LAUSR

Abstract Homophily—social grouping on the basis of similar traits—is a well-established intergroup dynamic. However, some evidence suggests that homophily emerges as a byproduct of people's inferences about desirable qualities (e.g. trustworthiness, openness to experience) in others. We apply this social inference approach to studying how people form groups on the basis of their attachment styles. In a behavioral tracking study involving large samples of strangers interacting in a sports stadium, we found that people affiliate with others who share their degree of attachment avoidance, but who do not share their degree of attachment anxiety. These findings are consistent with evidence that avoidantly attached individuals—but not anxiously attached individuals—display qualities they find desirable in others. It also suggests that accounts of intergroup behavior and social identity that treat similarity as an interpersonal goal might not capture the psychological processes behind group formation, and that a more nuanced social inference approach is needed to explain large-scale patterns of social grouping.