Cats, who had displayed escape or “fear”-like behavior by electrical stimulation of the midbrain central gray, were trained to interrupt the delivery of electrical stimulation of the midbrain central gray by plate pushing (switch-off behavior). After cats successfully learned to perform this switch-off behavior, they were further subjected avoidance conditioning trials in which neutral stimulus such as bell sound served as conditioned stimulus (CS), and electrical midbrain central gray stimulation as unconditioned stimulus (UCS). After cats reached the criterion of the avoidance learning, that is, appearance of the conditioned avoidance responses (CR) above 80%, then they were subjected extinction trials until they showed no CR. After that, they were given re-conditioning trials and extinction trials.
Results are following :
1. Four cats out of seven succeeded in avoidance learning. Their stimulation sites were in the mid-paramedian position of the periaquedual gray matter (see Figs. 1 and 2).
2. Two cats showed CR a little. One cat completely failed to show CR. Their stimulation points were in the basic and medial position of the midbrain central gray (see Figs. 1, 3, 4 and 5).
These findings suggest differences between learning induced by intracranial stimulation and that induced by peripheral stimulation, and also differences between avoidance learning based on switch-off behavior induced by midbrain stimulation and that induced by hypothalamic stimulation.

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To compare the extinction effect of latent extinction or non-response extinction, and response extinction, two experiments using a SALZMAN-type U-maze were performed.
In Experiment I, the effect of latent extinction did not differ significantly from that of response extinction by free choice (Fig. 2, Table 2). Contradicting DEESE'S (1) results, a tendency to spontaneous recovery from latent extinction was found. A significant latent extinction was also found.
In Experiment II, response extinction by forced choice produced significantly greater extinction than latent extinction and that tendency did not disappear even after overtraining in 50 trials (Fig. 3, Table 5).
Summarizing the two experiments together with DEESE'S (1) results, it is concluded that a latent extinction effect can be induced in a U-maze, but it is inferior to a response extinction effect.

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The social facilitation phenomena of feeding behavior observed experimentally in each group of fish, Rhodeus, Acheilognathus and Rhinogobius, are reported here. The following results were obtained :
1). As was clearly shown in the experiment on the social facilitation phenomenon of feeding behavior in young fish of Rhodeus, the significant difference among 1, 2- and 4-grouped fish on the feeding rate per 100mg body weight of fish were observed.
2). It was found that the phenomenon concerned is occurred probably by adult of Acheilognathus, too.
3). Although, facilitation rate lower than in guppy, the phenomenon was also observed in group of young adult Rhinogobius.
4). While, in the case of four or more number of individuals of the stimulators, the feeding amount in the reacting fish, Rhinogobius, came to maximum and constant value.
5). Importance on a process of social facilitation depended upon 'the presence recognition effect' was pointed out by these experiments.

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The purpose of the present experiment was to study the effects of delay of intracranial reinforcement upon a simple Y-maze discrimination learning and to consider if secondary reinforcement is so established by central stimulation as food e. g. PERKINS (1947) and WOLFE (1934).
17 rats with a chronically implanted bipolar electrode that had learned enough to press a bar for lateral hypothalamic electrical stimulation in Skinner box were preliminary trained to run a straight alley. On the test trials, individual Ss were randomly assigned to the four different delay groups. Delay of 0, 5, 15, and 45 sec. were employed. All Ss in this period received ten massed runs a day for 8 successive days, respectably with each delay of optimal intracranial reward. After all series had been completed, Ss were sacrificed and electrode loci determined.
Results from four groups were as follows :
1. Three groups with delays of reward 0, 5, and 15 sec. tended to show a correct choice in 60 trials, while the group with 45 sec. delay did not show the satisfactory learning curve. Therefore it was suggested that delay of reinforcement gradient is even in a situation of intracranial reinforcement.
2. The slope of the gradient obtained in the present experiment was not so steep as reported by KEESEY (1964) that set up more less external and internal stimuli during the delay period. This difference of the gradients corresponded with that between GRICE (1948) and PERKINS (1947) or WOLFE (1934).
3. Especially, the fact that learning was established even in delays of 5 and 15 sec. in this experiment suggests that the secondary reinforcing agent acted upon learning for intracranial stimulation. However, the value of the secondary reinforcement was possibly poorer than in peripheral stimulating situation.

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[in Japanese]

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