The Effect of Practice on the Control of Sequential and Simultaneous Actions

The effect of practice on the control of sequential and simultaneous multilimb aiming responses was studied. In one group (n = l0), subjects pushed hand levers and foot pedals 20 deg. (plus or minus 1.5 deg.) forward in the following order: left hand, right hand, left foot, right foot. In the other group (n = l0), all subjects pushed both levers and pedals forward simultaneously for the same distance. The goal for both groups was to reduce movement time (MT). Analysis of the displacement and velocity records showed that sequential movements were made quicker and with fewer movement corrections than simultaneous movements. With practice, both groups reduced the MT and the number of movement corrections, suggesting that the accuracy of the initial propulsive phase of the movement became more precise. In addition, temporal interlimb correlations increased with practice, suggesting the development of a coordination factor related to multilimb movements, but little support was shown for the gear-shift analogy.