The ability to tell the nature of social relationship between people is introduced early in human infancy, a new study has revealed.
Babies as young as five months old have been found able to distinguish laughter between that of friends and strangers.
The study carried out by researchers at New York University and University of California, Los Angeles (UCLA) discovered that the infants sensitivity to different kinds of laughter might be used to comprehend and navigate the complex social world.
Recently, it has been established that laughter between two or more people can give a third party listeners (adults) a quick evaluation of the nature of the relations between the individuals: are they strangers, acquittances or friends?
“Instances of shared laughter can give out a lot of information about people’s relationship, detectable in babies as young as five months old and universally by grown up individuals across the world,” says Gregory Bryant, a professor in UCLA Department of communication.
In the research published in the journal Scientific Reports, the experts examined how five-month-old babies processed exchanges of co-laughter between friends and strangers by measuring how long they listened to the laughing sounds in two different experiments.
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In the first experiment, the infants were made to listen to alternating audio recordings of laughter between friends and strangers. The babies listened longer to the laughter between friends.
This revealed that the infants not only could differentiate between the two laughters, but when given a choice, they preferred the friends laughing audios.
In the second experiment, the researchers linked visual images of friends and strangers to their laughing sounds too see if the little ones could link the co-laughter to judgements on human relationships.
The babies saw two video clips of actors interacting. In the first video, the actors were smiling at each other like they are friends and in the second one, they turned their backs to each other indicating they were strangers.
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The video was then paused on a still frame of the actors facing the babies with neutral expressions, then they heard alternating audio recordings of friends or strangers laughing.
Staring for a longer period of time is also used by babies to understand relationships, with a longer gaze evidence of surprise.
The researchers had anticipate that if the little ones recognized the social context that was right to each type of laughter, they would look longer when the laughter and social context were mismatched.
As expected, the infants looked longer when social interaction was incompatible with the type of laughter, indicating that they could match laughing audio that fit the depicted social relationships.
“The ability to rapidly evaluate acoustic features in colaughter that reveal social relationships between individuals appears early in human infancy and might be the product of an adaptive affiliation detection system that uses vocal cues,” concluded Athena Vouloumanos, an associate professor in NYU’s Department of Psychology and one of the co-authors of the study.
