When someone tells a lie and feels uncomfortable about it because he fundamentally sees himself as an honest person, he may be experiencing cognitive dissonance. That is, there is mental discord related to a contradiction between one thought (in this case, knowing he did something wrong) and another (thinking that he is honest).

Psychologist Leon Festinger published the book A Theory of Cognitive Dissonance in 1957. Among the examples he used to illustrate the theory were doomsday cult members and their explanations for why the world had not ended as they had anticipated. Many experiments have since been conducted to illustrate cognitive dissonance in more ordinary contexts.

No.

Hypocrisy involves a contradiction between a person’s supposed principles, beliefs, or character and who they really are or how they behave. Cognitive dissonance is the unpleasant mental state that may result if someone really does have certain beliefs but thinks or acts in a way that contradicts them.

It’s not clear.

While cognitive dissonance is often described as something widely and regularly experienced, efforts to capture it in studies don’t always work, so it could be less common than has been assumed. People do not necessarily experience discomfort in response to every apparent contradiction in their thoughts and beliefs.

Cognitive dissonance poses a challenge: How can we resolve the uncomfortable feeling that arises when our own thoughts or actions clash with each other? Some responses may be more constructive than others.

A man who learns that his eating habits raise his risk of illness feels the tension between his preferred behavior and the idea that he could be in danger. He might ease this feeling by telling himself that the health warning is exaggerated or, more productively, by deciding to take action to change his behavior.

If a woman reads that her favorite politician has done something immoral, she could conclude that the charges have been invented by his enemies—or, instead, rethink her support.

There are a variety of ways people are thought to resolve the sense of dissonance when cognitions don’t seem to fit together. These may include denying or compartmentalizing unwelcome thoughts, seeking to explain away a thought that doesn’t comport with others, or changing what one believes or one’s behavior.

Not necessarily.

By bringing attention to the inconsistencies in our minds, cognitive dissonance may present an opportunity for growth. People who feel it could realize, for example, that they need to update their beliefs to reflect the truth, or change their behavior to better match the person they want to be.