Google Joke – Laughter, the intended human reaction to jokes is healthy. Laughter uses the stomach muscles, and releases endorphins, natural “feel good” chemicals, into the brain.
Jokes are only funny the first time they are told: once they are told the pattern is already there, so there can be no new connections, and so no laughter.
Jokes have an elaborate and often repetitive set up: The repetition establishes the familiar pattern in the brain. A common method used in jokes is to tell almost the same story twice and then deliver the punch line the third time the story is told. The first two tellings of the story evoke a familiar pattern in the brain, thus priming the brain for the punch line.
Jokes often rely on stereotypes: the use of a stereotype links to familiar expected behaviour, thus saving time in the set-up.
Jokes are variants on well-known stories (e.g. the genie and a lamp and a man walks into a bar): This again saves time in the set up and establishes a familiar pattern.