People form in-groups from even trivial, arbitrary distinguishing features

Evidence

A critical question to be addressed in any consideration of intergroup relations is, “How do in-groups and, by extension, out-groups, come about?” Tajfel (1970, 1978, 1981) provided one answer to this question— an admittedly incomplete one—when he discovered that people often display a propensity to group themselves and those around them into meaningful social categories on the basis of even trivial features, and to use these groupings in evaluating others who are, or are not, included in the grouping. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1375

Categorization

• XREF: Connects to the minimal group paradigm research stream in social psychology.
• SEED: The finding that trivial features seed meaningful group identification is a springboard for an essay on how arbitrary, tiny distinctions become entrenched social divisions.