He (Janis) lists some of the symptoms of groupthink in his study of high-level governmental decision makers. Prime among these is the sharing of an illusion of invulnerability which leads to over optimism and causes planners to fail to respond to clear warnings of danger and be willing to take extraordinary risks.
Second, the participants in groupthink ignore warnings and construct rationalizations in order to discount them.
Third, victims of groupthink have an unquestioned belief in the inherent morality of their ingroup actions, inclining the members to ignore the ethical or moral consequences of their decisions.
Fourth, victims of groupthink hold stereotyped views of the leaders of enemy groups. They are seen as so evil that there is no warrant for arbitration or negotiation or as too weak or too stupid to put up an effective defense.
Fifth, victims of groupthink, says Janis, apply direct pressure on any individual who momentarily expresses doubts about any of the groups shared illusions, or questions the validity of the arguments.
Sixth, unanimity becomes an idol. Victims of groupthink avoid deviating from what appears to be the group consensus; they keep silent about their misgivings and even minimize to themselves the importance of their doubts. Victims of groupthink sometimes appoint themselves as “mindguards” to protect the leader and fellow members from adverse information.
Janis quotes Robert Kennedy as having taken one of the members of the group aside and told him, “You may be right or you may be wrong, but the President has made his mind up. Dont push it any further. Now is the time for everyone to help him all they can.” Janis also lists some of the symptoms of the resulting inadequacy of problem-solving. Among these are the limitation of discussion to only a few alternative courses of action, the failure to reexamine some of the initially preferred and now discarded courses of action, and the failure to seek information from experts within the same organization who could supply more precise estimates of possible losses and gains from alternate courses of action.