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Dryad

Repeatability of measures of biobehavioral organization over two years in captive infant rhesus macaques, Macaca mulatta

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Jan 22, 2024 version files 68.04 KB

Abstract

Individual differences of infant temperament have been associated with future health outcomes that provide explanatory power beyond adult personality. Despite the importance of such a metric, our developmental understanding of personality-like traits is poor. Therefore, we examined whether young primates show consistency in personality traits throughout development. We replicated a Biobehavioral Assessment (BBA) at three time periods: 3-4 months, one year, and two years of age in 47 rhesus macaque (Macaca mulatta) subjects from large mixed-sex outdoor social housing units at the California National Primate Research Center. We report results for tests focused on responses and adaptation to the temporary separation and relocation, responses to a threatening stimulus, and ratings of overall temperament. We found consistently repeatable associations in measures of Emotionality; these associations were stronger in males, but also present in females, and broadly consistent between year one and two. We also explored whether behavioral responses to this experimental relocation might be influenced by their experience being relocated for other reasons (i.e., hospitalizations) as individuals’ responses might be influenced by similar experiences to the BBA procedure. Only locomotion, during one of the assessments, was associated with past hospitalization events. Overall, repeatability in Emotionality-associated behaviors was evident across the two years, in both sexes. We did, however, find evidence of the emergence of sex differences via differentiated expression of behavioral responses during the BBA. We emphasize that there is likely contextual nuance in the use of these BBA factor-associated behaviors. Further research is required to determine whether and how shifts occur in underlying factor structure and the expression of associated behaviors.