Open-field behavior of 99 male mice from seven inbred strains, A/J, AKR/J, BALB/c, CBA/J, C3H/He, C57BL/6 and DBA/2J, was measured for one hour to compare locomotor activity, defecation and urination among them. The time course of activity was basically the same in all strains, to increase in the level during the first prart of the test and then to decrease afterward, making a definite inverse U-shaped curve more or less. C57BL, DBA, CBA and AKR showed much more rapid increase during the first 15-20 minutes and gradual decrease in activity than A, BALB and C3H. Albino strains, typically BALB, tended to make more elimination (defecation and urination) than the pigmented. Activity had significant but weak negative correlations with elimination. The values of around -0.3 are comparable to those in many open-field studies in the past.

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Four chimpanzee mother-infant pairs belonging to Tama Zoological Park were observed in order to see how this relationship develops. The main study run from August 1986 to December 1989. Each mother-infant pair was observed for 30 minutes once a week. All behavior patterns were recorded and analyzed.
The data showed that the process of the chimpanzee infant's development of attachment resembled closely that of humans from the pre-attachment-phase to a goal-corrected-partnership (Bowlby's model 1969). Moreover, three or four-year-old chimpanzee infants seemed to have some conflict with their mother, because ambivalent behavior occurred at that time. Infants whimpered for their mother without cause for fear and soon after the mother held them, they left her and whimpered again. Such ambivalent behavior patterns towards the mother are often observed in human infants.

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In four experiments, two adolescent chimpanzees were given an object-sorting task to assess their categorizing ability. In Exp. 1, they were presented a set of two identical objects (AA) and one odd (B) object, and trained to sort the objects in two categories, AA and B ; four kinds of objects were used in training. They learned this type of sorting easily. In Exp. 2, 3, and 4, test stimulus sets were inserted in random positions among the baseline sets of Exp. 1. In test trials, the test sets differed for each trial, and the chimpanzees always received food regardless of how they sorted. In Exp. 2, test sets were novel objects. In Exp. 3, the ebjects in each test set were identical either in color or in shape, and could be sorted based on the other dimension. In Exp. 4, the objects in each test set were different, and could be sorted based on either color or shape. In test trials of Exp. 2, 3, and 4, chimps sorted categorically and their performances were highly significant. The implications of these results are discussed.

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[in Japanese]

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