Study: Why Babies Smile (VIDEO)

First Posted: Sep 24, 2015 12:38 PM EDT

A team of researchers out of the University of California-San Diego have discovered that there is a hidden agenda behind a baby's smile...they want to make their mothers smile, too.

Babies are basically like comedians, using sophisticated timing to maximize the response of their audience, which is in this case, their mothers.

The study, which details an innovative method of discovery, had researchers using a combination of developmental psychology, computer science, and robotics. As far as the researchers know, this approach has never been taken before, according to the release.

"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," Javier Movellan, a study author and research scientist in the Machine Perception Laboratory at the University of California, said. "But proving this is difficult."

The team took data from a previous study that observed face-to-face interactions of 13 pairs of mothers and under-four-month babies, which included when and how often both mother and child smiled, and ran the data through their reverse-control theory algorithms.

They then programmed a toddler-like robot to behave like the babies they studied, and had it interact with undergraduate students, and were surprised at their findings.

"We thought either the babies had no goal or it was about mutual smiling," Paul Ruvolo, a professor at Olin College of Engineering, said. "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."

Researchers were very cautious in pointing out that they can't completely determine if the babies are conscious of their actions, as it is very difficult to prove.

In order to figure out what babies are up to when they smile, the team used optimal control theory, a tool used regularly in robotics. The allows them to reverse engineer what the babies' goals were, based on their behavior.

Despite the small sample size, the findings were statistically strong, according to Movellan. Their analysis found that 11 out of the 13 babies in the study showed clear signs of intentional smiling.

"Our goal was to have human development inform the development of social robots," said Ruvolo. Movellan confirmed that the team took several years to develop a realistic robot.

"What makes our study unique is that previous approaches to studying infant-parent interaction essentially describe patterns," said co-author Dan Messinger, of 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."

The study was a part of the National Science Foundation's effort to use robots to better understand human development, allowing researchers to have a tool to study non-verbal children and adults, as well as those with autism.

(video courtesy of the University of California-San Diego)