In an age where public discourse seems more polarized and extreme than ever, finding common ground is key. Easier said than done, however. A new study comes to show that our desire to fit into and belong to certain groups could lie at the root of this issue.

The study found that people who identify themselves as belonging to a particular political group are more likely to be biased against people outside of the group. People identifying either as Democrats or Republicans showed this inclination in equal measure, so it’s not where our affiliation lies that matters — only that we desire to be part of the group. Whether or not it’s political in nature isn’t really important.

Alternatively, if you’re reluctant to identify yourself as part of a group, you’re less likely to be biased in general.

Mine with mine, you with yours

“It’s not the political group that matters, it’s whether an individual just generally seems to like being in a group,” said Rachel Kranton, an economist at Duke University’s Trinity College of Arts & Sciences and lead author of the paper.

“Some people are ‘groupy’ — they join a political party, for example. And if you put those people in any arbitrary setting, they’ll act in a more biased way than somebody who has the same political opinions, but doesn’t join a political party.”

The team began by testing the ‘groupiness’ of 141 participants by asking them to allocate money to themselves and someone else in their group or outside of it in different contexts. For one of the tests, participants were divided into groups based on their (self-declared) political affinity. In the second setting, they were organized into groups based on what paintings or poems they enjoyed, and in the third one the groups were random.

They expected people to discriminate against other groups based on how strongly they believed in the opinions of their group; in this sense, the first scenario should have been the most divisive, as people tend to care about politics more than art preferences.

What the team found, however, was that simply being attached to a group made ‘groupy’ people more biased against outsiders (as compared to people with the same political leanings but who didn’t identify as being a Democrat or Republican). This effect persisted in all contexts.

“There is this very specific distinction between the self-declared partisans and politically similar independents,” says co-author Scott Huettel, a psychologist and neuroscientist at Duke. “They don’t differ in their political positions, but they do behave differently toward people who are outside their groups.”

“We can’t show you that all group-minded identities behave this way,” says Huettel. “But this is a compelling first step.”

Around a third of the participants didn’t show a bias when allocating money regardless of context. They were more likely to consider themselves politically independent, the authors note, and also made the decision on how to allocate money faster on average than their peers.

“We don’t know if non-groupy people are faster generally,” Kranton said. “It could be they’re making decisions faster because they’re not paying attention to whether somebody is in their group or not each time they have to make a decision.”

As to exactly what makes someone ‘groupy’, the team can’t say right now. From their data, however, they can tell it’s neither gender nor ethnicity. There’s just “some feature of a person” that makes them put more value on group divisions, the authors argue. Other research will need to uncover what this feature is, and how it arises.

The paper “Deconstructing bias in social preferences reveals groupy and not-groupy behavior,” has been published in the journal PNAS.