The scientific explanation for humor: Why do we laugh?

One of the theories behind humor is that it’s the body’s way of signaling that something is no longer threatening. It has to do with cognitive dissonance – the mental stress or discomfort experienced by an individual who holds two or more contradictory beliefs, ideas, or values at the same time or is confronted by new information that conflicts with existing beliefs, ideas, or values.” So we developed a sense of humor by perceiving a danger and later finding out that the threat was a misunderstanding. An example of this would be our ancestors being afraid of a loud noise in the woods and then discovering that it was caused by a tiny squirrel. Humor is a way in which the mind reconciles reality with its imagination, and thus closes the gap that is cognitive dissonance. This has evolved to include not just danger but other inconsistencies in reality. Most jokes have two story lines, a set up and a punchline. The set up leads you down one train of thought and plays to your sense of reality. The punchline creates a second parallel train of thought that reconciles your reality to your imagination. (It also works if the roles are reversed.) You are lead to believe one thought in the set up, then you find out that there is also a second hidden thought that you didn’t think of that you also believe to be true.


Humor and creativity are kind of weird aspects of human nature because they’re very difficult to account for under Darwin’s Natural Selection theory. Why are we creative? Why do we make jokes?

There have been a lot of different theories of this. Some people think they are mere side effects of human intellect (exaptations) and others think that they serve some sort of adaptive function (Social Brain hypothesis).

Geoffrey Miller has proposed that many of our cognitive functions are the result of sexual selection (another of Darwin’s theories, explored in The Descent of Man). This would propose that humor and creativity serve as honest indicators of quality in potential mates. For example, humor, creativity, and intelligence are all highly correlated. Or potential mates with less parasite resistance may not have the excess energy to expend on creative behaviors. Under this theory, creativity and humor would be displays, advertisements for mates.

It’s pretty interesting stuff. Ultimately it can be difficult to apply evolutionary theory to human culture and behavior rigorously. But if you’re interested in reading more about it Karmihalev’s (2013) review “Why Creativity is Sexy” is readily available online and unites a lot of the evidence in favor of Miller’s theory.


Some research has suggested that while females generally prefer a mate with a good sense of humor, males tend to prefer a mate that is receptive to humor (Bressler et al., 2006; Bressler and Balshine, 2006; Clegg et al., 2011). So uncontrollable bouts of laughter may be the appropriate response, advertising a preference for humor, which may make a mate more desirable. There’s no need for this to be restricted by sex, though, as humans are very monogamous and have likely been acted upon by sexual selection for both sexes, given our high parental investment. Or perhaps it’s a bit more Fisherian, with a correlated sex-limited trait and preference for humor that might lead to an expression of that trait in both sexes dependent on certain steroid and hormone levels.

As far as other animals go, there seems to be a correlation between intelligence and practically useless cognitive feats like humor and creativity. So I would guess there may be a threshold of intelligence that must be crossed for the expression of humor. There’s some evidence of a threshold for creativity around 100-120 IQ points (Jauk et al., 2013). I would guess that if humor is present in animals, it would be in social animals with high intelligence and high parental investment. Great apes are obvious, our closest ancestors. Might try dolphins and whales, too, though. But I don’t know what the literature says.


Sigmund Freud had a theory on this. Generally he identified humorous pleasure as the release of tension. The pleasure comes from having to exert less mental effort than expected.

Think of the scene in Annie Hall where Woody Allen sneezes on some cocaine and blows it everywhere. There is a release of tension, since prior to that moment, he is trying very hard to impress his friends. But when he sneezes, the tension is released, since he has failed to impress them. The viewer is no longer tense on Allen’s behalf.

An example Freud gives is some children putting on a play they have written, for an audience of adults. The play features a couple. The husband goes away to sea, and comes back several years later, having earned some money. The wife says “I too have not been idle,” and pulls back a curtain to reveal the children she has had. The audience laughs, because the implication is that the wife has cheated on the husband, but the children performing the play do not understand this. The children treat the apparent infidelity as no cause for concern, whereas to an adult it is the opposite. The difference between the amount of emotion an adult would expend in the depicted situation, and the amount of emotion the characters portrayed by the children expend, is treated by the audience as an economy, according to Freud. The audience does not have to exert any mental effort in simulating the emotion of the characters, or to empathise with that emotion, since the emotion is absent, and this saved effort is pleasurable.

This is discussed in Freud’s book Jokes and their Relation to the Unconscious.


Generally speaking, all hypotheses seem to think the original purpose was hi-jacked as a social communication device, even including sexual selection. That is, given an initial value to humor in terms of surviving or prospering in a group setting — regardless of what the actual source was — the resulting talent of a male to perform it became a means by which females selected males, much like a peacocks tales. That is, the ability of males to perform it and the ability of females to judge and differentiate on it would have co-evolved. This explanation comes from the sexually dimorphic status of humor. Across cultures and time, it is males who statistically perform more humor and females who judge it, seek it, and find it attractive. (Again, that’s statistical, like height. There are funny women and unfunny men, men who find it attractive in women, etc. But there is a significant statistical difference in how men and women approach it.)

One of the origins theories separates two types of humor: the “funny” kind (Duchene) and the “awkward” kind (non-Duchene). Gervais and Wilson suggest that the funny kind may have evolved as a social signal that some specific novelty was not a danger, but was an opportunity to explore it an learn. This would correspond to why humor is typically about some sort of novelty or something unexpected, like a new way of looking at things.

Under their work, the “awkward” kind (non-Duchene) appears to have evolved later as an attempt to mimic the appearanceof humor and laughter, but in a forced way like responding to a surprise/prank or a social response to somebody telling a cute story without any actual humor in it per se. (For a layman’s discussion, see here.)

There are variety of other theories. For a review, try (Polimeni and Reiss, 2006)[]. They are categorized as incongruity theories, expression of sexual or aggressive feelings, and demonstration of superiority. Others (see here) include benign violation theory, the mechanical theory, and release theory. I find these latter hypotheses are more about categorizing types of humor and may propose a value with that given type. But they don’t seem to describe theexistence of humor.

The Gervais and Wilson hypothesis does have a plausible explanation of the origins in terms of natural selection value, and sexual selection and cultural hi-jacking hypotheses also fit available data. But, I would not say these are anywhere near clearly demonstrated or sufficiently detailed. Plausible, yes, but not even close to a done deal.

One Comment to The scientific explanation for humor: Why do we laugh?

  1. thanks for this post I really enjoyed it

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