Thirty-nine rats were run in a runway in order to examine the partial reinforcement effect under four conditions : Both 100 percent 40 reinforcement group and 100 percent 20 reinforcement group did not show the partial reinforcement effect. But both 50 percent running partial reinforcement group and 50 percent non-response extinction group, where the Ss run through the runway to find food 50 percent of the trials and directly placed in the goal box to find no food the remaining 50 percent of the trials, did clearly show the more resistance to extinction than the both 100 percent groups. The result of 50 percent nonresponse extinction group does not support the results of THEIOS and POLSON'S (10).
Some theories on the partial reinforcement were discussed in relation to the present experiment.

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The purposes of this experiment were as follows; 1) to test whether learning of imitation and learning through imitation are possible or not, and 2) to compare the effect of learning through imitation with that of trial and error learning. Thirty three albino rats were trained to follow a leader rat to obtain reward on the elevated T maze. These trainings were given to them 10 trials per a day for 15 days. After these trainings, followers were divided into three groups. Group LOI (learning of imitation) learned just to follow the leader. Group LTI (learning through imitation) learned the response to the light-on cue through following the leader who had been previously trained to discriminate the light-on cue. Group TAE learned it by trial and error procedures without any leader. These trainings were given to followers 10 trials per a day for 11 days. On the 5th, 10th and 11th day, followers of all groups were run the maze without any leader but only with the light stimuli. The results were that the learning of and through imitation were both possible in white rats. These results confirmed the previous experiments by MILLER and DOLLARD, and CHURCH. There were tendencies that learning through imitation was a little more efficient than trial and error learning.

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It is supposed that the concept of “discrepancy” plays an important role in the discussion of the exploratory behavior. Discrepancy is defined as difference between past stimulation and present stimulation. That is, stimulus change, novelty and complexity are little more than discrepancy. In two experiments reported here, discrepancy was produced by means of stimulus adaptation and it is designed to investigate the effect of the discrepancy upon the exploratory behavior in the rat.
The apparatus used was two-choice situation composed of Room S and Room C. Room C differed from Room S in having more luminosity, checkered pattern and the fixed panels (see Fig. 1). The experiment of each consisted of two stages, i. e. the adaptation period and the exploration period, and had four groups, i. e. Group S, C, SC and NSC. In Experiment 1, Group S was adapted for Room S, Group C for Room C, and Group SC for both Room S and C for 15 min. per day for 5 days. Group NSC was not adapted for the apparatus, but for the detention cage. After 24 hours from the last adaptation, all subjects received free exploration for 10 min. per day for 3 days. In Experiment 2, the subjects were adapted for the apparatus for 75 min. within a day. Immediately after this period, free exploration was allowed for 10 min. for 3 days. Three response measures were used during the exploration period, i. e. starting latency, time spent in Room S and C, and the first choice of the room. In addition, the number of defecation during the adaptation period was measured.
The results were as follows :
1. In both experiments, the number of defecations during adaptation period didn't decrease in Group SC, while the other three groups decreased (Fig. 2 and 5). This fact might suggest that discrepancy aroused emotional response especially in the Group SC in which discrepancy was produced both within a day and between days.
2. The starting latencies decreased as the subjects explored the apparatus in both experiments (Fig. 3 and 6). Especially in Group SC which explored Room S and C during adaptation period the latency was the shortest, while Group NSC which had no experience to explore the apparatus showed the longest latency. This results might also indicate that discrepancy produced emotional behavior in the exploratory situation.
3. In Experiment 1, Group S and SC spent more time in Room S than in Room C, and in Experiment 2, all groups spent more time in Room S (Fig. 4 and 7). It might be suggested from these results that Room C was aversive for the rat. It is to be noted, however, that in Experiment 1 the time spent in Room S decreased in Group S as the subjects explored the situation, but the time spent in Room C increased. It might seem that discrepancy functioned negatively in the first day of free exploration, but later functioned positively.
4. In both experiments Group S changed significantly their first choice from Room S to Room C during exploration period. This result might also suggest ambivalence of discrepancy.

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The purpose of this experiment was first to investigate whether rats discriminate between oblique lines or not, and secondly to examine the transfer from the discrimination of oblique lines to that of pairs of symmetrical figures;_??_ and _??_, _??_ and _??_, and so on.
Ss were 30 naive male white rats. Twenty four out of 30 animals were assigned to experimental groups, and 6 animals were assigned to control groups. The apparatus was a modified jumping stand (Fig. 1). In experimental groups S was given 20 trials per day to discriminate between oblique lines (Fig. 2) by correction method. This initial training continued until a criterion of 18/20 correct responses with 9 correct responses out of the last 10 trials within a day had been attained.
Following initial training, test session was given to S successively. During this period, S had to receive 10 trials of initial training prior to each transfer test within a day. When S responded correctly in these all 10 trials of initial training, S was given a transfer test within a day, and when S committed no less than one error in 10 trials, S continued to respond until the criterion of initial learning had been attained and the following day all responses of consecutive 10 trials had been correct. Each transfer test consisted of 20 trials, and the both of responses to the test stimuli were baited. As shown in Fig. 2, there were 6 kinds of transfer test, 4 kinds of which were designated as a sequence. A sequence was given to each S. To counterbalance sequential order of 4 kinds of test, the 8 ways of sequence were arranged as follows. (1) N-1, N-2, Z-1, Z-2, (2) N-1, N-2, Z-1', Z-2, (3) N-1', N-2, Z-1, Z-2, (4) N-1', N-2, Z-1', Z-2, (5) Z-1, Z-2, N-1, N-2, (6) Z-1, Z-2, N-1', N-2, (7) Z-1', Z-2, N-1, N-2, (8) Z-1', Z-2, N-1', N-2. And 3 animals were assigned to each of 8 sequences.
Results of initial learning : all Ss in experimental groups could discriminate pairs of oblique lines, and the mean number of trials to the criterion in initial learning was 387. 5.
Results of transfer tests : the response to the stimulus, a part of which has been correct stimulus in initial learning, was recorded as correct response in tests. The mean number of correct responses out of 20 trials in each test are shown in Table 1. All conditions in tests indicated positive transfer, with individual differences in some conditions (Table 1).
Ss in the Z-1'of transfer test (1) showed significantly less correct responses than Ss in the Z-1 and N-1'. Though there were statistically no differences among 4 groups in transfer test (3) (Table 1), the same tendency as test (1) was found.
Three animals out of the 6 rats of control groups were trained to discriminate between _??_ and _??_ without training to the oblique lines, and the other 3 were trained in the same way except training between _??_ and _??_. Ss in both control groups could not discriminate the symmetrical pairs of these stimuli.
Thus we make clear that Ss can discriminate between oblique lines, though it is not obvious whether Ss can discriminate in terms of the total pattern made by the shape or in terms of orientations, and show positive transfer in all tests, with individual differences in some conditions.

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[in Japanese]

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