恐怖動因と補強価の転換性

Abstract

According to N. E. Miller, fear is a learnable drive, and therefore, is defined as response-produced stimulus. Confronting danger situation, animal responds to it with the muscle tension and this tense response becomes stimulus in the organism which works as a drive or cue for further instrumental response.Ordinarily drive state is controled on a certain level (e.g. 23hrs. hunger drive), and cue is given a certain distinctiveness. There is established a univocal relationship between them. However the drive state has oscillation in itself. A response produces oscillation in a drive state and the varied drive state produces further instrumental responses. We postulate that the reinforcing value which the stimulus context carries, is reversible from rewarding to punishing, and vice versa, in accordance with the variability of the drive state that occurs with the lapse of time.Experiment I. In order to test the hypothesis of the reversibleness of reinforcing value in the stimulus context, three kinds of stimulus contexts, that is, buzzer-shock (black wall): buzzer-shock (white), buzzer-shock (black): shock (white), shock (black): shock (white) were used in a shuttle box. Number of avoidance responses is shown in Table 1. When animal runs to white side, the white side is rewarding, but this side becomes gradually punishing as time goes by, then he returns to the black side.Experiment II. In order to find the effect of the variability of the drive state which occurs with the lapse of time, animal was trained on avoidance in buzzer-shock: shock, or the unequal reinforcingstimulus context. The results are shown in the Tables 2, 3, 4. On the first day of training, animal stayed for 19.22min. out of 40.00min. on the black side, and on the last day of training, they stayed for 28.51min.. Animal may be said to prefer to stay more on the fear-reducing side than on the tense side. This is supported by the relative reinforcement theory of C. C. Perkins, Jr., though his theory does not necessarily require the drive concept.Experiment III. Fear works adaptably to any abrupt change of the stimulus context. After the completion of the avoidance training in buzzershock: shock stimuluss context, an extinction trial was introduced. The original black wall was suddenly replaced by an inserted white wall, and the original white by the inserted black one. The original and inserted stimuli were alternately presented for one min. each, and duration of stay on both sides was measured. As Fig. 1 shows, animal responds to the inserted black side with an adaptable avoidance. The curve for the duration of stay on the black side goes up until no difference is seen between the 9th inserted trial and the 10th original trial. In addition to this, a striped wall was used as an inserted wall. Almost the same result is shown in Fig. 2.