Collective behavior consists of those forms of social behavior in which the usual conventions cease to guide social action and people collectively transcend, bypass, or subvert established institutional patterns and structures. As the name indicates, the behavior is collective rather than individual. Unlike small group behavior, it is not principally coordinated by each-to-each personal relationships, though such relationships do play an important part. Unlike organizational behavior, it is not coordinated by formally established goals, authority, roles, and membership designations, though emergent leadership and an informal role structure are important components. The best known forms of collective behavior are rumor, spontaneous collective responses to crises such as natural disasters; crowds, collective panics, crazes, fads, fashions, publics (participants in forming public opinion), cults, followings; and reform and revolutionary movements. Social movements are sometimes treated as forms of collective behavior, but are often viewed as a different order of...