Shared identity alone, not kinship or history, triggers exclusion

Evidence

The laboratory experiments with the minimal intergroup situation demonstrated that ethnocentric loyalty and bias clearly do not depend on kinship or an extensive history of interpersonal relationships among group members, but can apparently be engaged readily by symbolic manipulations that imply shared identity and a clear distinction of who is “us” and who is “them”—a rule of exclusion as well as inclusion. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 2482

Categorization

• QUESTION: What symbolic manipulations most reliably engage ‘us-them’ distinctions in large-scale modern societies — and does this bear on nationalism and polarization debates?