they arrive at an explanation.

"It's easy to say this statistical model is false," he said. "It must be correlation, not causation, when you know the right answer. But in a live example, you don't know the right answer. So I will push the students, once they start talking, to tell me why this one came out that way. I'll ask them, 'Why do we get this correlation?' And eventually someone really, really smart will say there are probably more storks and moms in the bigger towns and that's why you get this correlation. Which is a very, very good answer for a sophomore."

Know them. Challenge them. Liberate them.

Bresnahan said large lecture classes present three challenges: keeping students energized; drawing them into the intellectual community associated with their majors and into the Stanford intellectual community; and teaching them the tools they will use in advanced economics classes.

He presented a three-part strategy: Know them. Challenge them. Liberate them.

Bresnahan said he memorizes the names of all 220 students enrolled in his large lecture classes, after reviewing photographs – taken by teaching assistants – of each student holding a sheet of paper with his or her name written in large letters.

"This is me being an overachiever," he said of his memorization routine. "I don’t think I'm a particularly charismatic lecturer; I don't think I can carry the room. I do think that I can reach out to people and induce them to think by calling their name."

At a minimum, he said, learn the names of 15 to 20 students by taking them to lunch.

"This is a terrific investment," Bresnahan said. "First off, you'll know if what you're doing is playing. And second, you'll have people to call on when you want somebody to say something other than you, which is really, really important."

Bresnahan said he tries to create "challenges to active thinking everywhere," such as posing an interesting question about a problem students have just solved.

After a class of sophomores had solved a problem set about two groups of people and wages, testing the difference between two means, he asked: Which group do you think came from East Palo Alto and which group came from Atherton?

"This is a significantly easier question than all the technical stuff they've just done, but a very substantial fraction of Stanford sophomores, almost all men, will say, 'Wait a minute, you didn't teach us that,'" he said.

Asking questions about material not covered is a "really good trick, very reliable," Bresnahan said.

"Someone will pop up in class during question time and say, 'How are we supposed to know that?'" he said. "You say, 'You're supposed to be a capable, working person.'"

Bresnahan suggested picking advanced undergraduates as teaching assistants – students who took the course last year and had a lot of fun – as a way to reduce the "social distance" between the people who teach and the people who learn.

"To go back to my original theme, it's easy to get a large body of knowledge – or tools – across to these highly motivated, hard-working students," he said. "To get them to feel you really want them to take up these tools and use them, you've got to go a little out of the box."

As for liberating students, Bresnahan said it's important to "turn them loose" to make discoveries on their own. "I let them show off," he said.

Bresnahan said he gives students the chance to shine with a weekly "submit-a-slide contest," in which a student gets seven minutes to present a slide illustrating the best or worst statistical analysis found in that week's Wall Street Journal or San Francisco Chronicle. He said the exercise is "incredibly empowering" for students, and since it's not counted toward their grades, it's not threatening.

The prize for winning Bresnahan's "build-a-data-set contest," which requires students to form teams of at least three people, is permission to be a day late on the following week's data set.

"I want to give them a toolkit and encourage them to put it to use on stuff they think is exciting and where they think they have knowledge, because that's a really, really difficult problem for beginning students, to have enough knowledge on top of all your tools to do a serious empirical study," he said. "It's just amazing what they do."

Stanford's Center for Teaching and Learning sponsors the Award-Winning Teachers on Teaching series. A video of Bresnahan's 45-minute presentation, and the question-and-answer session that followed, will be available in January on the center's website.