It is a general tendency that a partial reinforcement effect (PRE) is not found in the fish. However, there are some evidences that nonreinforcement influenced learning and extinction process. The present experiment, was conducted to investigate the effects of nonreinforcement on resistance to extinction of the fish under high reward magnitude. In addition, the effect of overtraining on extinction was investigated.
24 goldfish were trained and extinguished with massed trials in the alley-type apparatus. In the E group, 24 successive nonreward trials were interpolated into the total of 69 acquisition trials (consequently, the E received 65% partial reinforcement). The C group received 100% continuous reinforcement (see the under part of Fig. 1).
The E was less resistant than the C, and PRE was not obtained in terms of between-groups (Fig. 1) and of within-group (Fig. 2 (A)). Overtraining did not facilitate the extinction of the C group (Fig. 2 (B)). These results indicate that resistance to extinction depends on the habit strength which increased as a function of number of reward trials, and suggest that the aftereffect of nonreinforcement has not a positive effect to control the behavior of fish.

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The purpose of this study is to investigate temporal discrimination in pigeons using a modified differential reinforcement of long latencies (DRLL) schedule. A sample duration, which was equal to a specified minimum reinforced latency (t), was presented before each trial. Moreover, a limited hold contingency was added to the schedule. The length of the limited hold was equal to t. Therefore, a response whose latency was between t and 2t sec produced reinforcement.
Pigeons were trained under several values of t (Table 1). The results of the training period were as follows :
1) Latency distributions were unimodal ones having their peaks near t (Fig. 1).
2) Mean latency was well described as a power function of t. The values of the exponent of the power function obtained were slightly less than 1.0 (Fig. 2).
3) Coefficients of variation were fairly constant over all values of t (Fig. 3).
After the training, test sessions were carried out in order to examine whether or not the sample duration exerted control over the latency. In these sessions, response latencies for the seven different sample durations were obtained under extinction situation. The results revealed that the sample duration did not acquire discriminative control over the spaced responding (Fig. 4).

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[in Japanese]

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[in Japanese]

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The response-duration schedule in which rat receives a food pellet after releasing the bar providing that barpress duration exceeds the prerequisite time-interval has been scarcely investigated in its own right (1, 2, 5, 6). The purpose of this experiment was to obtain some elementary data about the properties of brief barpress and the effect of synchronized presentation of a cue light with each bar-holding upon the relative frequency of brief barpress.
Ss were 17 albino rats. Three conditioning chambers with ordinary rodent lever were controlled by a microcomputer system. Exteroceptive stimulus was a cue light presented above each lever. After pretraining, each Ss was trained to press a bar under the response-duration schedule of 0.8 sec. (phase 1) and then 1.6 sec. (phase 2, 3) with or without cue stimulus (See Table 1 and Fig. 1). Asymptotic level of relative frequency of reinforced responses and median responseduration in phase 3 showed no marked improvement in condition S-2 and S-3.On the other hand, the analysis of covariance for relative frequency of brief (0.2 sec.) barpresses with relative frequency of reinforced responses showed significant difference between condition S-0 and S-1 in phase 2. In other words, the feedback cue light tended to decrease the relative frequency of brief barpress. Close inspection of temporal allocation of brief barpresses indicated that most of them were occured closely to the preceding or following barpresses (Table 3).

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