Humans positively regard the groups to which they belong (i.e., ingroups) and enact favorable beliefs, attitudes, and behaviors toward their groups. Such positive ingroup regard is ubiquitous in the sense that it is evidenced in multiple cultures, arises in response to both momentarily-formed groups and enduring groups, and activates quickly under the most minimal of conditions. By integrating the social psychological literature on groups, multi-level models of human evolution, and a neuroscience literature that details the affiliative effects of the mammalian hormone oxytocin, the proposed research develops and tests a bio-social model of positive ingroup regard. The model suggests that an activated sense of group membership (i.e., "we are a group") triggers the release of oxytocin which in turn promotes a favorable orientation toward the group and its members (i.e., positive ingroup regard). According to the model, positive ingroup regard functions as part of an evolved intragroup social-regulation process that promotes the stability of the group and an individual's membership therein. Three proposed experiments test the bio-social model. Experiment 1 tests whether a sense of ingroupness triggers oxytocin release and whether oxytocin serves as a hormonal mediator of positive ingroup attitudes and behaviors. Experiment 2 examines whether oxytocin is released differentially or differentially affects behavior in an intragroup context that lacks a rival outgroup versus an intergroup context in which a rival outgroup is present. Experiment 3 examines the more nuanced issue of whether oxytocin is triggered in response to ingroup members, the abstract concept of the ingroup, or both individual members and the ingroup construct. By integrating traditional social psychology, evolutionary theory, and the neuroscience literature on oxytocin the proposed research advances the extant conceptual and empirical understanding of why humans positively regard the groups to which they belong.
