The mental faculty of discovering, expressing, or appreciating the ludicrous or absurdly incongruous.
Sigmund Freud considered humor an outlet for discharging pent up psychic energy and diminishing the importance of potentially damaging events. Since the 1970s, research on humor has shifted from a Freudian focus to an emphasis on its cognitive dimensions, including investigations involving information-processing theory. Humor has been found to depend on the disparity between expectations and perceptions, generally termed "incongruity." Not all incongruity, however, is humorous; for humor to be evoked, the incongruous must somehow be meaningful or appropriate, and must be at least partially resolved. Research has shown the importance of humor both in social interaction and human development. Developmental psychologists consider humor a form of play characterized by the manipulation of images, symbols, and ideas. Based on this definition, humor can first be detected in infants at about 18 months of age with the acquisition of the ability to manipulate symbols. Some researchers believe that humor can be considered present in infants as young as four months old if the criterion used is the ability to perceive incongruities in a playful light and resolve them in some manner. Most research thus far has focused on responsiveness to humor rather than on its instigation, production, or behavioral consequences.
Humor serves a number of social functions. It can serve as a coping strategy, to cement allegiances, or to test the status of relationships. One of the main signs of a healthy ego is the ability to laugh at one's own foibles and mistakes. Humor can be used to lend social acceptability to forbidden feelings or attitudes, a phenomenon at least as old as the Renaissance fool or Court Jester who was given license to voice unpleasant truths and mock those in positions of authority. Research has also led to the view that humor is a way of countering anxiety by reasserting mastery over a situation. Feelings of help-lessness have been found to characterize both anxiety and depression. (One of the signs of depression is the inability to appreciate or use humor.) Humor gives people an opportunity to stand outside the dire aspects of a situation, however briefly, and assert a measure of control through the ability to laugh at their predicament. This dynamic, which drives the phenomenon known as "gallows humor," is expressed in the following witticism about two contrasting cities: "In Berlin, the situation is serious but not hopeless; in Vienna, the situation is hopeless but not serious."
Dix, Albert S. Humor: the Bright Side of Pain. New York, NY: Carlton Press, 1989.
Green, Lila. Making Sense of Humor: How to Add Joy to Your Life. Glen Rock, NJ: Knowledge, Ideas, and Trends, 1994.