When the association between appearance and outcome contaminates social judgment: a bidirectional model linking group homogeneity and collective treatment.

Group formation is an inevitable consequence of social life, and the tendency to perceive people as a collective unit persists once they have been categorized as a group. Drawing on the concept of homogeneity, the authors propose a model suggesting that groups may endure in part because people who are perceived as homogeneous attract collective treatment (e.g., monetary rewards and punishment), and such treatment further reinforces the perception that the group's members are homogeneous. In support of this model, more homogeneous groups attracted collective treatment and collectively treated groups seemed to be more homogeneous thereafter. The authors suggest that these effects arise in part because people intuitively believe that group homogeneity is associated with collective treatment, and they present evidence suggesting that this applies to at least one policy-relevant real-world setting.