Thirteen mothers with their four-month-old children participated in the experiment, as well as volunteers who interacted with robotic dolls, very similar to babies. The task of the scientists was to understand why the children smile: they do it just like that? Or take into account those or other circumstances?
The results were largely unexpected. Firstly, it turned out that infants in the field of relations with their parents are not cute fools, but trained specialists. They behave the same way as professional comedians, who understand at what point the audience is most prepared for the perception of a joke. Specifically, the child smiles to the mother or father just when the parents are smiling to respond and, moreover, when they are set to smile as long as possible. These little "experts" in their four months already know exactly at what moment and how to look at their parents to attract the most of their attention.
But that is not all. Studies have shown that babies smile to their parents for a reason, not out of love for smiles and the process of "rejoice," but for parents to smile at. It turned out that babies and their mothers have different strategies. If the strategy of mothers was "let there be more time of our mutual with the child smiles," then the strategy of babies is much more focused: "let there be a greater time when my parents smile." Itself to smile just like that - no, children do not put such a task ... They have a goal: parents smiles, and they are achieving exactly this!
Infants Time Smiles to Make Their Moms Smile
One of the earliest forms of interaction between mothers and infants is smiling games. While the temporal dynamics of these games have been extensively studied, they are still not well understood. Why do the mothers and infants time their smiles the way they do? To answer this question we applied methods from control theory, an approach frequently used in robotics, to analyze and synthesize goal-oriented behavior. The results of our analysis show that by the time infants reach 4 months of age both mothers and infants time their smiles in a purposeful, goal-oriented manner. In our study, the mothers consistently attempted to maximize the time spent in mutual smiling, while the infants were trying to maximize the mother-only smile time. To validate this finding, we ported the smile timing strategy used by infants to a sophisticated child-like robot that automatically perceived and produced smiles while interacting with adults. As predicted, this strategy proved successful at maximizing the adult-only smile time. The results indicate that by 4 months of age infants interact with their mothers in a goal-oriented manner, utilizing a sophisticated understanding of timing in social interactions. Our work suggests that control theory is a promising technique for both analyzing complex behavior and providing new insights into the development of social communication.