deindividuation

Deindividuation is a psychological state in which individuals experience a reduced sense of personal identity and self-evaluation, often accompanied by a diminished concern for social evaluation. In this state, people are more likely to follow the crowd and act impulsively, sometimes in ways that contradict their usual standards. Deindividuation arises in situations of anonymity, high arousal, large crowds, or shared group identity, and is shaped by diffusion of responsibility and reduced self-awareness.

The concept has roots in crowd psychology. Early ideas attributed crowd behavior to anonymity and contagion, with Le Bon arguing that individuals in crowds suspend their personal constraints. In modern social psychology, deindividuation has been demonstrated in experiments showing that disguises or online anonymity, high arousal contexts, or large numbers can increase willingness to violate norms or engage in disinhibited behavior. The phenomenon is not inherently antisocial; it depends on the norms prevailing in the group. The social identity model of deindividuation effects (SIDE) argues that anonymity heightens reliance on group norms and social identity, rather than suppressing self-awareness, guiding behavior.

Critics caution that deindividuation is not a single mechanism and that context, norms, and individual differences determine outcomes. Some replications fail to find robust effects, and positive or prosocial acts can also emerge under deindividuated conditions. In contemporary settings, cyberdeindividuation describes how online anonymity can lead to flaming or harassment, though it can also align with charitable or cooperative acts when group norms favor such behavior.

See also: crowd psychology, social identity theory, online disinhibition effect.