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Laugh, and the World Laughs With You

Laughing chimps tell us something about the evolution of speech.

Human language hasn’t simply replaced the vocalizations of our primate cousins. Instead, we use language on top of the communication systems we inherited from our prelinguistic predecessors. We laugh with joy, cry with despair, shriek with terror, shout with anger. And when we’re overcome with emotion, our language faculty shuts down altogether, leaving us with only our primal calls and facial expressions.

Our close cousins the chimpanzees have somewhat different body forms from ours, so they don’t share all of our vocalizations and facial expressions, and they even have some we don’t. But laughter is one emotional expression that’s uncannily similar in humans and chimps.

Human laughter isn’t just the fare of comedy clubs and late-night TV. Rather, it’s an integral part of our social communication. We laugh so frequently and so automatically that we’re often but vaguely aware we’ve done so and have little idea why we did. In fact, our intuitions about why we laugh are often wrong.

Most of the time when we laugh, we do so not because someone said something funny, but simply because they said something, and we’d like them to say more. We laugh to say, “I like you.” In other words, it’s a kind of social vocalization, not that much different from the mooing of cows in a herd.

Laughter evolved from the labored breathing of rough-and-tumble play, but it’s come to mean playful intent in both chimpanzees and humans. We punctuate our conversations with laughter, and by doing so, we encourage our conversation partner to stay in the chit-chat game.

Chimpanzees likewise use short bursts of laughter during social interactions, and they mimic the laugh patterns of those they’re engaging with, presumably to promote social cohesion. In other words, both humans and chimpanzees use laughter as a tool for building friendships.

Laughter is also a part of the mate attraction process in humans. By far, women do most of the laughing, and men do most of the laugh getting. Human females laugh more in the presence of males they find attractive. The more a woman laughs during an encounter with a man, the greater her reported interest in him. Little wonder then that women often say they’re looking for a man with a good sense of humor in their dating profiles.

(As far as I know, the question of whether female chimpanzees use laughter to signal sexual interest is still an open topic for research. But if you know of research on this subject, please leave citations in the comments.)

Laughter and language bear an interesting relationship. Each involves the same vocal apparatus, and so you can’t do both at the same time, even though they’re almost always used in the same context. Instead, we alternate between talking and laughing in conversational interactions, using laughter as a sort of punctuation between phrases and sentences. Even listeners usually wait until the end of the speaker’s sentence to laugh.

While it’s highly unlikely that language developed out of laughter, differences in the way humans and chimpanzees laugh suggest something about what was needed for language to evolve. When chimpanzees laugh, they produce one “ha” per breath. If you’d like to see and hear what chimpanzee laughter is like, check out these YouTube clips here and here.

Humans, however, have much greater control over their breathing, which is essential for producing speech. As a result, when we laugh, we typically produce a series of short bursts—“ha-ha-ha”—with each breath. Incidentally, human babies laugh like chimpanzees, with one “ha” per breath. But as they gain the breath control needed for speech during their first year, their laughter shifts to the typically human multiple “ha”s per breath.

Links between laughter and language show that we can’t have a complete understanding of how and why language evolved without fully considering the social functions it fulfills.

References

Davila-Ross, M., Allcock, B., Thomas, C., & Bard, K. A. (2011). Aping expressions? Chimpanzees produce distinct laugh types when responding to laughter of others. Emotion, 11, 1013–1020.

Mehu, M., & Dunbar, R. M. (2008). Naturalistic observations of smiling and laughter in human group interactions. Behaviour, 145, 1747–1780.

Palagi, E., & Mancini, G. (2011). Playing with the face: Playful facial “chattering” and signal modulation in a monkey species (Theropithecus gelada). Journal of Comparative Psychology, 125, 11–21.

Provine, R. R. (2004). Laughing, tickling, and the evolution of speech and self. Current Directions in Psychological Science, 13, 215–218.

Vettin, J., & Todt, D. (2005). Human laughter, social play, and play vocalizations of non-human primates: An evolutionary approach. Behaviour, 142, 217–240.

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