Visual discrimination and motor reproduction of movement by individuals with mental retardation.

Visual discrimination and motor reproduction tasks involving computer-simulated arm movements were administered to 12 adults with mental retardation and a gender-matched control group to examine whether inadequacies in visual perception account for the poorer motor performance of individuals with mental retardation. In the discrimination phase subjects judged whether simulated arm movements were either of greater or lesser extent or shorter or longer in duration, respectively, than those of a standard display. In the reproduction phase accuracy in reproducing the movement in the standard display was measured. Results indicate that error in discriminating extent and duration was significantly greater for the individuals with mental retardation, who were also less accurate and more variable in matching the extent and duration of the standard displays. These outcomes implicate both perceptual and motor-reproduction inadequacies in skill acquisition for these individuals.