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2021 Abstracts

Behavioral Inhibition in Infant Nonhuman Primates

Presenters: Colt Halter, College of Family, Home, and Social Sciences, Psychology
Authors: Colt M. Halter, Elysha Cash, Elizabeth K. Wood, William W. Thompson, and J. Dee Higley
Faculty Advisor: Dee Higley, College of Family, Home, and Social Sciences, Psychology
Institution: Brigham Young University

Studies in human children show that behavioral inhibition (BI) is stable over time, has biological underpinnings, and predicts later life outcomes. Kagan’s now-classic studies of BI used a standardized paradigm, where subjects are exposed to an unfamiliar playroom with a variety of novel, interesting stimuli and an unfamiliar peer. While many studies have investigated BI in nonhuman primates, none have used the identical paradigm that Kagan used to study children. To remediate this, the present study translates the original Kagan paradigm for use in nonhuman primates. Nursery-reared rhesus monkeys were assessed at 30 days of age (N=12) for BI using the Infant Behavior Assessment Scale. When subjects were four months of age, they were twice-assessed in a novel playroom using methodology similar to that used by Kagan to study human infants, measuring behaviors characteristic of an inhibited monkey, as well as vagal tone and plasma cortisol concentrations. Results showed that high ratings for BI at 30 days of age was predictive of BI in the playroom at four months of age, with high BI at 30 days of age predicting limited time socializing with peers, and more time in anxiety-like freezing. When compared to subjects low in BI, they also showed less time exploring the environment, during the second session. Infants with low vagal tone showed higher locomotion and lower self-clasping, and reduced freezing and more social behavior in the second Kagan session. In addition, cortisol levels obtained immediately after each session positively predicted levels of environmental exploration, locomotion, and social behavior. Taken together, when using a paradigm fashioned after that used by Kagan to study human children, these findings parallel those seen in human children, suggesting an evolutionary conserved temperamental trait and that rhesus monkeys possess high utility as translational models for the assessment of human behavioral inhibition.