Juries sometimes render verdicts that run counter to the evidence presented. Community groups take radical stances on issues before thinking through all the ramifications. Groups can stumble, but groups that make disastrous decisions require special explanation. Groupthink, which was coined by Irving Janis in his classic book Victims of Groupthink, is considered a disease that infects healthy groups, rendering them inefficient, unproductive, and irrational. Janis has identified a number of causes of groupthink, and many were likely operating in the Heaven's Gate group.
Groupthink only occurs in cohesive groups.
Such groups have many advantages over groups that lack unity. People enjoy their membership much more in cohesive groups, they less likely to abandon the group, and they work harder in pursuit of the group's goals. But extreme cohesiveness can be dangerous. When cohesiveness intensifies, members become more likely to accept the goals, decisions, and norms of the group without reservation. Groupthink groups work in secret.