According to a study published Tuesday in Biology Letters, the laughing patterns of human babies match those of great apes.
Human adults laugh mostly while exhaling, while babies and great apes laugh during inhalation and exhalation, said study author Mariska Kret, an associate professor of cognitive psychology at Leiden University in the Countries. Low.
First the adults inhale, then produce “ha-ha-ha” sounds in short bursts, starting loud and disappearing, Kret said.
“The ape type is harder to describe, but there’s an alternation huh-ha-huh-ha,” he added.
Childhood laughter is not necessarily similar to that of all species of great apes, but to those that evolve closer to humans, such as chimpanzees and bonobos, said Marina Davila-Ross, a reader of comparative psychology at the University of Portsmouth. , in England. , who did not participate in the study.
“It seems to reflect that laughter is, to some extent, biologically deeply grounded,” he said.
Kret originally discovered this phenomenon while attending a talk by renowned primatologist Jan van Hooff with a friend. When Van Hooff said the monkeys laughed during inhalation and exhalation, Kret’s friend showed a video of his baby laughing in the same way.
To check if children were laughing like monkeys, Kret collected audio clips of people aged 3 months to 18 months laughing and asked listeners to rate what percentage of the laughter occurred by inhaling versus exhaling.
As a control, the researchers also included five clips of laughing adults.
After two rounds that included at least 100 listeners each, the results came. People could say that babies laughed at the same time inhaling and exhaling, while adults laughed mainly exhaling.
To ensure that the results were accurate, Kret had expert listeners analyze the sound bites and their findings aligned with those of the novices.
Exhaling laughter is more contagious
The researchers also assessed listeners that the sounds were the most pleasant and contagious.
The results showed the more laughter occurred when exhaling, the more people perceived it as positive.
The researchers confirmed this finding when they conducted another experiment and asked a new group of listeners to rate how positively they perceived laughter without being informed of respiratory patterns. The new group also found the exhaling laughter to be more enjoyable.
The laughter produced by the expiration tends to be louder and more controlled, noted Kret, who said it makes it easier for children to communicate that they are having fun and want to keep playing.
Older babies caused more exhaling laughter
The older babies in the study also produced more exhalant laughter than the younger ones.
This could be because, as babies grow, they learn “their communicative function and parents see that the baby is actively trying to make something clear,” Kret said.
Davila-Ross said she was surprised to see that the airflow associated with laughter changes as babies grow.
“It would actually be very interesting to see if these changes can also be found for other nonverbal vocalizations of humans,” he added.
In future research, Kret said he hopes to repeat his experiment with other vocalizations such as crying.
He is currently conducting other experiments on laughter, including one that includes orangutans, gorillas, and humans to see if they change the sound of their laughter to mimic the laughter of those around them.