What Groups Do to Us
Put people into a group and their thinking and effort shift in predictable ways.
Group polarization is the tendency for group discussion to strengthen the members' initial leanings rather than moderate them. A group of mildly cautious people, after discussing, becomes more cautious; a group of mildly risk-tolerant people becomes more daring. Discussion does not average opinions toward the middle — it pushes them toward the extreme the group already favored.
Groupthink, named by Irving Janis, is a deeper failure mode: in a highly cohesive group under pressure to agree, the drive for harmony overrides realistic appraisal of alternatives. Dissent is suppressed, doubts are self-censored, and the group develops an illusion of unanimity and invulnerability — producing disastrous decisions that no individual member would have made alone. Its remedies include encouraging dissent, appointing a "devil's advocate," and seeking outside views.
Group presence also changes effort. Social facilitation is the finding that the presence of others improves performance on simple or well-practiced tasks (but worsens it on difficult, novel ones). Social loafing, by contrast, is the tendency to exert less effort when working in a group where individual contributions are pooled and cannot be identified — each person eases off, assuming others will carry the load.
Common pitfall: confusing social facilitation with social loafing. Facilitation concerns performance when others merely watch you (an audience), and it typically boosts simple tasks. Loafing concerns effort when you work within a group on a pooled task, and it reduces each person's effort. Watched vs. pooled — opposite effects.