A new study has found that babies as young as four months old do not simply smile at random. They carefully time their grins to get the biggest smile in return from their mothers.

Researchers from the University of California San Diego, Olin College in Massachusetts, and the University of Miami observed 13 mother-infant pairs, using advanced computational methods to analyse their face-to-face interactions.

The findings revealed that 11 of the babies used a clever strategy, making their mothers smile as much as possible while limiting their own smiling.

This approach is not unlike that of a seasoned comedian who gauges exactly when to draw a reaction from an audience. To put their theory to the test, the scientists programmed a toddler-like robot, Diego-san, to use the same smile-timing tactics.

When interacting with 32 university students, the robot managed to draw frequent smiles from the group without needing to smile itself nearly as often, mirroring the babies’ social success.

The research challenges the notion that babies’ earliest smiles are purely reflexive. Instead, it suggests that even at a few months old, infants are learning to achieve social goals through nuanced behaviour.

These insights not only shed light on early parent-child bonding but could also help inform the future design of social robots and deepen our understanding of developmental disorders such as autism.