Human babies laugh like great apes, study says

Paris, 2 Sep 2021 (AFP) – “Huh-ha-huh!” instead of “ha ha ha!”. Like great apes, human babies laugh more by breathing in air, before evolving into a more communicative, adult laugh by breathing out more, according to one study.

The idea of ​​comparing man and animal in terms of laughter came up during a primatologist’s conference in Sicily, in the presence of a young researcher and friend of his.

This teacher showed how the laugh mechanism works among great primates (gorillas, orangutans, chimpanzees…).

The tickling sounds of these animals were emitted by inhaling and exhaling air, something like a “huh-ha-huh-ha”.

“My friend told me, ‘Well, my baby laughs like a monkey,'” recalls researcher Marishka Kret, a professor of cognitive psychology.

“She showed me videos of her son and the resemblance was evident! I immediately proposed to a vocalization specialist that we do a study,” he explained to AFP.

A team of experts in cognitive neuroscience, led by Kret with Diane Venneker at the University of Leyde in the Netherlands, carried out several experiments, the results of which were published on Wednesday in the Royal Society Biology Letters.

The researchers played recordings of human babies aged between 3 and 18 months to a first group of 15 phonetic experts and 102 (previously trained) newcomers.

Participants were to measure the proportion of inhalations and exhalations contained in sounds and then assess, on a rating scale, how pleasant and contagious laughter was for them.

Experts and novices came to the same conclusion: Younger babies’ laughter was 50% inhaling and 50% exhaling. An alternation of “huh” and “ha” very similar to that of non-human primates.

“Clearest sign”

Among adult humans, according to Mariska Kret, laughter is a product of 74% exhalation: they inhale and then utter some “ha ha ha” that gradually lose strength.

Experience has shown that as babies grow, the proportion of exhaled air increases and with it the positive perception on the part of the adult.

“This is what surprised us the most: to discover that a ‘mature’ laugh is perceived as more pleasant and contagious”, said the researcher.

Two additional experiments with new recordings and groups confirmed the finding: “ha ha ha” adults are more communicative.

“With exhalation, the signal seems clearer. The sound is not only louder, but also more controlled, which allows us to indicate to the interlocutor: ‘hey, this is fun!”, believes professor Kret.

Now it is necessary to clarify why babies go from “hu-ha-hu” to “ha ha ha”. One explanation would be that they poorly control their vocal abilities, which are progressively developed to gradually adapt to complex skills such as language.

And then there’s sociability. As the child grows older, he understands that he needs to learn to “laugh better” to make himself understood by his parents.

When there is laughter in the middle, social interactions last longer. And this also applies to primates.

“When monkeys laugh at an unexpected event, like a somersault, they show their hilarity, which is quickly imitated,” he explains.

But their vocal organs don’t evolve like those of human beings because they don’t speak. And so your laugh remains forever in a primal state, like that of a baby.