Study: Why Do Babies Smile? To Get Smiles In Return

A new study has discovered that babies time their smiles so that people will keep smiling at them.

Researchers from the University of California, San Diego have discovered that babies do have a purpose behind their irresistible smiles—to get more smiles from the person they are interacting with.

“If you’ve ever interacted with babies, you suspect that they’re up to something when they’re smiling. They’re not just smiling randomly,” said Javier Movellan, a research scientist in the Machine Perception Laboratory at UC, San Diego, and one of the study’s authors via a press release. “But proving this is difficult.”

Movellan and his colleagues proved that indeed babies don't smile for nothing. In the study published in the journal PLOS ONE, researchers used an approach that has never been used before. Combining developmental psychology, computer science, and robotics, they have arrived at the conclusion that babies use sophisticated timing mechanisms to maximise people's responses to their smiles, while actually doing so little.

Researchers used data from a previous study that observed the face-to-face interactions of 13 pairs of mothers with their babies under four months, indicating when and how often both parties smiled. They then reverse-engineered the data, and were surprised at the findings.

“We thought either the babies had no goal or it was about mutual smiling,” said Paul Ruvolo, a professor at Olin College of Engineering and an alumnus of the Jacobs School of Engineering at UC San Diego. “We are not claiming that a particular cognitive mechanism, for instance conscious deliberation, is responsible for the observed behaviors. Our methods are agnostic to this question.”

To confirm the preliminary findings, the researchers then employed the help of 32 San Diego undergraduates, to interact with "Diego San," a robot that was programmed to mimic four different behaviors of babies that were found during the previous study. The students behaved like the mothers, smiling while Diego San didn't smile as much.

Diego San got the students to smile as much as possible, while himself smiling as little as possible. This confirmed the first study's results, that babies do use timed smiles to elicit more smiles from people.

"Mothers consistently attempted to maximize the time spent in mutual smiling, while infants tried to maximize mother-only smile time," the study said, as per the San Diego Union Tribune.

“What makes our study unique is that previous approaches to studying infant-parent interaction essentially describe patterns,” said study co-author Dan Messinger, from the University of Miami.

“But we couldn’t say what the mother or infant is trying to obtain in the interaction. Here we find that infants have their own goals in the interaction, even before four months of age.”