The effect of electric shock on learning (II) -an analysis of the variously increased intensity of shock for correct responses in a black-white discrimination in the white rat-

Abstract

It has been shown by Muenzinger (6, 8) that moderate electric shock for correct selection after passing the point of choice has an accelerating effect upon the visual discrimination in a corrective and a non-corrective situation. Wischner's result (21), however, was different from Muenzinger's.
Considering that the difference of their results might be caused by their methodology, we designed in this experiment to examine the relationship between the intensity of electric shock and the task difficulty.
Subjects : 24 albino rats (males) were used.
Apparatus : A simple Y-typed maze provided with electrodes in both choice alleys (Fig. 1). The shocking device delivered ten direct correct impulses per second, which were of rectangular shape and whose amplitudes could be varied. The source of the D. C. shock administered to the Ss was a KX-5 Z 3 vacuum tube with a plate voltage of 650 v..
Procedure : In a non-corrective situation the animals of easy task (E. T.) group were trained in a black (negative) -white (positive) card discrimination, and the those of difficult task (D. T.) group in a 1/4 white (negative) -white (positive) card discrimination with 23 hr. hunger-food motivation. After exploration and pre-training for six days, all rats were divided into three groups, two experimental and one control. Experimental groups were consisted of medium shock (M. S. ; 30-100 μA.) group and high shock (H. S. ; 30-180 μA.) group (Table 1, 2).Each S was given five reinforcements per day and thereafter ten per day until 130 had been given. The intertrial interval was 45 sec.. The criterion of learning was two successive errorless daily sessions of ten reinforcements except initial one, and then it remained constant in each level.
Results : In terms of reinforcements, trials and wrong turns before reaching the criterion, each of E. T. group was significantly superior to its D. T. group, and each M. S. group and H. S. group was significantly superior to the N. S. group, but it was not significant between each M. S. and H. S. group (Table 3, 4).
These results support Muenzinger's suggestion that shock exerts a facilitating effect upon the learning. The new finding in present experiment were as follows : (1) A comparison of 30-100 vs. 30-180 μA shock group was not significant, and (2) the accelerating effect of shock was strongly manifest in earlier phase of learning process in a non-corrective situation (Fig. 2). Therefore, the authors assumed that Muenzinger's explanation was not enough to given an account of the facts shown in this experiment. It was also suggested that in a frustration situation there was an interaction between the process of cognitive differentiation and behavioral adjustment, and yet the facilitating effect of shock depended upon a harmonious interrelationship between both processes.