Investigations of the differences in movement speed over the age span, childhood to early adulthood, have typically confounded age with size differences which bring about mechanical differences in the task. The present study investigated the effect on arm movement time of confounding age and limb length. Young adults and children 7 to 9 yr. of age were tested over a distance proportional to their arm length. Despite moving over a proportionally shorter distance, the children were significantly slower than the adults, suggesting that age differences in performance are not solely attributable to size differences among subjects.
