Rhesus Macaques (Macaca mulatta) as Living Fossils of HominoidPersonality and Subjective Well-BeingAlexander Weiss and Mark James AdamsUniversity of EdinburghAnja WiddigMax Planck Institute for Evolutionary Anthropology,and University of LeipzigMelissa S. GeraldUniversity of Puerto Rico—Medical Sciences CampusPersonality dimensions capturing individual differences in behavior, cognition, and affect have been describedin several species, including humans, chimpanzees, and orangutans. However, comparisons between speciesare limited by the use of different questionnaires. We asked raters to assess free-ranging rhesus macaques attwo time points on personality and subjective well-being questionnaires used earlier to rate chimpanzees andorangutans. Principal-components analysis yielded domains we labeled Confidence, Friendliness, Dominance,Anxiety, Openness, and Activity. The presence of Openness in rhesus macaques suggests it is an ancestralcharacteristic. The absence of Conscientiousness suggests it is a derived characteristic in African apes. HigherConfidence and Friendliness, and lower Anxiety were prospectively related to subjective well-being, indicat-ing that the connection between personality and subjective well-being in humans, chimpanzees, and orang-utans is ancestral in catarrhine primates. As demonstrated here, each additional species studied adds anotherfold to the rich, historical story of primate personality evolution.Keywords: rhesus macaque, primate, personality, stability, well-beingNonhuman primate personality traits capture impressions thatare reliable in that they are consistent across raters and time (King& Figueredo, 1997; King, Weiss, & Sisco, 2008; Stevenson-Hinde,Stillwell-Barnes, & Zunz, 1980; Uher, Asendorpf, & Call, 2008;Weiss, King, & Perkins, 2006). Nonhuman primate personalitytraits are also valid in that they are related to other measures,including observed behavior (Capitanio, 1999; Konecˇna´ et al.,2008; Pederson, King, & Landau, 2005; Stevenson-Hinde et al.,1980; Uher & Asendorpf, 2008).Like the study of physical characteristics in different species, thecomparative method can address questions concerning the evolu-tion of stable personality traits (Gosling & Graybeal, 2007; Harvey& Pagel, 1991). King and Figueredo (1997) examined personalityphylogeny by obtaining ratings of zoo chimpanzees on a question-naire based on measures of the five major dimensions along whichhumans differ — Neuroticism, Extraversion, Openness, Agree-ableness, and Conscientiousness (Digman, 1990). They found abroad chimpanzee-specific Dominance domain, and five additionaldomains that, while differing slightly on the trait level, wereanalogous to human personality domains (King & Figueredo,1997). Thus, precursors of human personality were likely presentin the common chimpanzee-human ancestor and early hominids,though dominance was no longer a key domain upon whichmembers of the latter could be distinguished. A study of orangutanAlexander Weiss and Mark James Adams, Department of Psychology,School of Philosophy, Psychology and Language Sciences, University ofEdinburgh; Anja Widdig, Junior Research Group of Primate KinSelection, Department of Primatology, Max Planck Institute for EvolutionaryAnthropology, and Institute of Biology, University of Leipzig; and Melissa S.Gerald, Caribbean Primate Research Center and Department of Internal Med-icine, University of Puerto Rico—Medical Sciences Campus.Melissa S. Gerald is now at the Center for Scientific Review, NationalInstitutes of Health. Melissa S. Gerald contributed to this article as anemployee of the University of Puerto Rico—Medical Sciences Campus.This study complies with the current laws of Puerto Rico and the UnitedStates. The IACUC of the University of Puerto Rico, Medical SciencesCampus approved this investigation. The rhesus macaque population ofCayo Santiago is supported by the University of Puerto Rico, MedicalSciences Campus and by the National Center for Research Resources(NCRR), a component of the National Institutes of Health (NIH) (NCRRGrant P40RR003640 Award to the CPRC). The content of this publicationis solely the responsibility of all of the authors and does not necessarilyrepresent the official views of NCRR, NIH, or the United States Govern-ment. We thank Amanda K. Accamando, Lauren J. N. Brent, Julie Cascio,Camille Guillier, Doreen Hess, Constance Dubuc, Veronique Martel, Jen-nifer L. Danzy, Joyce Moewius, Maggie Chivavetta, Veronica Gutierrez,Claude Richer, Agnieszka Sukiennik Koniec, and Akie Yanagi for ratingthe monkeys. Without their cooperation, this project would not have beenpossible. We also thank Edgar Davı´la and Julio Resto for maintaining adaily census of the rhesus macaques of Cayo Santiago. We thank Jana Uherand Michael Tomasello for their helpful comments on a draft. Finally, wewould like to thank one anonymous reviewer for suggesting the analysesdepicted in Table 3 and both anonymous reviewers for several helpfulcomments which have improved the manuscript.Correspondence concerning this article should be addressed to Alexan-der Weiss, Department of Psychology, School of Philosophy, Psychologyand Language Sciences, University of Edinburgh, 7 George Square, Edin-burgh EH8 9JZ, United Kingdom. E-mail: [email protected] of Comparative Psychology © 2011 American Psychological Association2011, Vol. 125, No. 1, 72– 83 0735-7036/11/$12.00 DOI: 10.1037/a002118772personality using an expanded version of the same questionnaire asthat used to rate chimpanzees found variants of human and chim-panzee Neuroticism, Extraversion, and Agreeableness domains aswell as a Dominance domain, suggesting that these domains mayhave existed in the common ancestors of great apes and humans(Weiss et al., 2006). In addition, this same study found that, insteadof making up separate domains, traits defining Openness andConscientiousness defined a single domain in orangutans namedIntellect, suggesting that selection may have favored separateOpenness and Conscientiousness domains in species such as hu-mans and chimpanzees, which have more complex social struc-tures.Although personality differences have been described in greatapes and humans, the historical patterns of personality evolutioncannot be deduced from examining this taxon alone. Studyingpersonality in Old World monkeys, which split off from hominoidsbetween 25 and 30 mya (Andrews, 1986), could offer insights intothe evolutionary origins of