Perceivers form strong inferences of disposition from others' facial appearance, and these inferences guide a wide variety of important behaviors. The current research examines the possibility that similar-looking individuals are more likely to form groups with one another. We do so by testing a necessary downstream consequence of this process, examining whether the faces of individuals within groups more physically resemble one another than those in other groups. Across six studies, we demonstrate that individuals' group membership can be accurately classified both from ratings of members' faces, and from direct measurement of members' faces. Results provide insight into how affiliative groups initially form and maintain membership over time, as well as the perception of homogeneity of groups.
Keywords: face perception; group formation; impression formation; intragroup dynamics; person perception.