By Megan Marples, CNN
Laughter transcends all languages — and now scientists know this spontaneous response is universal across some primate species, too.
The laughing patterns of human infants match those of great apes, according to a study published Tuesday in Biology Letters.
Human adults primarily laugh while exhaling, whereas infants and great apes laugh during both inhalation and exhalation, said study author Mariska Kret, associate professor of cognitive psychology at Leiden University in the Netherlands.
First adults inhale, then produce “ha-ha-ha” sounds in short bursts, starting loud and then fading away, Kret said.
“The ape-type is more difficult to describe but there is an alternation huh-ha-huh-ha,” she added.
Infant laughter isn’t necessarily similar to that of all species of great apes, just those that are evolutionarily closest to human — such as chimpanzees and bonobos, said Marina Davila-Ross, a reader in comparative psychology at the University of Portsmouth in England, who was not involved in the study.
“It seems to reflect that laughter is to some extent biologically deeply grounded,” she said.
Kret originally discovered this phenomenon while attending a talk by renowned primatologist Jan van Hooff with a friend. When van Hooff said apes laugh during inhalation and exhalation, Kret’s friend showed a video of her baby laughing in the same manner.
To test whether infants laugh like apes, Kret collected audio clips of humans ages 3 months to 18 months old laughing and asked listeners to rate what percentage of the laugh was produced by inhaling versus exhaling.
As a control, researchers also included five clips of adults laughing.
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