Cognitive Abilities and Social Behavior in Aged Japanese Monkeys

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1. Old high-ranking males tended to maintain continuously affiliative relationships with some adult females, and such relationships are useful for the old males to maintain their high dominance positions. Females are more likely to concentrate their social activities toward their close relatives, compared with younger females.2. The results of delayed response task show that the extremely aged females more than 30 years of age who could not survive in the wild are most heavily impaired in visuospatial memory and that post-reproductive females aged 25-29 years are next, while females in the first half of the twenties whose reproductive ability is decreasing can still maintain their ability which is as high as that for females aged less than 20.3. The presence of grandmothers is beneficial to their grandchildren's survival during the first year after birth in only high-ranking kin-groups.4. A gorilla mother's activities could be considered scaffolding for her young adult daughter with regard to maternal infant care.