An experiment which analyzed the dominance order of four male crickets and the influence of social inversion. The Ss were paired with each other in encounters in order to obtain a dominance order. Once the order was determined the Ss were taken out from the group, starting with the Alpha and going down to the Delta animal, until all animals were inverted into the new group. The inverted group remained dominated by the same animal as in the original group. One cricket (IV) showed an increase of 26% in the amount of total wins. The increase was explained as a result of : 1) IV was the last animal to be inverted ; 2) going into battle with II and III, IV was coming off from isolation and a previous win-an advantage in his favor, and 3) IV was molting during the time of the encounter. Results indicated that the dominance order in the original group and the order in the inverted group were similar although certain differences were noted.

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In order to investigate the effects of imitation, cats were placed in the experimental situation that both the demonstrator and the observer press a lever for food reward at the same time. The Ss of observer were tested under five different experimental conditions. Group 1 observed the demonstrator's lever pressing response, while the lever and foodcup were mounted in the same direction. Group 2 was the same as Group 1, except that the lever and foodcup were mounted in the opposite direction. Group 3 observed the demonstrator's feeding behavior, while the lever and foodcup were mounted in the same direction. Group 4 was the same as Group 3, except that the lever and foodcup were mounted in the opposite direction. Group 5 observed the demonstrator placed in the demonstrator box without the lever and foodcup. The results revealed that Group 1, 2, and 3 were superior to Group 5, and that Group 4 was inferior to Group 5. These results were interpreted to show that approach to the situation of demonstrator's behavior was an important factor, but that imitation played an important part as well.

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It has been reported that animals trained in a maze-type apparatus develop maximizing more rapidly than those trained in a Skinner type one. Besides, in the former apparatus a longer inter-trial interval and a smaller number of trials per day are usually used than in the latter one, which may also account for the above difference. The present experiment was designed to investigate rats' performance in a probability learning situation with the above two variables equalized for both apparatus.
Two groups of rats were trained on a spatial 75 : 25 probabilistic schedule for 920 trials using correction method. One group was trained in a T-maze and the other in a 2-lever Skinner box. Inter-trial interval was 13 sec. and the daily number of trials was 40.
Fig. 1 indicates that the T-maze group showed maximizing in only a few hundred trials, while the Skinner-box group remained at a matching level even after 900 trials. Table 1 shows the individual data. The difference between groups was significant (U=21, p<. 05).
These results replicated those of previous studies. Therefore, the difference in performance between apparatus conditions can be attributed to neither inter-trial interval nor the number of trials. The remaining procedural difference is that Ss trained in the T-maze were removed from the apparatus after each trial, while those in the Skinner box were not. This may have produced the present results. This possibility remains to be examined.

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[in Japanese]

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