The partial reinforcement effect (PRE) which is obtained after a small number of training trials can't be easily explained by the foregoing theories, since in these the crucial mechanisms of the PRE presuppose rather extensive trials. Thus a PRE-mechanism that is independent of the number of trials shoud be hypothesized. Capaldi interpreted the PRE in terms of the generalization of conditioned stimulus-aftereffect. The present study was conducted to determine whether this aftereffect-mechanism is independent of the number of training trials, employing a situation in which reward was partially delayed.
In Exp. I, extended training (48 trials) was used with 4 groups of rats;continuous reinforcement (CR), partial reinforcement (PR), 5 sec. partial delay of reinforcement (PD₅), and 40 sec. partial delay of reinforcement (PD₄₀). In Exp. II, the same design was used, but limited training (5 trials) was given. In each experiment, the subjects received a training and an extinction in a straight alley.
In two experiment, the PRE was obtained and the resistance to extinction increased as a function of the delay time of reinforcement (Fig. 1 and Fig. 3). The results of Exp. II show that CAPALDI'S prediction concerning the extinction process following the partial delay of reward is applicable even to the condition of fewtrial training, and combined with those of Exp. I, suggest that the generalization of stimulus-aftereffect was independent of the number of training trials. The applicability of CAPALDI'S stimulus-aftereffect hypothesis to the few-trial PRE was proposed.

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To examine increase in general activity through rearing in enriched environment, an experiment was performed with using 15 male rats and 12 female rats immediately after weaning. Nine experimental male animals were reared from 25 to 104-day-old in the enriched environment cage measured 1, 000 × 1, 000 × 450mm covered with wire netting (Fig. 1). Six control male animals and 12 control female animals were reared 6 in group in the standard laboratory group cage measured 410 × 270 × 150 mm covered with wire netting.
One hundred-day-old animals were subjected to 5 minutes DENENBERG (4, 5) type open-field test for 3 days. It was found that experimental male animals were significantly more active than the control male animals (Fig. 3, Table 1). Control female amimals were also significantly more active than the control male animals (Fig. 3, Table 2). Control female animals ambulated as equally as male control, however, in the first test day. Their activity increased significantly as the test day proceeded. Sex × test days interaction was also significant. There was no significant enrichment effect in open-field defecation and urination scores (Table 3, Table 4).
On fourth and fifth days, behavior was measured in the activity wheel for 20 minutes. Although it did not reached level of significance, experimental male animals were more active than control male (Fig. 5). Enrichment × test days interaction was significant. Control female ran extremely greater than the control male and the difference was highly significant. Lastly, the growth curve of weight indicated that control male were heavier than experimental male (Fig. 2).
In discussion, reasons for contradictory result of SMITH (29), namely control rats were more active in open-field test, were considered. It was pointed out that SMITH (29) restricted control animals in individual cages. Restriction increases also open-field activity as MELZACK (19, 20), FUJITA and HARA (7) and MITANI (24) 's results.
It was concluded that “enrichment” increases general activity, namely psychologically positive activity, and “restriction” produces hyperactivity, namely psychologically negative activity. This suggestion is also found in WHIMBEY and DENENBERG (32) 's two factor theory of open-field activity and MITANI (23, 24) 's implication.

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This experiment was designed to test the relative efficiency of color and form as cue with which Japanese monkeys can learn oddity problems.
In the training periods, 4 Japanese monkeys were trained on 3-position oddity problems using stimuli shown in Fig. 1 and Table 1 with a modified WGTA. Six kinds of stimuli were used and they were divided into 3 groups of 2. Combinations and permutations of stimuli of 3 groups provided 18 different spatial configurations, which were randomly presented 4 times a day. A correction method was used. After criterion (more than 80% correct responses, 2 successive days) had been attained, monkeys were subjected to color-form cue dominance test on ambiguous oddity problems.
In the test periods, each S received 96 trials a day for 6 days. A test trial was inserted every 4th trial. On a test trial, an ambiguous stimulus was substituted for one of the identical stimuli and it yielded two separate solutions arrived at by using two independent cue dimensions. For example, from left to right the stimulus objects might be a red ball, a red ball and a blue green cross on an original training trial, one of the red balls was changed to a blue green ball (ambiguous stimulus) on a test trial. A food reward would be obtained either by a color choice (red ball) or by a form choice (blue green cross) (1, 2, 3 in Fig. 3). On ambiguous oddity problems, there are 72 possible stimulus configurations, one third of which were randomly presented a day for 3 days. And the same procedure was duplicated.
The learning processes of 4 Japanese monkeys on simple 3-position oddity problems are illustrated in Fig. 2. Results of testing support the previous findings that color is a more effective cue than form for macaque monkeys to solve oddity problems.
Subsequently monkeys were given simple 3-position oddity problems which consist of the possible combinations of unidimensional stimuli shown in Fig. 1. Color-oddity problem and form-oddity problem were randomly presented 72 trials a day for 3 days. In this test, the transfer effect to these problems from previous oddity training was observed (Fig. 2, Table 3), and it was found again that in these simple oddity situations color cue is more dominant than form cue.

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Albino rats were tested for approach and eating behavior on a floor on which they previously received shocks, in order to ascertain whether or not the presence of an anesthetized rat could induce eating behavior in the S_S. However, at the time of the test, the grid was not electrified. The results indicated that the mere presence of an anesthetized rat could not induce approach behavior to the food cup. However, an anesthetized rat placed near the food cup could at least induce approach behavior to the food cup. Further, a demonstrator rat which ate rice grains induced more consumption of rice grains in the S_S.

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