Groupthink occurs when the pressures to conform are so great, that independent thinking and action are restricted. The primary symptoms of groupthink include:

• Illusion of invulnerability-- the team believes that it's decision making is beyond question, which creates excessive optimism and encourages extreme risk taking.
• Belief in the inherent morality of the group-- this inclines members to ignore the moral or ethical consequences of their decisions
• Collective rationalization-- these efforts lead to the team discounting warnings that might have otherwise led them to reconsider their assumptions before they recommit to past policy decisions.
• Out-group stereotypes-- others are framed as too evil or stupid to warrant consideration of their strategies or attempts to negotiate with them.
• Self-censorship-- members feel inclined to avoid deviation from concensus, and minimize the significance of their doubts and counterarguments
• Illusion of unanimity-- partly from the silence of self-censorship, members share the belief that they are unanimous in their judgements; silence means concensus.
• Direct pressure on dissenters-- challenges or sanctioning comments are made to those who express strong arguments against the team's stereotypes, illusions, or commitments; loyal members do not bring up questions.
• Self-appointed mindguards-- these members protect the team from adverse information that might threaten the shared illusions regarding the effectiveness or morality of the team's decisions.