When a baby smiles, it is hard not to smile back. Now, with the help of a toddler-like robot, researchers from the University of California-San Diego have shed light on why: babies time their smiles in order to gain one in return.

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With the help of Diego-san – a toddler-like robot – researchers have uncovered the motive behind an infant’s irresistible smile.
Image credit: David Hanson/Machine Perception Laboratory

“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,” notes study co-author Javier Movellan, of the Machine Perception Laboratory at the University of California-San Diego (UCSD). “But proving this is difficult.”

In an attempt to do so, the team used data from previous research that looked at face-to-face interactions between 13 mothers and their infants, who were ages 4-17 weeks. The research gathered data on how often mother and baby smiled at each other and exactly when they smiled.

Applying reverse-control theory algorithms to the results, the researchers found that 11 of the 13 babies adopted “sophisticated timing” of their smiles in order to gain a smile from their mother; mothers were most likely to smile when their baby’s smiling was minimal.

“That is, infants had the goal of creating and maintaining states in which they were being smiled at (by their mothers) but were not smiling themselves,” explain the researchers.

The researchers set out to validate these findings with the help of 32 UCSD undergraduates and a toddler-like robot named Diego-san.

Each student acted as the robot’s caregiver in 3-minute sessions, and the robot was programmed to display one of four behaviors often adopted by 1-year-old babies. These behaviors were dependent on the facial expressions of the student.

The video below shows Diego-san in action:

Confirming the results of the previous analysis of the 13 mother-baby pairs, the researchers found that the students smiled once the robot’s smiling ceased, supporting the idea that babies time their smiles as a way of gaining one in return.

Commenting on their findings, published in the journal PLOS ONE, the researchers say:

We found that infant (and mother) timed their smiles in a sophisticated manner that demonstrated mastery of the statistics of social interaction. Both partners timed their smiling to have a systematic impact on the other partner. We do not claim, however, that either partner was aware of timing their smiles in order to achieve a specific goal.

These results nevertheless suggest that infants leveraged social interaction patterns to achieve specific dyadic states well before there is evidence for conventional use of means-to-ends behavior.”

While the team says these findings shed light on mother-baby interaction, they believe the approach used in this study could also increase understanding of typical and atypical social behavior among infants.

For example, they say it could be used to analyze the interactive behavior of children at high risk of autism spectrum disorder (ASD). “The analysis could help disambiguate whether young infants who will go on to develop an ASD have more object-oriented and less socially-oriented goals than infants who do not go on to an ASD outcome,” they add.

It seems robotics are being increasingly incorporated in the medical field. Earlier this year, Medical News Today reported on a study detailing the creation of “soft micro-robots” that researchers say could one day perform biopsies or deliver drugs.