Hvorfor griner man?

Jeg vil bare give det et link:
http://en.wikipedia.org/wiki/Laughter

http://www.howstuffworks.com/laughter.htm

Og for de Dovne: :-)

Laughter is a part of human behavior regulated by the brain. It helps humans clarify their intentions in social interaction and provides an emotional context to conversations. Laughter is used as a signal for being part of a group — it signals acceptance and positive interactions. Laughter is sometimes seemingly contagious, and the laughter of one person can itself provoke laughter from others. 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.