Why do we laugh?
Most laughs follow ordinary remarks, not jokes. What overheard conversation, great ape calls and a 24-society listening study say about why we laugh.
Answer to the question
Why do we laugh?
Laughter is mainly a social signal, not a response to jokes. In Robert Provine's 1,200 overheard laughs, more than 99 percent fell at the end of a phrase, and fewer than a fifth followed remarks that were remotely funny. Research across great apes and 24 societies links laughter to play and closeness.
Key takeaways
- In Robert Provine's record of 1,200 overheard laughs, more than 99 percent fell at pauses at the ends of phrases or sentences.
- Steven Pinker reports that fewer than a fifth of the remarks before those laughs were remotely humorous, and that about half of people asked to laugh on command say they cannot.
- Acoustic analysis of tickle-induced calls in orangutans, gorillas, chimpanzees, bonobos and humans led Davila Ross, Owren and Zimmermann to propose a common origin for laughter.
- Robin Dunbar proposes that laughter, a modified play vocalisation, let early groups bond in larger numbers than grooming allowed.
- In 24 societies, 966 listeners judged friends from short clips of shared laughter above chance (Bryant and colleagues, 2016).
In 1,200 overheard laughs, more than 99 percent landed in the pause at the end of a phrase or sentence, where a speaker would breathe. Almost none cut across a word. Why do we laugh, then, if so little of it has to do with being amused?
Why we laugh at remarks that nobody would call funny
Robert Provine, a neuroscientist who spent years listening to ordinary conversation, took that pattern as a sign that laughter has priority over speech, behaving less like a reaction to a joke than like a punctuation mark. Provine's observers recorded what was said just before each laugh. Steven Pinker, who draws on that work in When Everyone Knows That Everyone Knows, reports that fewer than a fifth of those remarks were even remotely humorous. Most were everyday comments, the sort of line a person offers while greeting a friend or ending a sentence.
The same corpus showed that speakers laughed more than the people listening to them, which is the reverse of what a joke-and-reaction account would predict, since the audience is the party being amused.
Pinker also notes that about half of people asked to laugh on command say they cannot. That detail fits an old observation about the behaviour: laughter is not under easy voluntary control, and everyone present knows it. Pinker builds his argument on that point. A laugh is public, hard to fake and plainly audible to both parties, so it becomes something each person knows the other has noticed, the layered knowledge he calls common knowledge, set out in the vault note on Common Knowledge. On his account, a laugh tells a listener that something which could have read as a threat, a blunder or an insult is not meant that way, and that both people are aware of it.
The same idea explains why a laugh can follow a plain remark. It is a quick way of saying that the exchange is friendly, and the sender need not wait for anything funny to arrive. The vault note on Laughter as Group Bonding records the same reading from the observational side.
Laughter turns out to be older than speech and jokes
If laughter were a by-product of humour, it should be recent. The comparative evidence points the other way. Marina Davila Ross, Michael Owren and Elke Zimmermann analysed the sounds made when orangutans, gorillas, chimpanzees, bonobos and humans are tickled. When they compared the acoustic features across the five species, the resulting family tree matched the known genetic relationships among them. They concluded that the calls share a common origin and can reasonably all be called laughter, with two main periods of change within the great ape family, the second after the human line separated from the chimpanzee and bonobo line.
Robin Dunbar takes the story a step further. Among monkeys and apes, social grooming is the main way of keeping bonds in good repair, but it takes time and works with one partner at once. Dunbar proposes that early hominins used laughter, a modified play vocalisation, as a group form of bonding that let them hold together in larger groups than grooming allowed. He presents evidence that laughter triggers the brain's endorphin system and strengthens bonds among those who laugh together, and his reverse-engineering model places the human form of laughter at around 2.5 million years ago, in the genus Homo.
The appeal of the idea is its reach: grooming serves one partner at a time, while a laugh can be shared across a whole circle at once, so the same effort of bonding is spread over more people. It also gives the earlier findings a reason, since a signal built for groups would be expected to turn up in ordinary talk between friends and not only after jokes.
That origin in play matters for what we hear today. A play signal tells a partner that rough contact is not an attack, the idea explored in The Play Signal, and laughter in adult conversation can do the same work when a remark has an edge. Play draws onlookers as well as players, a pull examined in Why We Watch Others Play Games, and a shared laugh is one way a crowd joins in.
Hearing a laugh together tells outsiders who is close
A laugh carries information to anyone who hears it, including people outside the joke. Gregory Bryant and a large international team played short clips of two people laughing together to 966 listeners in 24 societies, and asked whether the pair were friends or recent strangers. Listeners judged friendship with above-chance accuracy.
The finding suggests why laughter spreads so readily among people who like each other. Hearing a laugh is hearing a claim about the relationship, and joining in is a way of confirming it. The pull is a close cousin of what researchers describe in What is emotional contagion, and the sense of being part of a group that follows is the subject of Why Do We Need to Belong. Provine's result that speakers laugh more than listeners fits too: the person talking is often the one setting the tone.
Put together, the studies give a few things anyone can watch for in daily life.
- Laughs tend to arrive at the end of a phrase, not in the middle of it.
- Many laughs follow remarks that nobody would call funny.
- People who are close tend to laugh together, and outsiders can often hear it.
None of these needs a laboratory. Next time a room fills with laughter, count how many jokes came first.
Common questions
Why do we laugh?
Laughter is mainly a social signal. In Provine's overheard conversations, most laughs followed ordinary remarks, not jokes, and they fell at phrase boundaries. Pinker's account is that a laugh tells others, openly, that something is not meant seriously.
Is laughter only a response to humour?
No. In the observational record fewer than a fifth of the remarks before laughs were remotely funny, and speakers laughed more than listeners.
Do other animals laugh?
Great apes make tickle-induced calls whose acoustic features line up with human laughter. Researchers who compared them proposed a common origin and called them laughter.
Can strangers tell when two people are friends from their laughter?
In a study across 24 societies, listeners judged friends from short clips of shared laughter with above-chance accuracy.
Sources
Pinker, S. When Everyone Knows That Everyone Knows. Seed book; vault hub Books/When Everyone Knows That Everyone Knows.
Provine, R. R. (1993). Laughter punctuates speech: Linguistic, social and gender contexts of laughter. Ethology, 95(4), 291-298. doi:10.1111/j.1439-0310.1993.tb00478.x https://doi.org/10.1111/j.1439-0310.1993.tb00478.x
Davila Ross, M., Owren, M. J., & Zimmermann, E. (2010). The evolution of laughter in great apes and humans. Communicative & Integrative Biology, 3(2), 191-194. doi:10.4161/cib.3.2.10944 https://doi.org/10.4161/cib.3.2.10944
Dunbar, R. I. M. (2022). Laughter and its role in the evolution of human social bonding. Philosophical Transactions of the Royal Society B, 377(1863), 20210176. doi:10.1098/rstb.2021.0176 https://doi.org/10.1098/rstb.2021.0176
Bryant, G. A., Fessler, D. M. T., Fusaroli, R., Clint, E., Aarøe, L., Apicella, C. L., et al. (2016). Detecting affiliation in colaughter across 24 societies. Proceedings of the National Academy of Sciences, 113(17), 4682-4687. doi:10.1073/pnas.1524993113 https://doi.org/10.1073/pnas.1524993113