Outgroup Homogeneity Bias

Outgroup homogeneity bias, also called the out-group homogeneity effect, is the tendency to perceive members of a group one does not belong to as more similar to one another than members of one's own group are, a pattern often summarized as the assumption that outsiders are alike while one's own group is diverse. The psychologists George Quattrone and Edward Jones provided foundational research on the effect in a 1980 study, finding that people consistently overestimate how uniform an out-group's members are, which supports the view that stereotypes about an out-group tend to be overgeneralizations. The effect has been documented across many kinds of groups, including political, racial, age and gender groups, and researchers continue to debate within social psychology whether it should be understood mainly as a cognitive error or as a normal and even adaptive feature of how people process social information, with self-categorization theory and social identity theory offering two different explanations for why it occurs.