Sociologist Irving Janis used this term to refer to the collective tunnel vision that group members sometimes develop. As they begin to think alike, they become convinced that there is only one "right" viewpoint and a single course of action to follow. They take any suggestion of alternatives as a sign of disloyalty. With their perspective narrowed and fully convinced that they are right, they may even put aside moral judgments and disregard risk.
Groupthink can bring serious consequences. For example in 1941, President Franklin D. Roosevelt and his chiefs of staff had evidence that the Japanese were preparing to attack Pearl Harbor. They simply refused to believe it and decided to continue naval operations as usual. The destruction of the U.S. naval fleet ushered the United States into World War II.
Groupthink is a danger for government leaders, who tend to surround themselves with an inner circle that closely reflects their own views. In "briefings," written summaries, and "talking points," this inner circle spoon-feeds the leaders the information it has selected.
The result is that top leaders, such as the president, become largely cut off from information that does not support their own opinions. Perhaps the key to preventing the mental captivity and intellectual paralysis known as groupthink is the widest possible circulation.