New research suggests that a baby’s laugh is more similar to that of a chimp than of an adult.
A new study from a team at the University of Amsterdam (The Netherlands) has shown that a baby’s laughter bares a closer resemblance to the laugh of monkeys rather than of adults. Unlike adult laughter, babies laugh as they both inhale and exhale in a manner similar to non-human primates.
The study involved 102 students who evaluated sound clips taken from 44 laughing infants, aged between 3 and 18 months. The students evaluated each sound clip, determining the extent to which the laughs were produced on the inhale versus the exhale.
It was found that the youngest babies laughed on both the inhale and exhale, though as they got older it was predominantly produced on the exhale. Though there is no accepted reason as to why humans are the only primates that solely laugh on the inhale though it is suggested to be due to the vocal control that develops when learning to speak. However, the change doesn’t appear to be linked to any particular developmental milestones.
"Adult humans sometimes laugh on the inhale but the proportion is markedly different from that of infants' and chimps' laughs. Our results so far suggest that this is a gradual, rather than a sudden, shift," commented Disa Sauter, a researcher on the study.
The results are currently being checked by expert phoneticians to reaffirm the results collected from students. The ultimate goal is then to use these results to give insight into vocal production in children with developmental disorders. “If we know what normally developing babies sound like, it could be interesting to study infants at risk to see whether there are very early signs of atypical development in their nonverbal vocalizations of emotion” added Sauter.
The results were presented at the 179th meeting of the Acoustical Society of America, in conjunction with the Canadian Acoustical Association’s 2018 Acoustic week (5–9th November 2018, Victoria, BC, Canada).