In order to evaluate the effect of continued rewarding trials on the discrimination reversal, 5 groups of albino rats (N=8) learned position discrimination in an alley Y-maze. Four overtraining groups received differential treatments in the period of overtraining. 100 : 0 group was forced to the correct side over 100 trials, and the other three (groups 100 : 50, 100 : 100 and 100 : 200) were forced to the correct side for 100 trials and to the incorrect for 50, 100 and 200 trials, respectively.
The effect of reversal facilitation was not obtained, and the reversal emerged to be retarded in groups 100 : 50, 100 : 100 and 100 : 200. And, the extinction of prior correct response was especially prolonged in 100 : 50 group.
Non-rewarding trials of incorrect response by means of forced choice method turned out to increase the inhibition of incorrect side beyond the degree in the original learning. Because of this complicating effectiveness of forced non-rewarding trials, the initial attempt was not accomplished.

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Massed extinction and spaced extinction were compared by a “distance maze” (Fig. 1) similar to the apparatus used by CRUTCHFIELD (4) and SOLOMON (11). The problem is to investigate the co-relation between inhibition and increased drive by non-reinforcement.
Subjects : Twenty-one white rats, five females and six males in one group (massed extinction) and five females and five males in other group (spaced extinction), about five months of age and 188. 1 g of mean weight were used.
Apparatus : A corridor-type distance maze having a wall of 30 cm high as shown in Fig. 1 was used. G 3 is the goal box (rewarded by three pellets 150mg) and in G 1, 2, 4, 5 there were just empty food dishes.
Procedure : After examining preference to G 15 the subjects were trained to go to G 3 without entering G 1, 2, 4, 5. Ten trials a day (inter-trial interval was 2' 15″) were done by a self-correction method. Entering directly into G 3 was the correct response and training criterion was ten continuous correct responses in a day. After training rats were divided into two groups, massed extinction (inter-trial interval is 15″) and spaced extinction group (inter-trial interval was 4' 15″). Each rat in both groups received forty extinction trials a day and the trial ought to finish in 3 minutes.
Results : Latency curves in extinction were compared in Fig. 2 and the frequency of various responses in Fig. 3 (massed group comprised eleven rats and spaced group ten rats, so the frequency of the former was corrected by multiplying by 10/11). Percentages of each of nine response types to the total responses for a day were compared in Fig. 4. Latencies are longer and responses to G3 are fewer in massed extinction, than spaced. In the other hand responses to G 1, 2, 4, 5 and Ds, R, L are more numerous and non-responses are fewer in massed extinction.
Conclusion : Various responses excepting the trained response occurred very often in massed extinction because the additive drive ΔD caused by non-reinforcement is conceived much more in massed extinction than spaced extinction. The responses to G 1, 2, 4, 5 similar to G 3 are due to directive function of ΔD and responses to Ds, R, L are relying on motivating function of ΔD. But inhibition increased much more in massed extinction because latencies are longer and responses to G 3 are fewer in massed extinction.

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Seventy rats were divided into three groups (GA, GB, and GC; each group was composed of two sub-groups). GA was subjected to four retests of HEBB-WILLIAMS test (1946 ; T₁, T₂, T₃, and T₄) separated by each of one month interval, GB was retested on T₁ and T₄, and GC was done on T₃ and T₄ (Table 1). Each S was held in its individual cage from 36 age in days. S was submitted to handling (4 days), familiarization (3 days), pre-training (3 days), general activity test (one trial on the elevated runway without reinforcement on the last day of the pre-training) and HEBB-WILLIAMS test (6 days). On the retest, pre-training, general activity test and the main test were given.
The results were summarized as follows.
1. The findings did not show the effect of facilitation due to maturation (Table 2), but the effect of repetition of test (Table 3).
2. GB did not show any improvement from T₁ to T₄ in terms of the number of errors (Table 4). This result seems to be attributed to curiosity drive or handling effect.

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[in Japanese]

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[in Japanese]

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