THE EFFECTS OF PRACTICE ON MOVEMENT REPRODUCTION - IMPLICATIONS FOR MODELS OF MOTOR CONTROL

This study investigated how consistently and accurately subjects could reproduce final movement position when performing three different mov ement tasks over four experimental sessions. Task 1 involved moving fi ve different inertial loads over one movement distance. Task involved performing movements over five different distances against a constant inertial load. Task 3 involved moving five distances against five iner tial loads that were adjusted to keep movement time relatively constan t. Subjects who had practised Task 1 demonstrated the largest decrease in variable error over experimental sessions but little change in con stant error. Subjects who had practised Task 2 showed a smaller improv ement in variable error and no improvement in constant error. Subjects who had practised Task 3 demonstrated a small change in variable erro r and an improvement in constant error. The largest reduction in varia ble error in the first group is consistent with the equilibrium-point hypothesis of motor control but not with force-control models. The imp rovement in constant error in the third group is discussed with respec t to a possible role of noise in practising simple movements.