Cognitive Dissonance:

In the late 1950s, Leon Festinger proposed the theory of cognitive dissonance, which is the inconsistency that someone might see between two attitudes or among a performance and an attitude. For example, if a person believes that honesty is significant but lies to a boss about time spent on a project, that person is likely to experience dissonance. Festinger proposed that people would search out a state in which there is the lowest possible dissonance. To achieve this person can do one of four things: He can change his behavior to match his attitudes(Stop lying), he can decrease the importance of the behavior, he can change his attitude (honesty is overrated), or he can seek offsetting fundamentals (I worked last weekend, so exaggerating my hours isn't that bad). If a person is rewarded for dissonant performance (lying while believing honesty is important), the dissonant performance will be attributed to the reward (a higher paycheck) rather than to any interior process.