The effect of biomechanical properties of motion on infants' perception of goal-directed grasping actions.

From a very young age, infants perceive others' actions as goal directed. Yet, the processes underlying this competence are still debated. In this study, we investigated whether (a) 4- and 6-month-old infants and adults discriminate the biomechanical properties of the human hand within an action context, (b) the manipulation of the biomechanics of hand movements has an impact on the ability to anticipate the goal of an action, and (c) the emergence of motor experience with grasping is related to infants' ability to discriminate the biomechanics of hand movements and to anticipate the action goal. The 6-month-olds discriminated between biomechanically possible and impossible grasps, and in some (but not all) instances they made more anticipatory gaze shifts toward the goal of the possible action. Both the 4- and 6-month-olds' processing of biomechanical properties of the hand were significantly related to their ability to anticipate the goal of a grasping action. Importantly, those 4-month-olds with higher precision grasping skills manifested faster anticipatory gazes toward the goal of the action. These findings suggest that multiple sources of information from an action scene are interdependent and that both perceptual information and motor experience with an action are relevant for on-line prediction of the final goal of the action.