Cognitive dissonance has become one of those scientific terms that everyone knows and uses so freely and loosely that its original meaning has been obscured. We speak of cognitive dissonance when we find our glasses in the kitchen instead of the bedroom, when oestrogen replacement turns out to be unhealthy rather than healthy, whenever we are less than pleasantly surprised. In Leon Festinger's original theory, cognitive dissonance arises when a person is forced to entertain two mutually inconsistent ideas, which creates an unpleasant tension that motivates the person to engage in various mental gymnastics to minimize the dissonance, usually by denying one of the inconsistent cognitions. Elliot Aronson, Festinger' s most distinguished student, showed that cognitive dissonance is most common and most excruciating when new information is inconsistent with one's concept of oneself as an honest, intelligent and well-meaning person, and that the urge to maintain a favourable self-conception usurps all other possible strategies for escaping the dissonance. Cognitive dissonance can be as immediate and powerful as the response to physical danger.
Ellsworth, Phoebe C. "Enhanced Views." Review of Mistakes Were Made (But Not By Me), by C. Tavris and E. Aronson. Times Literary Supplement, no. 5478 (2008): 30.