Effects on Performance of Interpolated Tasks During the KR Delay or the Post-KR Delay Interval

The present study was designed to investigate the nature of motor information processing in the intertrial intervals of a discrete motor task. In Experiment 1, the subjects were given the task of grasping the dynamometer with an intensity yielding a value as close as possible to the target value (40% of the subject's maximum grasping power). The exercise session consisted of 5 trials without Knowledge of Results (NO-KR phase), and 30 trials with Knowledge of Results (KR phase). In the KR phase, one of the two interpolated tasks, one was a verbal task and the other was a motor task, was given during the KR delay interval or the post-KR delay interval. Performance level in the exercise session was measured by constant error and variable error. In Experiment 2, the degrees of difficulty in the two types of interpolated tasks used in Experiment 1 were measured. The main results of our experiments were as follows; (1) Although the results of Experiment 2 showed that the difficulty of the verbal interpolated task was exceeded that of the motor interpolated task, only variable errors of the groups which had executed the motor interpolated task were increased. If the kinetic sense was changed by executing the motor interpolated task, constant error should have increased. The results of Experiment 1, however, showed no difference in constant error, suggesting that the occurrence of interference by the motor interpolated task is related to the capacity of the motor short term memory space. (2) In the latter period of the KR phase, variable error of the group in which the motor task was interpolated during the KR delay interval was at the same level as that of the control group. Whereas variable error of the group in which the motor task was interpolated during the post-KR delay interval exceeded that of the control group over the whole of the KR phase. These results suggest information processing during the post-KR delay interval has more influence on performance than that during the KR delay interval.