Laughter

Laughter is a pleasant physical reaction and emotion consisting usually of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter can arise from such activities as being or from humorous stories or thoughts. Most commonly, it is considered an auditory expression of a number of positive emotional states, such as joy, mirth, happiness, or relief. However, it can also be caused by opposite emotional states such as embarrassment, surprise, or confusion, such as nervous laughter or a courtesy laugh. Age, gender, education, language, and culture are all ^factors in determining whether a person will experience laughter in a given situation. Some other species of primate (chimpanzees, gorillas, and orangutans) show laughter-like vocalizations in response to physical contact such as wrestling, play chasing, or tickling.