The term cognitive dissonance refers to the mental tension experienced by an individual who holds contradictory beliefs, ideas, values, or preferences at the same time. A typical example refers to the situation that arises when an individual holds certain beliefs or values but, for whatever the reason, performs an action that contradicts those beliefs or values.

The theory of cognitive dissonance, as proposed by Leon Festinger, postulates that humans strive for internal consistency. Psychological discomfort arises as a consequence of experienced dissonance, and the individual attempts, consciously or unconsciously, to reduce the dissonance. One possible method is to adjust his or her own attitudes or beliefs. This can be illustrated through the fable of the fox and the grapes, attributed to Aesop (ca. 620–564 bce). In ...