contagion theory

psychology

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June 24, 2026

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Contagion theory, in the context of psychology and collective behavior, suggests that moods, emotions, and behaviors can spread rapidly through a group, similar to how a sickness spreads. Early theories, like those of Gustave Le Bon and Sigmund Freud, viewed collective behavior as a regression to a more primitive state, where individuals in a crowd lose their sense of self and become highly suggestible, slavishly identifying with a leader.123

More recent interaction theories, such as contagion and convergence theories, propose that collective behavior arises from intensified social interaction. Contagion theory emphasizes the rapid spread of moods and behaviors, while convergence theory highlights how individuals with similar predispositions come together. These theories aim to explain why groups act unanimously and intensely, sometimes in ways that differ from their usual behavior.1

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deindividuation
Origins of deindividuation theory
…loss of control leads to contagion, in which a lack of responsibility spreads throughout the crowd and everyone begins to think and act in the same manner. Finally, people in crowds become more suggestible.
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…loss of control leads to contagion, in which a lack of responsibility spreads throughout the crowd and everyone begins to think and act in the same manner. Finally, people in crowds become more suggestible.
Read More

collective behavior
Interaction theories
…interaction theories have been labeled contagion and convergence theories, respectively—the former stressing the contagious spread of mood and behavior; the latter stressing the convergence of a large number of people with similar predispositions. Both have sought to explain why a group of people feel and act (1) unanimously, (2) intensely,…
Read More
…interaction theories have been labeled contagion and convergence theories, respectively—the former stressing the contagious spread of mood and behavior; the latter stressing the convergence of a large number of people with similar predispositions. Both have sought to explain why a group of people feel and act (1) unanimously, (2) intensely,…
Read More