In daily life, people regularly encounter unknown others, and they tend to categorize them in terms of their social category memberships, such as sex (i.e., male, female), race (e.g. , Black, White, Asian, etc. ), and emotion (e.g., happy, angry). These perceptions occur rapidly from merely a glimpse of a face or body and often produce judgments that are more evaluative in nature. Prior research examining how observers perceive others focused largely on understanding the perception of individuals. In daily life, however, we often encounter others in groups rather than in isolation. Little is known about how people quickly and accurately form impressions of groups. The proposed research builds on recent theoretical advances to test how individuals perceive groups of people. This research will provide important insights about how observers form meaningful impressions that impact their judgments, decisions, and behaviors about others. This research has important implications for social perception, stereotyping, and vision perception research. <br/><br/>The research tests hypotheses about the mechanisms that underlie the social perception of groups. One set of experiments tests the means by which observers accurately perceive a group’s composition (e.g., the ratio of men to women) by examining how variations in group composition, the physical appearance of group members, and the visual behavior of observers impact the accuracy of group percepts. Another set of experiments tests how members of a group are perceived as sub-groups and individually (i.e. visual assimilation or contrast). Other experiments explore the consequences of these patterns by seeking to understand how groups are evaluated by observers, leading to inferences that a group might be either hostile or hospitable to the perceiver. A final set of experiments seeks to test the mechanisms of group perception for groups that occur naturally in society (e.g., members of corporate boards, faculty rosters from university departments, and panelists at scientific conferences). This research will contribute to our understanding of the social perception of groups. The research illuminates how groups and contexts can contribute to or explain group stereotypes.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.