I once heard that the first rule of comedy is “If you have to explain it, it’s not funny.” I don’t think comedy can be explained, and lots of real life comedic moments lose something when explained.
It seems to me that, to be funny, a joke must take a moment for your brain to figure out. If it’s instantaneous, it’s not funny. If it takes too long, it’s also not funny.
How do we explain ethnic humor - which I still find funny;
I even find those jokes funny if I am the target.
Sadly its deemed okay to mutate those old jokes into “blonde” jokes, or some other “safe to make fun of” target.
My uneducated guess is that, at least for the funny ethnic jokes, the humour comes from the mental exercise of linking the action in the joke to the ethnic stereotype that’s being made fun of (ala Thudlow Boink).
The ethnic stereotype of the blond is that blonds are unintelligent and naive which happens to be the default ethnic stereotype.
I incline to the catastrophe theoretic explanation. One of the funniest ones I ever heard was totally spontaneous. I had an Israeli visitor staying with me temporarily until he found an apartment. There was a friend over and the Israeli was telling us about a group of Kurdish Jews who had their own synagogue, but it was located in some obscure place. Suddenly my friend burst out, “But the Kurds find their way.” This was so unexpected that I near fell off my chair laughing.
Another example. In 1964, my wife and I were sitting in a restaurant in Glasgow. In the next booth, I heard a Scot tell the joke, “What has four wheels and flies?” Now this joke is so old that even in 1964 it had grown hair, had it turn white and fall out. Nonetheless the answer floored us. “A corporation dustbin”. Again, total surprise.
Hearing, writing, and telling jokes makes you smarter. Builds neurological pathways between places that might not otherwise connect. Helps humans develop their puzzle-solving instinct by giving rewards for making unexpected connections, while in a safe environment (ie when it’s not physical danger.)
No, I don’t have a cite.
It seems easy enough to explain using your own theory. When is a fart not funny? When you’re in the middle of taking a shit (unless it’s abnormally loud, long, or wet). When is it funny? When performed in, say, a quiet library, or by Queen Elizabeth. We are expected to hold our farts in at times, and subverting this expectation is funny.
I hope I haven’t ruined farts for you.
Puns are the nicest form of humor because they don’t cause anyone pain. Except the audience.
I think this is largely it. Jokes can even be funny if you figure it out before the punchline. There’s a sketch by Mitchell and Webb that I still find funny even though I saw the joke coming well before the punchline, in fact I think it’s funnier because you can see it coming.
Except that you just did:
Farts are funny because they are totally unexpected, often even to the farter. We don’t expect our butts to make noise of their own volition and certainly not when it interrupts a conversation or dramatically silent moment. And then there’s not just noise, but often a particular acrid smell that lingers and from which no one can escape.
Farts subvert our calm, controlled reality; that’s why they’re funny.
Along these same lines, if you figure out the punchline before it gets delivered, the joke isn’t funny. You may appreciate its construction, but its no longer unexpected. It’s why obvious jokes don’t work, and why many are only funny once.
I think that you get a yes-no at the same time in your head that makes something funny
The Mitchell and Webb sketch that Richard Pearse linked to seems to be an exception. I thought I knew the punchline about 30 seconds in, and was certain at the 1:30 mark, and yet it was still funny. I’m not sure why–maybe because we hope the punchline will be something else, that there will be something that changes the outcome–and yet there isn’t. It’s almost as if the subversion of expectations is that they went with the obvious punchline after all. Or maybe it’s just good delivery.
I would suggest the reason it is funny is that we are primed for the come comeuppance of Mr Brain Surgeon. So the punchline, although signalled well ahead, is not the release we get, the release is the satisfaction of seeing its delivery. Had Brain Surgeon not been played as such a pr*ck, it would not have been funny. I could imagine the same sketch on stage and having Mr Rocket Scientist engaging the audience, bringing them along with its delivery. They would all know the punchline - the actor could turn to the audience and gesture them to deliver the words. It would still be funny, perhaps even more so.
This is a different sort of humour. It isn’t the joke that matters, it is a vehicle for a situational humour, one of interpersonal manners. The British make an art of comedy of manners.
Except fetuses with butts. Those are funny.
I was only considering the timing angle. If people only laughed at unexpected punchlines, Henny Youngman performances would be as silent as a tomb.
And it is energy also. Lenny Bruce did “Christ and Moses” in the Carnegie Hall Midnight Concert, and it is great . I laugh at “what are we paying protection for, anyway,” every time. But I got this massive CD set of scraps of concerts, and it has a couple of versions of this during his last years. Same material, but his timing is off, it has no energy, and it is awful.
I like watching MST3K and some of the jokes are based on cultural references. It seems like the more obscure the reference is the funnier the joke is. Maybe the humor is “I’m smart because I understand the reference”.
And ethnic humor and put-downs are funny becuase it’s telling us that we are better than them.
And the brain surgeon is really two parts. One is it’s funny because we are smart enough figure out the punch line before they get to it. Then when they do tell the punch line it’s the confirmation that we are smart.
I thought that was the best so far in the thread! 
It’s difficult to know just why, but I think some of the elements include, obviously, the unexpected twist at the end, but also, the idea of two renowned detectives being the victims of really brazen petty theft, Holmes’ ridiculously incongruous methodological approach to the discovery, and Watson’s idiotic obliviousness to the whole thing. The idea of people behaving very stupidly has been a staple of comedy forever, but it’s hard to do well. There generally has to be something incongruous about it.