Predicting that birds of a feather will flock together: Expectations of homophily for others but not the self

Similarity among friends – or other socially connected individuals – is a ubiquitous characteristic of social networks. There are several, often simultaneous, mechanisms (e.g., social influence, shared environments) through which such links between social connection and similarity arise, including homophily, or the tendency for similar people to attract one another. While past research has found that people use similarity heuristics to structure their mental representations of social networks (predicting that friends are likely to be similar to each other), it is unknown if people assume such similarity arises through homophily, specifically. Here, we tested if people assume that homophily will shape their own and others’ future friendships. Participants (total N = 560) learned how (i) trustworthy and (ii) trusting various partners were through repeated trust games. Participants predicted which partners would become friends with one another and which partners they would become friends with themselves if they were to meet in person. Across two studies and both trait measures, we found that participants were significantly more likely to predict that partners who behaved similarly would later become friends compared to those who behaved dissimilarly. Interestingly, we found that participants were significantly more likely to predict that they would become friends with highly trustworthy and highly trusting partners compared to highly untrustworthy or highly untrusting partners, regardless of their own behavioral tendencies or even their own self-perceptions. These findings suggest that people assume homophily for others’ relationships but not their own. Such expectations likely shape how people approach or foster new friendships for themselves and between others.