"As a result of informational signals and reputational pressures, groups run into four separate though interrelated problems. When they make poor or self-destructive decisions, one or more of these problems are usually to blame:
Groups do not merely fail to correct the errors of their members; they amplify them.
They fall victim to cascade effects, as group members follow the statements and actions of those who spoke or acted first.
They become polarized, taking up positions more extreme than those they held before deliberations.
They focus on what everybody knows already—and thus don’t take into account critical information that only one or a few people have."