From The New York Times:
So there are these two muffins baking in an oven. One of them yells, “Wow, it’s hot in here!” And the other muffin replies: “Holy cow! A talking muffin!” Did that alleged joke make you laugh? I would guess (and hope) not. But under different circumstances, you would be chuckling softly, maybe giggling, possibly guffawing. I know that’s hard to believe, but trust me. The results are just in on a laboratory test of the muffin joke.
Laughter, a topic that stymied philosophers for 2,000 years, is finally yielding to science. Researchers have scanned brains and tickled babies, chimpanzees and rats. They’ve discovered something that eluded Plato, Aristotle, Hobbes, Kant, Schopenhauer, Freud and the many theorists who have tried to explain laughter based on the mistaken premise that they’re explaining humor.
Occasionally we’re surprised into laughing at something funny, but most laughter has little to do with humor. It’s an instinctual survival tool for social animals, not an intellectual response to wit. It’s not about getting the joke. It’s about getting along.
More here.