Most people agree that there’s something very special about a baby’s smile.  But is there a purpose behind that smile? What are they trying to communicate to us?

A new multidisciplinary study has found that babies smile to get you to interact with them and smile back.

Writing in the recent issue of the journal PLOS ONE, the researchers also found that much like successful comedians who go for the big laugh, babies have a great sense of timing that helps get adults to smile back, without having to smile too much themselves.

“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 study author Javier Movellan, from Machine Perception Laboratory at the University of California, San Diego in a university release.  “But proving this is difficult,” he added.

The research team, which included computer scientists, roboticists and developmental psychologists, took data gathered in a past study that examined the one-on-one interactions between mothers and their under-four-month-old children. Among the reactions taken from previous research included when and how often the mothers and their babies smiled.

With this data, the researchers programmed a child-like robot that could mimic the actions of the babies who were part of the earlier study. They then had the robots interact with student volunteers.

The scientists found that their experiment verified findings of the previous study.  The robot babies were able to provoke the same reactions from the students as the mothers who had been with their real-life babies. The baby bots, like their live counterparts, got the students to smile without having to smile much themselves.

Funded by the National Science Foundation, the study is part of a program that uses robots to get fresh insight into human development.

The research team is hoping that the program will provide developmental psychologists with new tools that will help them study children and adults who are unable to communicate verbally, such as those with autism.

Video of child-like robot used in study (Jacob School of Engineering @ University of California, San Diego