Laughter is a physical reaction in humans and some other species of primate, consisting typically 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
tickled, or from
humorous stories or thoughts. Most commonly, it is considered a visual expression of a number of positive emotional states, such as joy, mirth,
happiness,
relief, etc. On some occasions, however, it may be caused by contrary emotional states such as embarrassment, apology, or confusion such as
nervous laughter or courtesy laugh. Age, gender, education, language, and culture are all factors as to whether a person will experience laughter in a given situation.
