Analysis of motor disorder in retarded infants and young children.

A prospective longitudinal study of 53 retarded infants and young children without evidence of a frank physical disability suggests that their delayed motor development was related to a subtle but specific disturbance in the evolution of infantile reflex behavior. The aberration was characterized by a delay in the appearance of postural adjustment reactions, specifically, of propping and equilibrium responses that, under normal circumstances, precede the accomplishment of successive gross-motor milestones. Motor development in this selected group of retarded children was delayed for their chronological age but was consistent with the maturational level of postural adjustment reactions.