UC Davis

Older adults (> 65 years old) make up an ever-growing percentage of the global human population. This demographic shift is among the most pressing public health concerns of our time due to the unique health challenges that older adults face. Although aging is clearly detrimental to some aspects of physical health and mental ability, relatively less work has evaluated how aging impacts social and affective (socioaffective) processing, despite the important role these two fundamental aspects of our lives play in determining our health and wellbeing. The existing literature shows the somewhat paradoxical finding that aspects of people’s socioaffective processing improve with age—though in whom and for what reasons remain an open question. Understanding sources of variation in socioaffective aging trajectories will help promote wellbeing for those who are most in need. Although most research on socioaffective aging to date has taken place in humans, adopting a comparative approach will illuminate novel psychological, physiological, and social mechanisms through which changes to socioaffective processing occur and speak to the evolutionary origins of such changes. Here, I investigate how aspects of socioaffective processing differs across the lifespan in rhesus monkeys (Macaca mulatta), which share key features of human developmental neurobiology, physiology, and social behaviors. In Chapter 1, I evaluate age-related differences in visual attention towards faces of conspecifics ranging in affective content to test the hypothesis that aging influences how monkeys process affective stimuli. Consistent with work in humans, I find that while middle-aged animals display robust biases in visual attention towards threatening faces, aged animals show no such bias, suggesting phylogenetically conserved mechanisms of age-related threat avoidance. Chapter 2 evaluates age-related differences in monkeys’ autonomic nervous system responsivity towards social stimuli and finds age-related disruption to how the parasympathetic nervous system of aged monkeys responds to such socioaffective stimuli. These disruptions to the parasympathetic nervous system may specifically serve as a driving force behind changes so primate social behavior in aging. Finally, Chapter 3 adopts a large-scale lifespan approach to assess how features of infant monkeys’ behaviors and social environments predict risks mortality rates across 20 years of follow-up. We find infant reactivity and social environments predict morality rates across their lives, with adolescence and old age being particularly sensitive windows of development. Together, these investigations speak to the important role social and affective processing plays in health and wellbeing throughout the primate lifespan and how age-related changes in psychosocial processing and behaviors may serve to promote longevity.