When I was an undergraduate, I came up with an idea about why people laugh: Laughter is triggered by sudden pleasure. Not pleasure alone, it must increase quickly. Sudden pleasure is the necessary and sufficient condition for laughter. The threshold goes up and down — easier to make someone laugh if they’re nervous or cold, for example — but the basic rule never changes. (Tickling is an exception, of course.) Two old friends unexpectedly encounter each other, they embrace, laughing.
Humor is a subset of what causes laughter. Obviously we enjoy humor and jokes have punchlines — the necessary conditions are met. Maybe humor can tell us something about evolution: What is funny reveals what we enjoy, which may have a genetic basis.
I figured out that many jokes derive their pleasure from more than one source. These sources include:
1. Something forbidden. We have something we want to say or would enjoy saying; humor lets us say it.Insults, sexual stuff, scatological stuff (for children), swear words. Political jokes, a much bigger deal in the former Soviet Union than in America, tell forbidden truth about the government.
2. Something clever. Connecting two things that are quite different.
3. Something incongruous. Many New Yorker cartoons involve animals talking or children talking like adults.
Many jokes are clever insults, for example. Maybe the “did somebody say something” joke that I was puzzled about is an example. The speaker is saying “I don’t care about what you care about” (an insult of sorts) in a clever way.
I suspect this list is incomplete — but now that I’ve made it I can test it.