Group size affects racial makeup of friend groups

Being able to choose friends from larger populations discourages friendships with people from other races, finds a study examining the mathematical underpinnings of self-seeking behavior and group size. The results suggest that activities that give people from different backgrounds the opportunity to work together in the classroom can promote multicultural friendships among students.

People often do self-segregate, says Stanford’s Matthew Jackson, an expert in social economics and networks who was not involved with the new work. That sorting can occur thanks to external factors, such as people of the same socioeconomic class going to the same school in their poor or rich community. Such segregation has consequences — such as influencing whether a student applies to college — and the new study does a good job at getting at how group size plays a role in that segregation, Jackson says.

“As you build larger schools, the way people bump into each other is affected,” he says.

The new study describes mathematically how the size of a group influences who hangs out with whom. Sociologist Yu Xie and his University of Michigan colleague Siwei Cheng created a computer simulation in which a certain number of agents (representing students) made friendships with each other. The simulated population was 80 percent one race and 20 percent another, and the researchers assumed that members would prefer friends belonging to the same race as themselves.

As the researchers ran the simulation, they varied the size of the populations from 50 to 1,000 people. As group size grew, the number of interracial friendships decreased, the researchers report April 15 in the Proceedings of the National Academy of Sciences.

That finding was mirrored in data on high school friendships from the National Longitudinal Study of Adolescent Health, the researchers report. In a large school, for example, an Asian student was much less likely to have a non-Asian friend than in a smaller school.

The study’s assumptions do oversimplify things — what people look for in a friend is likely to be different at a small rural school than at a bigger urban school, for example, says John Yun, director of the University of California Educational Evaluation Center in Santa Barbara who was not involved in the study. But the primary finding — that interracial friendships are more likely in smaller groups — highlights the importance of promoting interracial friendships in the small setting of a classroom using teaching or curricular strategies.

When people are exposed to many perspectives and backgrounds, everyone’s better off, Yun says. Research suggests that in schools that are racially integrated, for example, students think more critically, are more likely to pursue higher education and are more likely to participate in civic activities, such as voting.

Two hallmarks of the modern age — the Internet and increased urbanization — make it easier than ever today for people to find and stick with people that are much like themselves, says study coauthor Xie. The study results emphasize the need for continued vigilance in promoting integration, he says.