Group membership is chosen to balance simultaneous needs for inclusion and distinctiveness.

Evidence

According to ODT (Brewer, 1991), social identity is conceptualized as deriving from a “fundamental tension between human needs for validation and similarity to others (on the one hand) and a countervailing need for uniqueness and individuation (on the other)” (p. 477). Membership in moderately sized groups is considered to be optimal because there is a sufficient number of other individuals in the group, which allows for a sense of inclusion and belonging with other group members. At the same time, however, the group can be used as the basis for distinguishing the individual from nongroup members, thereby satisfying the need for distinctiveness. For example, a person may choose to join a group of sailing enthusiasts because doing so provides a sense of belonging with fellow sailors, while simultaneously allowing the individual to be distinguished from others (e.g., runners). — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 830

Categorization

• XREF: Provides mechanism-level frame (inclusion/distinctiveness tradeoff in ingroup formation) that could complicate or sharpen the Islamophobia/antisemitism claims in the prior Allport reassessment thread.
• corroborated: 2 independent passages support this claim — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 830