Creepy Study Shows How Much Babies Can Tell From Your Laughter

"Infants are sensitive to voices, and to particular tones of voices that signal positive affect."

Unsplash / Filip Mroz

Babies understand a lot more about what’s going on between adults than they get credit for, and new research suggests they can even tell whether you’re actually friends with someone — or just acting friendly toward a stranger. The scientists behind a new study published Monday in Scientific Reports found that babies could decode a remarkable amount of information from adults’ laughter.

In the paper, a pair of researchers describes how babies as young as 5 months old will pay closer attention to laughter that’s shared between friends than to laughter shared between strangers. The infants also seemed to be able to tell whether or not the sound of laughter matched the way two adults act toward each other. As early signs of social awareness, these babies’ behavior highlight just how much information laughter can reveal about human relationships, not to mention the fact that humans can apparently begin decoding this information at a very early age.

“These results provide the first evidence that infants can use a nonverbal vocal signal of affiliation in making social judgments as a third-party observer,” write Athena Vouloumanos,Ph.D., an associate professor of psychology at New York University, and Greg Bryant, Ph.D., a professor of communications at UCLA who specializes in “the evolution of vocal communication and social behavior.”

Check out this related video: Babies Laugh More Like Chimps Than Humans

This study consisted of two experiments:

Do They Laugh Like Friends or Strangers?

In the first experiment, 5-month-old babies watched a screen that showed an animated circle expanding (to hold their attention) while one of two audio tracks played: either friends laughing together or strangers laughing together. The babies listened for significantly longer to the recordings of friends laughing than they did to the recordings of strangers laughing.

Vouloumanos and Bryant argue that when the babies listen more intently to friends laughing, they’re showing us just how deeply wired humans are to perceive the subtle social cues that laughter conveys.

“Infants’ sensitivity to the social information in laughter by 5 months suggests early emerging, and possibly evolutionarily conserved, perceptual machinery for evaluating potential social signals that may be used to quickly draw inferences about the relationships between agents in the social environment,” they write.

Researchers showed that the sounds of friends or strangers laughing together are noticeably different.

Vouloumanos and Bryant

As previous research on social signals has suggested, humans are hardwired to read social cues to quickly determine whether someone is a friend or an enemy — something the researchers describe as “the relationships between agents in the social environment.” And while this skill might not always come in handy in contemporary society, this latest research shows that the instinct kicks in early in life.

The second experiment went on to demonstrate that babies can already match up their expectations with reality — all based on social cues.

Babies noticed when videos of people acting like friends (A) or strangers (B) didn't match up with the audio recordings of laughter.

Vouloumanos and Bryant

Why Are Friends Laughing Like Strangers?

In this experiment, the babies watched silent videos of two people either acting friendly or turning away from each other — accompanied by one of the two audio tracks from the first experiment. In this task, the babies watched significantly longer when the audio didn’t match the relationship shown on the screen.

Vouloumanos and Bryant say this result demonstrates that the babies notice a discrepancy between how people are acting and what they’re saying. In short, babies can not only tell the voices of friends from those of strangers, but also their actions. They argue that laughter conveys uniquely specific information about a relationship, information that babies are programmed to receive.

“Infants are sensitive to voices, and to particular tones of voices that signal positive affect and intentions to communicate (e.g., infant-directed speech, song) and, like adults may be able to use acoustic features in speech to infer social relationships,” they write.

“Infants’ sensitivity to different kinds of laughter might be one of the early emerging tools they use to understand and navigate the complex social world.”

Abstract: Colaughter — simultaneous laughter between two or more individuals — allows listeners across different cultures and languages to quickly evaluate affiliation within a social group. We examined whether infants are sensitive to acoustic information in colaughter that indicates affiliation, specifically whether they can differentiate colaughter between friends and colaughter between strangers. In the first experiment, infants who heard alternating trials of colaughter between friends and strangers listened longer to colaughter between friends. In a second experiment, we examined whether infants were sensitive to the social context that was appropriate for each type of colaughter. Infants heard colaughter between friends and colaughter between strangers preceded by a silent visual scene depicting one of two different social contexts: either two people affiliating or turning away from each other. Infants looked longer when the social scene was incongruent with the type of colaughter. By 5 months, infants preferentially listen to colaughter between friends and detect when colaughter does not match the affiliative nature of a social interaction. The ability to rapidly evaluate acoustic features in colaughter that reveal social relationships between novel individuals appears early in human infancy and might be the product of an adaptive affiliation detection system that uses vocal cues.
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