Laughter is a rhythmic physical and vocal reaction to humor or to a number of other stimuli. A stimulus (plural, stimuli) is something that provokes a reaction. People may laugh in response to something seen or heard that they find amusing. People may also laugh in other circumstances, such as when they feel embarrassed or uncomfortable. Laughter has long been considered a behavior unique to humans. However, scientists have found that other animals, such as chimpanzees, also laugh. This article focuses on laughter in humans.
Laughter occurs in a wide variety of forms, but most of them include both gestures and vocal sounds. When a person laughs, facial muscles contract to open the mouth or form a smile. The person may throw the head back. The larynx (voice box) contracts, and involuntary spasms of muscles used in breathing cause the person to audibly gasp or exhale. Heavy or continued laughter often activates the tear ducts, leading to the appearance of crying. Laughter may also stimulate the release of endorphins, chemicals in the brain that produce a sensation of well-being.
Laughter is most often produced by humor. Surprise, incongruity (the putting together of unrelated things), and human folly are all sources of humor that can cause laughter. Physical humor—such as falling or narrowly avoiding serious injury—is among the most basic causes of laughter. People also tend to laugh at wit or cleverness. See Humor .
Laughter serves many social purposes. People generally laugh more often when with others than while alone. At a party, people might laugh to join in the fun, to show that they appreciate a joke, or to flirt. Employees may laugh at a boss’s bad joke to appear agreeable. People may also laugh joyfully when seeing someone they love after a long absence. However, laughter is not always positive or joyful. It may arise from anxiety, a desire to please, or a need to put ourselves and others at ease. People also laugh because they are tired or stressed or when someone they dislike is mocked.
Excitement, stimulation, and lowered inhibitions make people more likely to laugh. Certain chemicals, such as nitrous oxide, can stimulate laughter. Mental illness or other brain disorders may cause uncontrolled laughter. But in healthy people, laughter is a normal, wide-ranging, nonverbal emotional response.
See also Comedy .
