Leon Festinger's work on cognitive dissonance is one of the landmark achievements in American psychology. First developed in A Theory of Cognitive Dissonance (1957), the theory explained how people were capable of believing one thing despite evidence to the contrary. Festinger argued that, above all else, people sought to maintain consistency in their worldview, their ideology, their belief systems, and their attitudes. When facts or evidence come along that disturb that consistent worldview, a state of cognitive dissonance sets in. Cognitive dissonance, Festinger wrote, is a motivational state which contains within it a set of mechanisms--or triggers--that bring consistency back to a person's thinking, even if it means distorting or ignoring facts and reality.

Writing in the ideological rigid Cold War climate of the 1950s, at a time when the pressure for social conformity was an increasingly recognized problem in American life, Festinger tried to explain how people tried...