My main research interests are focused broadly on the causes and consequences of social relationships in nonhuman primates. I've taken several approaches to exploring these issues.

Behavioral, physiological and health consequences of social relationships. The first approach has been to utilize an animal model of human AIDS to study the health consequences of social relationships. Infection of rhesus macaques with the simian immunodeficiency virus (SIV) is the principal animal model for human AIDS. In collaboration with Drs. Sally Mendoza, William Mason, and Nicholas Lerche, we showed that monkeys that experienced stable social relationships survived significantly longer following SIV inoculation compared to animals that experienced social stress. Differences were found in behavioral responses, in viral and immune measures, and in concentrations of stress-related hormones. Thus, stable social relationships appear to exert protective effects in this disease context. I reported these results, as well as others obtained in a large retrospective study, in two major papers published in 1998 in Proceedings of the National Academy of Sciences, and in Psychosomatic Medicine.

This line of research has been informed by a very productive collaboration, begun in 1990, with Dr. Gregory Herek. In this program, we have been examining Americans' attitudes toward AIDS and people with AIDS. In a number of significant publications we have documented the existence of widespread negative attitudes toward, and intentions to avoid, HIV-infected people. (The most recent paper in this series, in American Journal of Public Health, summarizes our eight years of public opinion data.) There has been speculation from early in the epidemic that psychosocial stress, arising from negative attitudes and avoidant behavioral intentions (among other sources) might account for some of the wide variability seen in rates of AIDS disease progression. My primate work allowed me to address this issue in an experimental setting, and supported the idea that variation in rates of disease progression are related to social experiences.

Contribution of personality traits to behavioral and physiological outcomes. The SIV research identified factors that influence how animals adapt to social situations and form social relationships. Having been intrigued by some research conducted in the 1970s that demonstrated the existence of stable personality dimensions in rhesus monkeys, we assessed personality in our monkeys 1.5 years prior to the start of the SIV study. We found that one personality dimension, Sociability, appeared particularly influential in the monkeys' behavioral (Capitanio, 1999) as well as physiological (Capitanio, Mendoza, Baroncelli, 1999) responses to our social manipulations - animals higher in Sociability displayed better antigen-specific antibody and viral responses in the first 10 weeks of our study. We have been exploring further this personality dimension in a variety of situations. For example, recently we contrasted low- and high-Sociable animals' responses to the presentation of a standardized social stimulus - color videotape presentations of unfamiliar animals displaying social and nonsocial behavior (the paper describing these data is in press at Primates). When our subjects viewed tapes of animals displaying threatening gestures, their first response was usually to avert their gaze. This is an adaptive response in this species inasmuch as direct eye contact usually conveys a threatening intent. What was interesting, however, was that low-Sociable animals stared at the display nearly twice as long prior to gaze averting compared to high-Sociable monkeys. This suggests to us that low-Sociable animals may have some deficiency in social skills (rather than simply low social motivation), and when placed in a situation where they must interact, are more likely to have difficulty constructing affiliative social relationships. This may translate into a pattern of physiological reactivity that could have negative consequences for health.

This line of research - explorations of stable individual differences in personality and temperament in rhesus monkeys - is becoming of increasing interest to primatologists. Given that human studies of personality have demonstrated moderate heritability coefficients, there is interest in exploring the idea of species differences in personality and temperament to help understand the evolution of the 19 species of macaques (genus Macaca). The social evolution of macaques was the topic of a conference held in March 2001 (International Workshop on Macaque Societies and Evolution, held at the University of Mysore, India), and a paper addressing this issue is in the works.

Because this research is focused on what things are stressful to animals, and how individuals vary in their responses to such events, our research program has also been of interest to colony managers, and animal husbandry and animal welfare groups. As part of this research we have conducted studies demonstrating how blood sampling procedures affect certain hematological measures (Capitanio, Mendoza & McChesney, 1996), and how common laboratory procedures, such as housing relocation (Capitanio & Lerche, 1998), short-term physical restraint (Capitanio, Mendoza & Lerche, 1998) and training of animals to cooperate in phlebotomy (Bentson, Capitanio & Mendoza, submitted) affect stress-related outcome measures.

Characterization and consequences of individual differences in personality/temperament in infant monkeys. A new research direction has involved a more developmental focus. We are engaged in a Primate Center-wide assessment project to document the variability that exists in personality, temperament, and emotionality in three-month-old rhesus monkeys. We will assess up to 350 animals per year, with the goal of following these animals to determine how this variability relates to later health and social outcomes. This project not only has important theoretical value, but will provide practical information to colony managers to help them make better decisions about animal use.

Neurobiological contributions to social behavior. Finally, I've been involved in a collaboration with Dr. David Amaral during the past several years that has explored the role of the amygdala in social processes in rhesus macaques. Using state-of-the-art lesioning techniques coupled with a sophisticated approach to assessing social capabilities, we've shown that, contrary to some earlier research, amygdala lesioned animals display increased affiliative social behavior and are perceived as more attractive by non-lesioned control animals. These studies suggest that the amygdala may act as a 'brake', contributing to a species-normal reluctance to interact immediately with unfamiliar animals. Data from this project are just beginning to be published (Emery, Capitanio, Mason, Machado, Mendoza & Amaral, 2001; Prather, Lavenex, Mauldin, Mason, Capitanio, Mendoza & Amaral, 2001 ).