On conditioned inhibition in human motor learning

Abstract

The present investigation was designed to test the existence of a conditioned inhibition, sIr, which has been postulated by Hull, Kimble and others, on the basis of a critique already reported by the writer.
The significant difference between pre-rest massed- and spaced practice groups in initial post-rest performance has been considered as the index of sIr by Hull and other, but this phenomenon may rather be interpreted by the difference in the level of skill acquired during pre-rest practice. Then, in accordance with this critique, I propose that, after the same number of trials in pre-rest practice on a poor-skilled task, the level of skill for the massed group would differ from that for the spaced group. Consequently, the difference in performalce between the two groups may be seen after an interpolated rest. But I propose that for a well-skilled. task, the difference in performance between-the, two groups seen in the pre-rest practice would not be observed in the post-rest performance, as the level of skill has already reached the asymptote. But if the difference is observed in the post-rest. performance in the latter task, it may be a prominent evidence for sIr.
The present investigation consists of three experiments, each containing two tasks, a poor-skilled, task (correct-copying inverted Japanese Hirakana letters in each compartment provided, e. g., _??_) and a well-skilled task (_??_-check or ⊕ task-writing the circles and cross or × in it).
In the procedure of Exp. 1., all Ss received 20-30 sec. trials which massed group of 40 Ss received without rest, and which spaced group of 40 Ss received with 30 sec. intertrial rest. Following 10 min. rest interpolated between pre- and post-rest practices, all Ss received 15 trials without rest.
In Exp. 2., based on the reflexion that appreciable sIr may not develop at a short practice, and to supplement for such possibility, all Ss received 80 30-sec. trials which 20 Ss received without rest, and which other 20 Ss received with intertrial 30 sec. rest. Following 10 min. rest, all Ss receieved 10 massed trials.
In Exp. 3., in order to eliminate the influence of fatigue, all Ss practiced 4 sessions separated by rest for 24 hrs., each session being constituted of 20 trials, with massed or spaced conditions (50 Ss in massed group, 45 Ss in spaced group on Hirakana correct-copy task, and 40 Ss in each group of ⊕ task). After 10 min. rest interpolated following the fourth session, all Ss received 1O massed-trials.
The obtained results in Exp. 1. and 2. showed that spaced group was significantly superior to massed group during pre-rest practice in both tasks, but as regards post-resti performance, the significant difference between the two groups obtained on Hirakana correct-copy task was not obtained on ⊕ task.
The result in Exp. 3. showed that the difference between the two groups obtained at the first trial in each practice-session on Hirakana correct-copy task increased in a straight slope, but the significant difference between the two groups was not observed on ⊕ task. In addition, the significant difference between the two groups obtained in test performance on Hirakana correct-copy task was not observed on ⊕ task.
From the above-mentioned experimental results, the difference between massed- and spaced groups obtained on Hirakana correct-copy task over all experiments may be interpreted with different levels of skill acquired by each group during pre-rest practice, rather than as evidence for the existence of sIr. This proposition may be confirmed by comparison with ⊕ task and from the results of other investigators. Thus, we may conclude with Underwood, Ammons and others that sIr is probably an unnecessary construct.