ERPs reveal perceptual and conceptual processing in 14-month-olds' observation of complete and incomplete action end-states.

Infants in the second year of life not only detect the visible goals or end-states of other people's action, but they also seem to be able to infer others' underlying intentions. The present study used event-related potentials (ERPs) to investigate the biological basis of infants' processing of others' goal-directed actions, with special regard to the involvement of bottom-up perceptual and top-down conceptual processes. In an adaptation of the behavioral re-enactment procedure, 14-month-olds were first familiarized with either full demonstrations (FD), failed attempts (FA), or arbitrary (AA) object-directed actions. Next, ERPs were measured while all infants saw the same two pictures of the end-states of the full demonstration (complete end-state) and the failed attempt (incomplete end-state). In the time-windows related to perceptual processing (100-200ms after stimulus onset) and to conceptual processing (300-700ms), ERP negativity over frontal and central regions was higher for the complete than for the incomplete end-state in the FD and FA conditions. When comparing the FA and AA conditions, this pattern of results occurred only for the conceptual time domain. Moreover, beginning slow-wave activity (700-1000ms) differed for the end-state pictures in the three conditions, suggesting differential encoding demands. Together, the electrophysiological data indicate that infants in the second year of life use bottom-up perceptual as well as top-down conceptual processing to give meaning to others' goal-directed actions.