Psychology professor Daniel T. Gilbert and economics professor N. Gregory Mankiw asked the audience, “What is your N?” in a conversation about psychology, economics, and happiness on Monday. The talk aimed to engage students in a cross-disciplinary debate about why people make the choices that they do.

“I actually thought about this question last night, because it was date night in the Mankiw household,” Mankiw said.

Organized and moderated by professors Nicholas A. Christakis and David I. Laibson ’88, the event was sponsored by the Harvard University Initiative on the Foundations of Human Behavior.

“Both Nicholas and I are big believers that making social science more interdisciplinary is going to be fruitful,” Laibson said. “We believe that the different social scientists should come out of their silos from time to time and talk to one another across the standard disciplinary boundaries.”

The speakers proposed a hypothetical situation to the audience. A person had to choose between different types of alcohol to maximize happiness. The moderators asked the audience to vote on a value of N from one to 100, with N representing the number of types of alcohol that they could choose between. The audience could have a maximum of 100 options or could limit their choices by picking a lower value of N. Both Mankiw and Gilbert predicted that students would choose values for N between 70 and 90.

“I think that an economist has to choose larger Ns,” said Mankiw. “I’d be inclined towards a larger N, and I’d want someone to give me a larger N if they were choosing for me.”

Gilbert said that he estimated in this range because he guessed that Americans “don’t want Big Brother in there choosing for [them].”

The results from online voting, in which 220 students participated before and during the program, were streamed in real time during the event. Participants were asked to submit their responses for two hypothetical scenarios: one in which they were choosing a value for a participant who knew that originally there were 100 choices and another in which the participant was unaware of the number of options that they had.

Student results were lower than Gilbert and Mankiw had predicted for both scenarios.

The low N values that students voted for surprised some students as well as the speakers and moderators.

“I wasn’t surprised by my position and I wasn’t surprised by Professor Mankiw’s position, but I was very surprised by the data they collected. I thought most people would expect maximal choice to be best,” Gilbert said.

However, some students said that their views were in line with other students and that Mankiw’s and Gilbert’s opinions were unexpected.

“I was surprised that both Mankiw and Gilbert thought that the numbers would be so high. My own choices were much lower, and I expected that other people would select lower numbers too,” Rachel E. Zax ’12 said.

Laibson and Christakis hope that this event will be the first of many events in a series of social science talks.

“It was a great event, and I think probably the first of many that Professor Christakis and Laibson will organize as they attempt to put the bio-social sciences on the map,” Gilbert said.

—Staff writer Megan B. Prasad can be reached at mprasad@college.harvard.edu.