A Comparison of Two Discrimination Procedures in Avoidance Conditioning in the White Rat.

Abstract

It is theoretically inferred that the discrimination in avoidance conditioning is difficult in typical discrimination procedure when two stimuli to be discriminated are very similar. PAVLOV and LAWRENCE have reported that a difficult discrimination between two quite similar stimuli is more efficient when subjects are first trained on an easy discrimination between two dissimilar stimuli and then gradually approach the difficult one than if all the training is given directly on the difficult discrimination. The purpose of this experiment is to compare the efficiency of these two procedures on discrimination in avoidance conditioning.Method Subjects : The Ss were 49 male albino rats. Apparatus : The apparatus was the modified MOWRER-MILLER shuttlebox. Procedure : After the establishment of avoidance conditioning to the CS which was 2000 cps tone, dicrimination training started. Hard Discrimination Group-I (HDG-I) was trained on the discrimination between 2000 cps (S+) and 1500 cps tone (S-) throughout 15 days. Hard Discrimination Group-II (HDG-II) was given the same procedure as HDG-I, but training was continued for 25 days. Gradual Transition Group-I (GTG-I) started on the discrimination between 2000 cps and 500 cps tone (S-) and then the S- gradually approached the 1500 cps tone through a series of graduated steps. The S- rose to 1500 cps by giving 250 cps every three days. Gradual Transition Group-II (GTG-II) was giving the same procedure as GTG-I, but the S- rose every five days (See Table 1).Results 1). The discrimination curves for each group are shown in Fig. 1 and 2. There was statistically significant difference between the number of responses to the S+ and S- at the last step of discrimination training for each group. This means that discrimination between S+and S- was established for each group. 2). In order to make comparisons between groups, discrimination ratios (S+-S-/S+) were calculated as an indicator of discrimination learning. Curves of them in the last training step for four groups are presented in Fig. 3. As a result of statistical comparisons between groups on these ratios, no significant difference was shown between HDG-I and GTG-I, but between HDG-II and GTG-II. This suggests that the difficult discrimination between two very similar stimuli in avoidance conditioning was more efficient when subjects approached the difficult discrimination through a series of graduated steps than if all the training was given directly on the difficult one. This also suggests that one of the important factors for this effect was the duration of a step, that is to say, this effect was not obtained in case of the short duration of a step.