Exploring 12-Month-Old Infants' Processing of Other People's Manual Actions: A Motor Interference Paradigm

Inferring the goals of other people's actions is an important aspect of early social cognitive development. Using an experimental manipulation, we investigated the role of infant motor processes in the processing of action they see performed by another person. We designed a procedure in which we inhibited infants' concurrent access to motor representations of precision grasping as they observed the reach-to-grasp action of an adult experimenter. In a within-subjects design, 48 12-month-olds watched adult reach-to-grasp actions under two conditions of hand posture in randomly-assigned order: (a) hands free and (b) hands constrained in a manner that blocked their grip formation. Infant looking times were measured as an experimenter reached toward large and small objects, using a power or precision grip type. Infants' prior-existing fine motor skills were assessed using a standardized parental report questionnaire. Results showed that infant looking times varied as a function of the interaction between infants' existing fine motor skill and their experimentally-manipulated access to motor representations of the action (p = 0.017). The better an infant's fine motor skills, the greater the reduction in their looking to the object congruent with the actor's grip type under the motor interference induced by hand constraint. This effect was particularly pronounced during the precision grip trials (p = 0.032). These findings advance our understanding of the role that infants' self-experience plays in the processing of the manual actions of others. More generally, such results inform theories about the functional significance of action perception-production links in early human development.