Cognitive dissonance – a state characterized by a clash in the mind of the individual contradictory knowledge, beliefs, behaviors with respect to some object or phenomenon. The theory of cognitive dissonance – one of the "theories of compliance, based on assigning individual commitment to a connected and orderly perception of their relationship to the world. The concept of "cognitive dissonance" was first introduced by a student of Kurt Levin, Leon Festinger in 1956 to explain the changes, opinion as a way to resolve semantic conflicts. In the theory of cognitive dissonance is logically contradictory knowledge about the same subject ascribed status of motivation designed to ensure correct issues when confronted with contradictions discomfort due to changes in existing knowledge or attitudes. It is believed that there is a body of knowledge about objects and people, called the cognitive system, which may be varying degrees of complexity, consistency and coherence. The complexity of the cognitive system depends on the number and diversity included in her knowledge.

According to the classical definition of L. Festinger, cognitive dissonance – the discrepancy between the two cognitive elements (cognition) – thoughts, experiences, information, etc. – In which denial of one element follows from the existence of another, and the associated mismatch discomfort, in other words, a feeling of discomfort arises in a collision in the minds of logically contradictory knowledge one and the same phenomenon, event, object. The theory of cognitive dissonance describes how to resolve these contradictions, or smoothing, and describes how it makes people in typical cases.