What makes you laugh? Being tickled, jokes, slapstick comedians - but why? We don't really know, although researchers in California have found the part of the brain that may be responsible. The doctors were performing brain surgery on a 16-year-old girl, for epilepsy. Every time a small area at the front of her brain was electrically stimulated, she burst out laughing. The girl always came up with a reason for her mirth - 'You guys are just so funny!'.