title: Dominance rank causally affects personality and glucocorticoid regulation in female rhesus macaques.
abstract: Low social status is frequently associated with heightened exposure to social stressors and altered glucocorticoid regulation by the hypothalamic-pituitary-adrenal (HPA) axis. Additionally, personality differences can affect how individuals behave in response to social conditions, and thus may aggravate or protect against the effects of low status on HPA function. Disentangling the relative importance of personality from the effects of the social environment on the HPA axis has been challenging, since social status can predict aspects of behavior, and both can remain stable across the lifespan. To do so here, we studied an animal model of social status and social behavior, the rhesus macaque (Macaca mulatta). We performed two sequential experimental manipulations of dominance rank (i.e., social status) in 45 adult females, allowing us to characterize personality and glucocorticoid regulation (based on sensitivity to the exogenous glucocorticoid dexamethasone) in each individual while she occupied two different dominance ranks. We identified two behavioral characteristics, termed 'social approachability' and 'boldness,' which were highly social status-dependent. Social approachability and a third dimension, anxiousness, were also associated with cortisol dynamics in low status females, suggesting that behavioral tendencies may sensitize individuals to the effects of low status on HPA axis function. Finally, we found that improvements in dominance rank increased dexamethasone-induced acute cortisol suppression and glucocorticoid negative feedback. Our findings indicate that social status causally affects both behavioral tendencies and glucocorticoid regulation, and that some behavioral tendencies also independently affect cortisol levels, beyond the effects of rank. Together, they highlight the importance of considering personality and social status together when investigating their effects on HPA axis function.
authors.affiliation: Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30322, USA. Electronic address: jnkohn@emory.edu.
authors.forename: Jordan N
authors.initials: JN
authors.lastname: Kohn
authors.affiliation: Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA; Duke Center for Aging, Duke University, Durham, NC, 27708, USA.
authors.forename: Noah
authors.initials: N
authors.lastname: Snyder-Mackler
authors.affiliation: Department of Pediatrics, Sainte-Justine Hospital Research Centre, University of Montreal, Montreal, Quebec, H3T 1C5, Canada.
authors.forename: Luis B
authors.initials: LB
authors.lastname: Barreiro
authors.affiliation: Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30322, USA; Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA.
authors.forename: Zachary P
authors.initials: ZP
authors.lastname: Johnson
authors.affiliation: Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA; Department of Biology, Duke University, Durham, NC, 27708, USA; Institute of Primate Research, National Museums of Kenya, Nairobi 00502, Kenya; Duke Population Research Institute, Duke University, Durham, NC, 27708, USA.
authors.forename: Jenny
authors.initials: J
authors.lastname: Tung
authors.affiliation: Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30322, USA; Department of Psychiatry & Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, 30322, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Wilson
mesh_terms: D000818:Animals; D001007:Anxiety / Q000378:metabolism / Q000523:psychology*; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism / Q000502:physiology*; D008253:Macaca mulatta; D023421:Models, Animal; D010551:Personality / Q000502:physiology*; D010913:Pituitary-Adrenal System / Q000378:metabolism / Q000502:physiology*; D012930:Social Dominance
chemical_list: D006854:Hydrocortisone
keywords: Animal personality; Dominance rank; Hypothalamic-pituitary-adrenal axis; Nonhuman primates; Psychosocial stress; Social subordination