“Huh-ha-huh!” vs “ha-ha-ha!”: Like great apes, human babies laugh a lot on inspiration, before evolving into a more expiratory, more communicative adult laugh, according to a study.
The idea of comparing humans and animals in this unusual field emerged during a conference given by a primatologist in Sicily, in the presence of a young researcher and her friend.
This teacher showed how laughter, which we now think is not specific to the human species, worked in great apes (gorillas, orangutans, chimpanzees…): the sounds, provoked by tickling, were emitted both by breathing in and out of air, similar to a “huh-ha-huh-ha”.
“My friend then told me + well, my baby is laughing like a monkey +,” recalls researcher Marishka Kret, professor of cognitive psychology. “She showed me videos of her son, the resemblance was obvious! I then asked a fellow vocalization specialist to do a study with me,” she told AFP.
A team of researchers in cognitive neuroscience, which she leads alongside Diane Venneker at the University of Leiden in the Netherlands, is developing several experiments, the results of which appeared Wednesday in the Royal Society Biology Letters.
To a first group of 15 phoneticians and 102 novices (previously trained), they played recordings of the laughter of human babies, aged 3 to 18 months.
Participants had to measure the proportion of inhalations and exhalations contained in the sounds, and then rate, on a rating scale, the extent to which they found these little laughs pleasant and contagious.
Experts and non-experts alike came to the same conclusion: the youngest babies’ laughter was produced 50% by inspiration and 50% by expiration. An alternation of “huh” and “ha” near non-human primates.
– “a clearer sign” –
In human adults, on the contrary, explains Mariska Kret, 74% of the laughter passes through the exhalation: they take a deep breath before coming out of the less and less loud “ha-ha-ha”.
Experience has shown that the older the babies were, the more the exhalation rate increased… and the more the adult’s perception was positive.
“That was what surprised us the most: to discover that a more mature + smile was perceived as more pleasant and more contagious”, says the researcher.
Two subsequent experiments, using a new group of participants and new recordings, confirmed that “ha-ha-ha” was more communicative.
“With expiration, the signal appears clearer. The sound not only gets louder, but also more controlled, which makes it possible to mean it to the other person + hey, that’s funny, let’s keep going! +”, analyzes Pr Kret.
It remains to be understood why children go from “hu-ha-hu” to “ha-ha-ha”. One of the explanations would be that their vocal apparatus, poorly mastered at the beginning, gradually develops to adapt to complex faculties such as language.
Another suggestion: as socialization increases, the young child learns to laugh better to be more responsive to parents, says the researcher.
Because social interactions have been shown to last longer if there is laughter, and that it is shared. It works as a social link, and not just in humans: “when great apes laugh at unexpected events, like a somersault, they display a playful air that is easily imitated”, emphasizes .
Gorillas play more and more often if they have shared a laugh, as the work of Italian ethologist Elisabetta Palagi shows, the researcher continues.
But probably because they are not able to speak, their vocal organ evolves differently and monkeys laugh all their lives like babies.