The short history of learning set (LS) research was reviewed for the purpose of elucidating the present state of our knowledge of the subject. The following remarks were made : (1) Disproof of the uniprocess theory and the revised understanding of the transfer suppression greatly reduced the plausibility of Harlow's error-factor theory of LS. (2) Discovery of the equivalence of successive-reversal training and LS training, also disclosing another weakness of the error-factor theory, led to the acceptance of Levine's model as an alternative theory of LS. (3) Bessemer and Stollnitz elaborated basic ideas of the model and, introducing a distinction between error-factor effects and hypothesis learning, formulated a new version of hypothesis theory of LS. (4) Subsequent experimental studies examining transfer effects of overtraining and successive informed-reversal training tested implications of the theory and revealed flaws and restrictions of the theory. (5) These studies also provided evidence for believing the occurrence of attention learning during LS training. Both hypothesis and attention learning seem to contribute to the formation of LS.

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In order to investigate whether the response duration covaries with varying of the response rate, we trained four rats to press each of two levers on a variety of concurrent variable-interval schedules of reinforcement and punishment. Reinforcement condition consisted of five schedules of reinforcement using food. When the response rates fell within a given range on each of reinforcemcnt schedule, a punishment schedule using an electric shock was added to that reinforcement schedule. Five different schedules combining reinforcement and punishment comprised the punishment condition. We employed the local response rate which refers to the number of responses per minute on each lever, and the response duration which refers to the mean duration that rat pressed down the lever.
The results indicated that only in the punishment condition, the response duration negaitively correlated with the response rate. These results implied that the response rate alone does not entirely describe the response strength in the punshment condition. We further discussed validity of the suppression ratio. We suggest that both temporal behavioral measures and traditional response rates are necessary for precise description of the behavioral suppression.

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The emergence from a home cage in rats (Rattus norvegicus) was investigated as a function of strain and sex. Both sexes from the Donryu/Hos, Long-Evans, Sprague-Dawley/Crj (CD), Wistar/Crj, Wistar-Imamichi/Iar, F344/DuCrj, and the Tsukuba High-and Low-Emotional strains (THE and TLE) were employed as subjects. It was found that the Long-Evans and THE were the two extremes. That is, all the Long-Evans rats emerged from the home cage, whereas none of the THE did. Females emerged more frequently than males. These results were discussed in terms of emotionality and activity.

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