Fitts' reciprocal tapping task, a measure of motor capacity?

Employing Fitts' reciprocal tapping task, the capacity of the motor system in bits processed/second was assessed across different ages. In Exp. I a comparison was made among Grades 1, 5, 9, and university females. Motor capacity and average movement time/tap were significantly lower for Grade 1 girls than the other three grades. In addition, within-subject variability and percentage error rate decreased with increasing grade level. These findings were discussed in comparison to other studies looking at motor capacity changes across ages. Exp. II was designed to study the changes in motor capacity throughout 25 days of practice by two 5-yr.-old children. Two different methods were used to calculate motor capacity. One method (Kay, 1962) which assessed motor capacity separately for each tapping condition led to the conclusion that capacity increased with practice. A second method (Fitts & Peterson, 1964) treating all tapping conditions together in a regression equation and measuring capacity as the reciprocal of the slope (1/b) showed capacity to decrease with practice for one subject and oscillate with practice for the other subject. The general conclusion drawn from the two experiments was that motor capacity, as assessed by Fitts' tapping task, is not an extremely useful measure. Consideration of movement time is usually just as informative.