Developmental correspondence between action prediction and motor ability in early infancy.

How do infants understand the goals of others' actions? It has been proposed that action-understanding results from a mechanism whereby an observed action is mapped onto the observer's own motor representation of that action. However, direct evidence of the matching process in early infancy is difficult to find. Here we show the developmental correspondence between action prediction and motor ability by comparing gazing and grasping responses to interesting objects in 4- to 10-month-old infants and adults. The onset of infants' ability to predict the goal of others' action was found to be synchronized with the onset of their own ability to perform that action. Moreover, there was correspondence relationship between action-prediction ability and motor ability of same action. Our findings indicate that the ability to predict others' action goals requires a corresponding motor ability, providing ontogenetic evidence for a direct matching process by a mirror neuron system.