In-Group Bias has deep evolutionary roots. Ancient humans used these biases to promote group cohesion and survival. It’s likely that humans evolved these tribal instincts long ago to keep their own group safe from competing groups and tribes.

The formal study began with Social Identity Theory, developed by Henri Tajfel and John Turner in the 1970s, which explored how individuals derive positive self-worth from the groups they belong to.

They conducted experiments that showed how individuals categorize themselves into groups and favor those in their own group, even when the group distinctions are completely arbitrary or trivial.

These experiments showed how easy it was for humans to form into groups and to discriminate against those they considered completely outside of their group.

Racism might be the first thing we think of when we think of in-group bias, but it’s worth noting that humans can very easily form into their own groups and treat those they don’t consider as part of their group with disdain.

This bias can foster strong bonds and collaboration among team members. But it can also lead to conflicts with other teams, impacting cross-functional collaboration. Think about how often designers butt heads with product managers or engineers. Or how often product teams in larger orgs refuse to share learnings or work with each other.