Interindividual differences in neonatal imitation and the development of action chains in rhesus macaques.

The capacity to imitate facial gestures is highly variable in rhesus macaques and this variability may be related to differences in specific neurobehavioral patterns of development. This study evaluated the differential neonatal imitative response of 41 macaques in relation to the development of sensory, motor, and cognitive skills throughout the 1st month of life. The results show that infants who imitate facial gestures display more developed skills in goal-directed movements (reaching-grasping and fine hand motor control) than nonimitators. These differences might reflect, at least in part, the differential maturation of motor chains in the parietal and motor cortices, which partly overlap with those of the mirror neuron system. Thus, neonatal imitation appears to be a predictor of future neurobehavioral development.