Groupthink is a phenomenon which occurs in groups, where the overwhelming influence of others decision in a group changes the decisions of others in a group. This often leads to groups agreeing on something unanimously, though individuals in the group may have different opinions. Because of the social influence a group can have upon an individual, their beliefs are often set aside and replaced with those beliefs which are valued by the group.
In the movie/play 12 Angry Men, 12 men must decide on the fate of a boy who has been accused of murder. At the first vote, many of the men vote guilty, and when the others in the group see that the majority are voting guilty, they also join, as they are susceptible to groupthink. The vote is almost unanimous, and only one man votes innocent.
Throughout the movie, this one man must try to reverse the group think by using many of the solutions proposed in the book. They call for many revotes, he plays the devils advocate and proposes counter arguments, and many varying opinions are considered. Though it is very difficult to reverse the ‘groupthink’ decision, he is eventually successful.