The number and weight of fecal boluses in the home cages (HC) of Maudsley reactive (MR) (6 males and 6 females) and nonreactive (MNR) (6 males and 6 females) strains of rats were recorded for four days. They were also given the open-field (OF) test of emotionality. The MR rats defecated significantly more in the OF situation than the MNR rats, but there was no tendency for the MR rats to defecate more in the HC than the MNR rats. The OF defecation score proved to be independent of the HC defecation score. Other HC measures and OF measures were recorded. Generally the results were in line with the previous findings.

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A large amount of data has been reported in recent years concerning the interaction of a given condition of reinforcement and previous or contemporary conditions of reinforcement. This interaction has been commonly referred to as “behavioral contrast”. In this paper, it was tested whether the contrast effect was obtained in the discrete trial situation in terms of running behavior and behavior variability.
Of two experiments reported here, Exp. I was concerned with simultaneous contrast effect, while Exp. II with successive contrast effect. The apparatus used was one pair of T maze. Except a start box and goal boxes, one maze was painted white (S₁) and the other black (S₂). A start box and goal boxes were painted gray in both mazes.
In Exp. I, Ss were randomly assigned to five groups of 10, each. The groups, defined in terms of the percentage of reinforcement administered in their positive and negative mazes, respectively, were; Group I (100%-100%), Group II (100%- 50%), Group III (100%-0%), Group IV (50%-50%), Group V (50%-0%). After exploration and pretraining, all Ss were given 21 successive free-choice trials per day in two T mazes for 10 days.
In Exp. II, Ss were divided into four groups of 10, each. The groups were; Group I (100% control), Group II (100% downshift), Group III (30% control), Group IV (30% upshift). During first 5 days of training, Groups II and IV received identical treatment with Groups I, III, respectively. Subsequently in Group II, percentage of reinforcement of S₂ were shifted from 100% to 30% during Days 6 to 15. On the contrary, Group IV received upshift of S₂ from 30% to 100%.
Three response measures were employed in both experiments, i. e., starting latency, running time and choice direction.
The results were as follows :
1) In Exp. I, the result of starting latency indicated a significant evidence for the positive contrast effect. That is, the starting latency in the 100% maze was shortest for Group III, intermediate for Group II and longest for Group I (Fig. 1). Though there was statistically no difference among 3 groups in running time, the similar tendency was found.
2) The choice behavior significantly differed among 5 groups. Although Groups I and IV tended to chose the same side with about equal frequency at the end of training, the Ss subjected to the differential conditioning (Groups II, III and V) preferred one side in 100%, maze and avoided that side in, the other maze (Fig. 2). This fact would suggest that some difference in percentage of reinforcement tends to fixate the choice behavior and these tendencies result from behavioral contrast effect.
3) Unlike Exp. I, Exp. II showed no evidence of contrast effect. The successive shift of percentage reinforcement of S₂ did not result in any change in response time (Fig. 3) and choice behavior. It would be shown from the present experiments that behavioral contrast effect was observed in the simultaneous shift of percentage of reinforcement, but not in the successive shift.

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1. Determination of EEG Patterns in Sleep
An experiment was performed to determine relations of EEG patterns in natural sleep with arousal level. 6 male albino rats, 7.5 to 11 months after birth, were used. Stainless steel electrodes were implanted chronically in occipital cortex and hippocampus. EMG recordings were obtained from the neck muscle. By inspection of the polygraphic data based on EEG, EMG and behavior, 7 patterns were classified (Fig. 1). Patterns A and B indicate arousal states. Patterns C and E indicate drowsy or light sleep states. Patterns F and G indicate deep sleep states. Pattern H indicates paradoxical sleep.
2. Stimulation Experiment
In this experiment 4 rats were used. Pure tones (4000 cps, 1 sec. strong = 95 phon, weak =87 phon) were given to the animals when each EEG pattern appeared. It was assumed that tone stimulation would heighten arousal level.
Fig. 3 and 4 show EEG pattern change by auditory stimuli during stimulation, post stimulation I (0-3 sec. after stimulation), post stimulation II (3-7 sec. after stimulation). Auditory stimulation changes deep sleep (F, G) and paradoxical sleep (H) EEG patterns to light sleep (C, E) patterns during stimulation or post stimulation I. But during post stimulation II, light sleep patterns changes to deep or paradoxical sleep patterns again.

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Examining WALKER'S (16) “action decrement” theory, four experiments on spontaneous alternation were performed.
In Experiment 1, animals rewarded with 1 pellet in a T maze alternated more than animals given 8 pellets in a series of 2 trials a day over 13 days (Fig. 1).
To correct the weak point of Experiment 1-namely that the 1-pellet animals would be subject to greater stimulus satiation in the goal box-in Experiment 4, three degrees of sucrose concentration in water were used as rewards under no thirst drive condition. It was found that after the first trial, higher sucrose concentrations were accompanied by a higher rate of alternation but by a decrease in latency and running time (Fig. 5, Table 2). Moreover, the average running time of alternating animals was shorter than that of repeating animals (Fig. 6). Adding the data of Experiment 2 (Fig. 2), in which animals were under a thirst drive, a significant reward × drive interaction was found (Table 1).
In Experiment 5, the massed 11 trials method produced different results from those of Experiment 4 (Fig, 7).

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[in Japanese]

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