Infants' use of movement synchrony to infer social affiliation in others.

Infants socially engage with others and observe others' social interactions from early in life. One characteristic found to be important for signaling and establishing affiliative social relationships is physical coordination and synchronization of movements. This study investigated whether synchrony in others' movements signals affiliation to 12- and 15-month-old infants. The infants were shown a scene in which two characters moved either synchronously or non-synchronously with a third character in the center. Next, the center character made an affiliation declaration and subsequently approached and cuddled one of the two characters. Using measures of gaze, we gauged infants' inferences about whom the center character would affiliate with before the cuddling took place. We found that 15-month-olds, but not 12-month-olds, inferred that the center character would affiliate with the previously synchronous character, suggesting that they can make inferences about others' affiliation based on movement synchrony. The findings are discussed in terms of their relevance to the infants' personal preferences and the potential importance of first-person experience in the development of social cognition.