Cognitive dissonance is an uncomfortable feeling caused by holding two contradictory ideas simultaneously. The theory of cognitive dissonance proposes that people have a motivational drive to reduce dissonance by changing their attitudes, beliefs, and behaviors, or by justifying or rationalizing them. It is one of the most influential and extensively studied theories in social psychology.
Dissonance occurs when a person perceives a logical inconsistency in their beliefs, when one idea implies the opposite of another. The dissonance might be experienced as guilt, anger, frustration, or even embarrassment. The idea of “sour grapes” comes from the fable The Fox and the Grapes by Aesop. The fox is unable to reach the grapes, and, experiencing cognitive dissonance, reduces that dissonance by believing the grapes are sour. This example follows a pattern: one desires something, finds it unattainable, and reduces one’s dissonance by criticizing it.
A powerful cause of dissonance is an idea in conflict with a fundamental element of the self-concept, such as “I am a good person” or “I made the right decision.” The anxiety that comes with the possibility of having made a bad decision can lead to rationalization, the tendency to create additional reasons or justifications to support one’s choices. A person who just spent too much money on a new car might decide that the new vehicle is much less likely to break down than his or her old car. This belief may or may not be true, but it would reduce dissonance and make the person feel better. Dissonance can also lead to confirmation bias, the denial of disconfirming evidence, and other ego defense mechanisms.