In-Group Bias

In-group bias is the tendency to favor members of one's own group over members of an out-group in evaluations, resource allocation and behavior, even when the groups are formed on a trivial or arbitrary basis. The effect has been demonstrated experimentally using minimal groups created by essentially meaningless distinctions, showing that mere categorization into groups, without any history of conflict or competition, is sufficient to produce favoritism toward one's own group. Social identity theory explains the bias as arising from people's tendency to derive part of their self-esteem from the standing of the groups they belong to.