Hard SF : Aliens : Humor?
Timing is very important in humor. But timing in what? First, perhaps it's necessary to divide humor into separate categories. If we laugh at someone being hit in the face with a pie, perhaps timing isn't so important. But when we listen to a joke, there seems to be a matter of timing in how long it takes us to "get it".
Somebody asks you, "How many Martians does it take to change a light bulb?" You say, "How many?" He gives you the punchline: "Three! One to hold the light bulb and two to turn the ladder!" If you find it funny, it's because it took you just the right amount of time to figure out: that the Martians are changing a light bulb in a ceiling fixture which requires getting up on a ladder to reach, but they are too dumb to simply have the Martian on the ladder twist his hand to tighten the bulb into place. Therefore, the Martians have used the much less efficient method of having the Martian on the ladder stand perfectly still while two Martians standing on the floor hold the ladder and walk in a circle so the ladder rotates around the axis of the ceiling fixture until the bulb is tight.
Reading this elaborate explanation of a joke, of course, kills any humor value. Enjoying a joke requires figuring it out yourself in a short period of time. I imagine this is because figuring it out quickly makes the listener feel smart.
If you'd never seen or heard of a ceiling light fixture for light bulbs, you wouldn't know what a ladder had to do with changing a light bulb. You'd have no idea what they were doing. You wouldn't find it funny. Once someone explained it to you, you'd understand but you wouldn't be amused.
A joke that is too obvious isn't funny because you can't really feel clever about figuring it out. A joke that takes too long to figure out, even if nobody has to explain it to you, isn't funny either.
At least in humans, there is a link between humor and one's perception of one's own intelligence. It seems reasonable that in the evolution of intelligent species they will develop a psychology that promotes putting a value on intelligence. If that is true, self-appreciation of one's own intelligence may lead to something like humor in others. If not the equivalent of laughter, at least the equivalent of a grin of pride.
One could test one's intelligence by exchanging brain-teasers rather than jokes. However, probably not as the most common form for a species. While everybody wants to think they are clever, not everyone is really good at brain-teasers. What the average person needs is something which is not too hard. For a joke to be funny, you have to "get it" within a second or two. At least for humans, this seems to express an evolutionary appreciation of intelligence that doesn't require a whole lot of research or calculation. That makes sense, early humans living in the wild probably had to value snap decisions in cases of danger and a person's memorization of the means of a hunter-gatherer lifestyle. On this level, a joke could be brain exercise.
Human jokes tend to have other elements. I'm not sure how much sex tends to be a common element in jokes because it is a topic with social inhibitions, and how much it reflects the importance of reproduction to living creatures. In favor of the first explanation is the widespread nature of other kinds of "toilet humor" which may reflect necessary body functions, but not ones that are at the level of DNA's demand to copy itself as much as possible. If sex is a common humor element because of social inhibitions, it's not so clear whether it would be common in extraterrestrial humor.
Another common element in humor is making fun of "them". You don't tell light bulb jokes about "us". This may partly be no more than another way to say "I am clever" or "We are clever", with the others portrayed as dumb only as contrast to highlight how smart we are. On the other hand, humans may really care about the fact "'they' are dumb". We may have a deep-seated "us vs. them" psychology. It is reasonable for evolution to give us a perspective that makes us prefer, protect and promote our own corner of the gene pool. If individuals of an intelligent species are molded to favor those closest to their own combination of genes, they will to one degree or another disfavor those with less similar genes. If humor (or parallel forms) are used by intelligent species to say "I am clever", it may be common to use the same form to express "they are not clever".
(But it's not a joke to say: "These Martians were so dumb they couldn't figure out to twist their wrists to change a light bulb. So they had one guy stand on a ladder while two guys turned the ladder." Saying "they are dumb" is only funny if you have to "get the joke".)
Somewhere, a comedian may be asking an audience, "How many Earthlings does it take to change an illuminator? [Pause] None! They're still using [pause, snicker] light bulbs!"