Executive function mediates age-related variation in social integration in female vervet monkeys (Chlorocebus sabaeus).

ABSTRACT

In humans, social participation and integration wane with advanced age, a pattern hypothesized to stem from cognitive or physical decrements. Similar age-related decreases in social participation have been observed in several nonhuman primate species. Here, we investigated cross-sectional age-related associations between social interactions, activity patterns, and cognitive function in 25 group-living female vervets (a.k.a. African green monkeys, Chlorocebus sabaeus) aged 8-29 years. Time spent in affiliative behavior decreased with age, and time spent alone correspondingly increased. Furthermore, time spent grooming others decreased with age, but the amount of grooming received did not. The number of social partners to whom individuals directed grooming also decreased with age. Grooming patterns mirrored physical activity levels, which also decreased with age. The relationship between age and grooming time was mediated, in part, by cognitive performance. Specifically, executive function significantly mediated age's effect on time spent in grooming interactions. In contrast, we did not find evidence that physical performance mediated age-related variation in social participation. Taken together, our results suggest that aging female vervets were not socially excluded but decreasingly engaged in social behavior, and that cognitive deficits may underlie this relationship.