What are group dynamics?

Groupthink is a pattern of flawed decision-making that occurs in cohesive, insulated groups that prioritise harmony and consensus over critical evaluation. The group develops an illusion of invulnerability, suppresses dissenting views, and fails to properly examine alternatives. Janis documented groupthink in case studies of US foreign policy disasters — including the Bay of Pigs invasion — and identified remedies such as appointing a devil's advocate, inviting external criticism, and encouraging independent sub-group analysis.

Social loafing is the tendency to put in less effort when working as part of a group than when working alone. It happens for two main reasons: first, individual contributions are less identifiable in group work, reducing accountability; second, responsibility for the outcome is shared, so each individual feels less personally responsible for success or failure. Social loafing is reduced when individual contributions can be monitored, when the task is personally meaningful, when group members know each other well, or when group norms explicitly value high effort.

Deindividuation is a psychological state in which individuals in a group lose their sense of personal identity and individual responsibility — becoming more susceptible to group norms and impulses, and less governed by personal values and self-regulation. It is promoted by conditions such as anonymity (wearing uniforms or masks), high arousal (crowds, noise, darkness), and diffuse attention. Deindividuation has been used to explain crowd violence, online disinhibition and aggression, and the behaviour of soldiers in war.

The bystander effect is the finding that people are less likely to offer help in an emergency when other bystanders are present. Latané and Darley found two key mechanisms: pluralistic ignorance (each bystander looks to others for cues; seeing no one reacting, they assume there is no emergency) and diffusion of responsibility (each person assumes someone else will help). The effect is strongest in large groups of strangers. Research shows that the bystander effect can be overcome by making explicit requests for help from a specific individual, or by providing bystanders with knowledge of the effect itself.

Group polarisation is the tendency for group discussion to push members toward more extreme versions of their initial positions. If the group initially leans toward a risky choice, discussion makes them riskier; if they lean conservative, discussion makes them more so. Two mechanisms drive this: persuasive arguments (discussion surfaces more arguments favouring the dominant view) and social comparison (members want to appear at least as extreme as, or more extreme than, the group average). Group polarisation can escalate conflict, reinforce prejudice, and drive extremism.