Basic recipe for human groups does not require race, politics or religion

(Phys.org) —People do not need race, religion, or politics to divide themselves into groups—all it takes is the presence of two simple and well-established principles of psychology, a team led by researchers at Yale University and the University of North Carolina has shown.

A simple computer model shows that the recipe to create "us versus them" would be familiar to any member of a schoolyard clique. First, people tend to like people who are nice to them. Second, people tend to like friends of their friends—and conversely—dislike enemies of their friends.

Nothing else is required for in-groups and out-groups to form, even within populations that are similar in every other respect, according to the study, to be published in the journal Psychological Science.

"It is hard to tease out root causes of group formation because observable differences such as race or language may arise because people already live in groups," said David Rand, assistant professor of psychology at Yale and co-lead author of the study. "What we show is that you can strip away all those factors, and groups will still emerge."

In fact, humans' propensity to self-segregate can summed up in just 80 lines of computer code. Rand and co-lead author Kurt Gray, together with a team of other scientists, created a computer simulation that assigned numerical values to how much each pair of individuals in a population "liked" each other. Like real people, the virtual people in their simulation were more likely to cooperate with those they liked more and felt more positively towards people who cooperated with them. In this scenario, pairs of friends and enemies would form at random, but not in larger groups. However, groups formed robustly once the simulation incorporated "friends of friends" effects: If you are nice to me, I not only like you more, but also like your friends more (and dislike your enemies).

The researchers created an interactive tool that lets you explore how the structure and composition of groups can change by manipulating the strength of those two factors.

Groups themselves can be complex and sustained by a large number of factors., say the researchers, and more studies are needed to explain multi-group formation and why individuals typically belong to many groups in a variety of social contexts. But entrenched groups can emerge even without the factors such as race or religion, they note.

"We talk about post-racial, post-religious America—the idea that we can put people into a melting pot and dissolve differences to make people a unified people," Gray said. "But the thing is that people get into groups naturally, even if they literally don't see race, or even understand that there is an 'us versus them.'"