Age-related variation in physical and social cognition in Barbary macaques (Macaca sylvanus)

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By 2050, a fifth of the world's human population will be over 60 years old. Because of the enormous impact on society, the physiological basis of aging, as well as the causes of cognitive decline, including Alzheimer's disease and dementia, have been at the core of major research programmes for several decades. More recently, general changes in the motivational disposition of aging individuals, as well as the consequences for the social fabric of a society have attracted increasing attention. In the proposed study, we take a comparative perspective to investigate the biological basis of social and cognitive aging processes. We will conduct behavioural observations and cognitive tests in Barbary macaques (Macaca sylvanus) at the monkey enclosure La Foret des Singes in France. Building on previous work (Almeling et al. 2016, Curr Biol), where we revealed decreasing performance in problem solving, as well as shifts in social preferences with age in this species, we here aim to investigate the foundations of these effects in more detail. Specifically, we aim to conduct a series of cognitive tests with the same study group of Barbary macaques, to assess variation in inhibitory control, cognitive flexibility, and persistence with age. In addition, we aim to test whether old monkeys show a positivity effect (as humans do), i.e. a preference for positive stimuli and interactions. To this end, we will present the monkeys with pictures of affiliative and agonistic facial expressions; further, we will record the exchange of social signals in interactions. These behavioural observations will also allow us to explore age-related variation in social network size and structure in males, which have not been studied in this context. Our study has the potential to provide important comparative data for a better understanding of social and cognitive aging, and to further forge ties between evolutionary biology and human life-span research.