Interpersonal synchrony increases prosocial behavior in infants

July 1, 2014 11:42 am

Moving with a partner to the musical beat may make people more cooperative — even babies as young as 14 months.
Researchers worked with 48 toddlers, each held by an assistant and gently bounced for about two minutes to the rhythm of the Beatles’ version of “Twist and Shout.” They faced an experimenter who bounced in the same rhythm or off the beat.

Then the scientists tested whether the babies would help out when an experimenter “accidentally” dropped an object, or tried to pick up an object just out of hand’s reach. The study was published online in Developmental Science.

After controlling for other behaviors, such as smiling or approaching the experimenter, they found that babies who were bounced in a synchronous rhythm were slightly but significantly more likely to help than those who were bounced off beat. Although the effect was moderate, the authors say, it was still impressive given the quite short duration of the interaction.

“We tend to think that music is a frill that doesn’t matter,” said the lead author, Laurel J. Trainor, a professor of psychology at McMaster University in Hamilton, Ontario. “But in fact, these social binds that we form early in development affect everything that happens later, including our ability to learn and how we view others and ourselves.”


Adults who move together to a shared musical beat synchronously as opposed to asynchronously are subsequently more likely to display prosocial behaviors toward each other. The development of musical behaviors during infancy has been described previously, but the social implications of such behaviors in infancy have been little studied. In Experiment 1, each of 48 14-month-old infants was held by an assistant and gently bounced to music while facing the experimenter, who bounced either in-synchrony or out-of-synchrony with the way the infant was bounced.

The infants were then placed in a situation in which they had the opportunity to help the experimenter by handing objects to her that she had ‘accidently’ dropped. We found that 14-month-old infants were more likely to engage in altruistic behavior and help the experimenter after having been bounced to music in synchrony with her, compared to infants who were bounced to music asynchronously with her.

The results of Experiment 2, using anti-phase bouncing, suggest that this is due to the contingency of the synchronous movements as opposed to movement symmetry. These findings support the hypothesis that interpersonal motor synchrony might be one key component of musical engagement that encourages social bonds among group members, and suggest that this motor synchrony to music may promote the very early development of altruistic behavior.