Rock with me: the role of movement synchrony in infants' social and nonsocial choices.

Matching the timing of one's movements to the movements of others has been proposed to increase affiliation and prosociality. Although coordinated movements facilitate early social interactions, not much is known about the mechanisms and effects of movement synchrony throughout development. Two studies investigated 12-month-olds' (Study 1, N = 40) and 9-month-olds' (Study 2, N = 41) preferences for synchronous others in a social as opposed to a nonsocial context. It was found that movement synchrony exclusively guides infants' social choices at 12 months. In contrast, 9-month-olds did not show any preferences for synchronous movements in social or nonsocial contexts. Results suggest that movement synchrony is important in guiding infants' social preferences and its effects emerge toward the end of the 1st year of life.