Scientists have found that the laughing patterns of human babies match those of great apes.
A study published in the Biology Letters journal on Tuesday found that infants’ laugh patterns were more similar to chimpanzees than grown-up humans. Throughout their upbringing, they slowly learn to develop a laughing pattern like their elders.
When adults laugh, they first inhale and produce “ha-ha” sounds in short bursts, which are louder to begin with and eventually fade away, study author and associated professor of cognitive psychology at the Netherlands’ Leiden University, Mariska Kret, said.
“The pattern we see in young babies is very close to what we see in our closest living [primate] relatives,” said Kret.
When apes laugh, they tend to produce laughter noises as they inhale and when they exhale too.
“The ape-type is more difficult to describe but there is an alternation huh-ha-huh-ha,” she said.
Scientists conducting research on the matter have found that the laughing patterns of infants that are under 18 months old more closely resemble those of apes, since babies laugh during inhalation and exhalation.
Infant laughter is apparently not necessarily similar to that of all ape species but mainly those that possess evolutionary characteristics similar to humans, such as chimpanzees and bonobos, Marina Davila-Ross, a reader in comparative psychology at the University of Portsmouth in England, who was not involved in the study, told the CNN.
“It seems to reflect that laughter is to some extent biologically deeply grounded,” she said.
The study involved collecting audio clips of humans aged three to 18 months old laughing and then asking listeners to rate which percentage of the laughs were produced during inhalation and exhalation. They also included audio recordings of five adults laughing, to ensure greater accuracy and credibility.
Exhaling laughter is more contagious for humans
The researchers of the study also found that exhaling laughter was more contagious. Listeners involved in the study rated the sound as more positive.
They then conducted another experiment with a new group of listeners to rate how they perceived the laughter, without informing them of the breathing patterns involved in the audio recordings. The new groups also found exhaling laughter to be more pleasant.
Laughing patterns produced by exhaling tends to be louder and more controlled, said Krent, making it easier for babies to communicate that they are happy or having fun and want to continue playing.