The sibling rivalry that divided a town - Jay Van Bavel and Dominic Packer

In the years before World War Two, a pair of brothers worked together as shoemakers in the German town of Herzogenaurach. But during the war, the siblings had a terrible argument— a fight so explosive it split the family business in two. At first, the feud only infected their newly competing personnel. But over the coming years, this disagreement divided all of Herzogenaurach. Residents became fiercely loyal to one brand of shoe. Local businesses chose sides and marriage across lines was discouraged.

Herzogenaurach eventually became known as “the town of bent necks” because its residents looked down to ensure they were interacting with members of their group. But could such a serious divide really be about shoes? Doesn’t it take more significant cultural differences to produce this degree of conflict? To answer this question, we can turn to social psychologist Henri Tajfel and his collaborators at the University of Bristol.

This team developed the minimal group paradigm, a methodology designed to investigate the minimal conditions required to turn people against each other. Their plan was to gather participants without the usual factors that lead to hostility, such as religious, ethnic, gender, or other cultural differences. Then, they would split into groups, and run them through scenarios that added one variable at a time to see what stirred up conflict.

But first, they needed a control condition— a pair of groups without any group bias. The researchers told participants they were being grouped based on their ability to estimate things correctly or incorrectly; but in reality, the groups were totally random. Since the researchers ensured none of the participants interacted, no one could form any judgments or personal bonds. Then everyone was given resources to distribute.

Each participant was free to give resources to members of either group, and importantly, everything was anonymous. So whatever a participant decided, it had no impact on how many resources they personally would receive. With all the ingredients for discrimination removed and no reason for competition over resources, the scientists assumed this would make a conflict-free baseline for further research.

But even in these groups, where membership was only defined by a perceived similarity in possessing an arbitrary skill, individuals still showed in-group bias. They consistently gave more to members of their own group than the out-group. Later, research went even further, informing participants that the only thing determining their group membership was a coin flip. But group bias still occurred.

The minimal groups of “us” and “them” were enough. So, in the absence of stereotypes, resource conflicts, and status differences, what was left? What could possibly account for people showing clear preferences for the most temporary and meaningless of groups? The answer that came to Tajfel and his colleagues was social identity. People regularly use group membership to help determine their sense of identity.

And these minimal group experiments suggested that simply being categorized as part of a group is enough to link that group to a person’s sense of self. Then, in an effort to create a meaningful identity, participants allocated more resources to their in-group than the out-group— pursuing their group's interests despite no clear benefit to themselves as individuals.

Variants of these experiments have been conducted around the globe, examining how a shared sense of “us” can affect our attention, perception, memory, and emotions. The mental processes behind minimal group distinctions appear to be the same as many of those that underlie real group identities. So it is possible that these seemingly insignificant differences can harden into much more serious divides.

That said, minimal groups don't always drive people apart. Bringing individuals together in a new group can temporarily help people overcome entrenched biases. However, these positive effects are easily negated by external factors that reinforce existing group identities. Ultimately, the psychology of groups is part of the human condition, and our tendency towards in-group bias is an undeniable part of that.

So it's up to all of us to make our groups and ourselves as inclusive of others as possible.