Hahaha

Laughing is an involuntary reaction to certain external or internal stimuli. Laughter can arise from such activities as being tickled,[1] or from humorous stories or thoughts.[2] 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 ("nervous laughter") or courtesy laugh. Factors such as age, gender, education, language, and culture are determinant factors[3] as to whether a person will experience laughter in a given situation.

Laughter is a part of human behavior regulated by the brain, helping humans clarify their intentions in social interaction and providing an emotional context to conversations. Laughter is used as a signal for being part of a group — it signals acceptance and positive interactions with others. Laughter is sometimes seen as contagious, and the laughter of one person can itself provoke laughter from others as a positive feedback. This may account in part for the popularity of laugh tracks in situation comedy television shows.

The study of humor and laughter, and its psychological and physiological effects on the human body, is called gelotology.

Children are said to laugh a great deal more than adults: an average baby laughing 300-400 times a day compared to an average adult laughing only 15-20 times a day;[citation needed] however the cited article, written by one of the two top humor researches in the world, establishes that there is no real basis for this claim.[5] Laughter might be thought of as an audible expression or appearance of excitement, an inward feeling of joy and happiness. It may ensue from jokes, tickling, and other stimuli completely unrelated to psychological state, such as nitrous oxide. One group of researchers speculated that noises from infants as early as 17 days old may be vocal laughing sounds or laughter,[6]