Few things can delight an adult more easily than the uninhibited and effervescent laugh of a child. Yet, the child's laughter, as a new study demonstrates, differs from adult laughter in a crucial way: children laugh as they exhale and breathe both, in a way that is very similar to non-human primates.
The research will be described by Disa Sauter, psychologist and associate professor at the University of Amsterdam, in the Netherlands, during a speech at the 176th Meeting of the Acoustical Society of America, coinciding with the Canadian Acoustical Association 2018 acoustic week in Canada , November 5-9 at the Victoria Conference Center in Victoria, Canada.
Together with her colleagues, psychologist Mariska Kret and Ph.D. Dianne Venneker of Leiden University in the Netherlands, and Bronwen Evans, a phonetic at the University College of London-Sauter, have studied laughter clips from 44 newborns and infants among 3 and 18 months of age. Recordings were taken from online videos where children were involved in playful interactions. The recordings were then analyzed by 102 listeners, recruited from a student population of psychology, who assessed to what extent the laughter in each clip was produced on expiration with respect to inhalation.
Sauter and his colleagues found that younger children commonly laughed for both inhalation and exhalation, as well as non-human primates such as chimpanzees. In the older children studied, however, laughter was mainly produced only during expiration, as in the case of older children and adults.
"Adult humans sometimes laugh by inhalation, but the proportion is quite different from that of the chuckling and childrens' laughter: our results so far suggest that it is a gradual, rather than a sudden change," said Sauter, who emphasizes that the transition does not seem to be linked to particular development goals. He noted, however, that these results were based on the opinions of non-expert listeners. "We are currently monitoring those results against phonetic sentences, which are making detailed annotations of laughter."
Sauter said that there is no accepted reason why humans, alone among the primates, laugh only for the exhalation. One possibility, he said, is that it is the result of the vocal control that humans develop while they learn to speak.
Researchers are currently examining whether there is a link between the amount of laughs produced by inhalation and exhalation and the reasons why people laugh, which also change with age. In infants and younger children, as in non-human primates, rice occurs as a result of physical play such as tickling. In older individuals, laughter can derive from physical play but also from social interactions.
"In addition to this, I would be interested to see if our results apply to other vocalizations than to laughter," Sauter said. Ultimately, the research could provide information on the vocal production of children with developmental disorders. "If we know how the normally developing children play, it might be interesting to study at-risk children to see if there are very early signs of atypical development in their non-verbal emotional vocalizations."
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Presentation # 3aSC5, "How do the children laugh?" Disa Sauter, Bronwen Evans, Dianne Venneker and Mariska Kret will be on Wednesday, November 7 at 9:25 am in the SALON A of the Victoria Conference Center in Victoria, British Columbia, Canada. acousticalsociety.org/asa-meetings/