苦痛と恐怖の動因弁別学習

抄録

Hull and Leeper questioned whether animals are capable of acquiring differential reactions based solely on internal cues and it was found that, while their rats took one path way to food when hungry, their rats were led to water when thirsty. And, Kendler contributed to the drive discrimination studies, with his experiments on the drive interaction.
Our interests are on the aversive aspect of motivation, such as pain, fear and anxiety. Our hypothesis is that, while rats can take one path way to non-shock side when pain is presented, rats can be led to non-buzzer side when fear is presented. Kendler found the drive interaction by the simultaneous presentation of two drives, but in our case, two drives of pain and fear were presented by rapid alternation.
Sixteen albino rats were used. The procedure for fear drive conditioning was given in a shuttle box with buzzer and shock pairing. And the procedure for drive discrimination was given in a T-discrimination box. The experimental design is shown on Table 1. Subgroup 1 and 2 were given additional fear conditioning in the starting point in the T-discrimination box for making difference on the fear drive level. Thirty trials were made in each session. Inter-trial interval was 30sec. The second session was reversal learning situation.
Table 2 shows the results of the drive discrimination by fear only and the ones by fear and pain drives occurred alternately. The table is a statistical analysis on order of occurrence of successive correct responses. Comparisons between pain and fear on error scores and running speeds are shown on Table 3 and 4. Pain discrimination is much superior to fear. On Fig. 4, the top curve shows error scores produced by fear drive which accompanies pain drive and the second one shows scores produced by fear only. This is interpreted as the drive interaction. Higher level of aversive motivation is worse in discrimination and gives more fixation effect to performance. The effect of the reversal learning gave influence only to the performance produced by weaker level of drive. Fig. 7 shows learning effects in fear discrimination training.
There are theoretical and experimental difficulties when we take the problem of drive discrimination by pain and fear, in comparison with the internal stumuli such as hunger and thirst. Pain and fear are considered as exteroceptive drive and always accompany the external stimulations. This experiment depends upon the conceptualization of the aversive motivation by Miller, Mowrer and Spence. Pain and fear occur very rapidly and impel response very strongly. Such rapidness and strongness are characteristics of the aversive motivation. And from an additional experiment, we found out two types of adaptable response, that is, the first type is the discrimination between pain and fear, and the second type is the discrimination between pain and pain-fear-chain responses. The problems mentioned above were discussed in the article.