A fairly straightforward concept that explains a lot about human behavior:
From Psychology (Schacter, Gilbert, Wegner):
« Leon Festinger called cognitive dissonance "an unpleasant state that arises when a person recognizes the inconsistency of his or her actions, attitudes, or beliefs." Festinger made many major contributions to the field of social psychology, one of which started with this simple observation: When people experience the unplesasant state of cognitive dissonance, they naturally try to alleviate it, and one way to alleviate cognitive dissonance is to change one's actions, attitudes, or beliefs in order to restore consistency among them.
The fact that we often alleviate cognitive dissonance by changing our actions, attitudes, or beliefs can leave us vulnerable to other people's efforts to change them for us. In one study, female college students applied to join a weekly discussion on "the psychology of sex." Women in the control group were allowed to join the discussion, but women in the experimental group were allowed to join the discussion only after first passing an embarrassing test that involved reading pornographic fiction to a strange man. Although the carefully staged discussion was as dull as possible, the researchers found that women in the experimental group found it more interesting than did women in the control group (Aronson & Mills, 1958). Women in the experimental group knew that they had paid a steep price to join the group ("I read all that lurid pornography out loud!"), but that belief was inconsistent with the belief that the discussion was worthless ("This discussion isn't interesting at all..."). As such, the women experienced cognitive dissonance, which they alleviated by changing their beliefs about the value of the discussion. We normally think that people pay for things because they value them, but as this study shows, people sometimes value things because they've paid for them. It is little wonder that some fraternities use hazing to breed loyalty, that some religions require their adherents to make large personal or monetary sacrifices, that some gourmet restaurants charge outrageous amounts to keep their patrons coming back, or that some men and women play hard to get to maintain their suitors' interest.
We desire consistency, but there are inevitably occasions when we just can't help but be unconsistent—for example, when we tell a friend that her new hairstype is "unusually trendy" when it actually resembles a wet skunk after an unfortunate encounter with a blender. Why don't we experience cognitive dissonance under such circumstances and come to believe our own lies? Because telling a friend that her hairstyle is trendy is inconsistent with the belief that her hairstyle is hideous, but it is perfectly consistent with the belief that one should be nice to one's friends. When small inconsistencies are justified by large consistencies, cognitive dissonance does not occur.
For example, participants in one study were asked to perform a dull task that involved turning knobs one way, then the other, and then back again. After the participants were sufficiently bored, the experimenter explained that he desparately needed a few more people to volunteer for the study, and he asked the participants to go into the hallway, find anothe rperson, and tell that person that the knob-turning task was great fun. The experimenter offered some participants $1 to tell this lie, and he offered other participants $20. All the participants agreed to tell the lie, and after they did so, they were asked to report their true enjoyment of the knob-turning task. The results showed that participants liked the task more when they were paid $1 than $20 to lie about it (Festinger & Carlsmith, 1959). Why? Because the belief that "the knob-turning task was dull" was inconsistent with the belief that "I recommended the task to that person in the hallway," but the latter belief was perfectly consistent with the belief that "$20 is a lot of money." For some participants, the large payment justified the lie, so only those people who received the small payment experienced cognitive dissonance. As such, only the participants who received $1 felt the need to restore consistency by changing their beliefs about the enjoyableness of the task. »