Personality in nonhuman primates: a review and evaluation of past research

Abstract

Scientific reports of personality in nonhuman primates are now appearing with increasing frequency across a wide range of disciplines, including psychology, anthropology, endocrinology, and zoo management. To identify general patterns of research and summarize the major findings to date, we present a comprehensive review of the literature, allowing us to pinpoint the major gaps in knowledge and determine what research challenges lay ahead. An exhaustive search of five scientific databases identified 210 relevant research reports. These articles began to appear in the 1930s, but it was not until the 1980s that research on primate personality began to gather pace, with more than 100 articles published in the last decade. Our analyses of the literature indicate that some domains (e.g., sex, age, rearing conditions) are more evenly represented in the literature than are others (e.g., species, research location). Studies examining personality structure (e.g., with factor analysis) have identified personality dimensions that can be divided into 14 broad categories, with Sociability, Confidence/Aggression, and Fearfulness receiving the most research attention. Analyses of the findings pertaining to inter-rater agreement, internal consistency, test-retest reliability, generally support not only the reliability of primate personality ratings scales but also point to the need for more psychometric studies and greater consistency in how the analyses are reported. When measured at the level of broad dimensions, Extraversion and Dominance generally demonstrated the highest levels of inter-rater reliability, with weaker findings for the dimensions of Agreeableness, Emotionality, and Conscientiousness. Few studies provided data with regard to convergent and discriminant validity; Excitability and Dominance demonstrated the strongest validity coefficients when validated against relevant behavioral criterion measures. Overall, the validity data present a somewhat mixed picture, suggesting that high levels of validity are attainable, but by no means guaranteed. Discussion focuses on delineating major theoretical and empirical questions facing research and practice in primate personality.

Common marmoset (Callithrix jacchus) personality.

“…This finding lends further support to the notion that domains like dominance, confidence, or assertiveness are universal features of personality in nonhuman primates (see, e.g., Freeman & Gosling, 2010).…”

“…This component was thus similar to the extraversion domain found in the previous study of marmosets (Iwanicki & Lehmann, 2015) and domains labeled dominance, confidence, and assertiveness in other nonhuman primate species (Freeman & Gosling, 2010). We thus named this component 'assertiveness'.…”

Personality structure and social style in macaques.

“…Phylogenetic analysis is highly informative of function in social and personality psychology because it can reveal the evolutionary history of the co-occurrence of behaviors (Fraley, Brumbaugh, & Marks, 2005;Gosling & Graybeal, 2007). Analogues of the five factors, along with the dimensions Dominance and Activity, have been found in nonhuman primates, although species differ in the personality dimensions they exhibit (Freeman & Gosling, 2010). Within at least one nonhuman primate species, i.e., chimpanzees, personality structures derived from rater assessments are relatively invariant across habitats, rearing environments, social groups, and observers' cultures (Pederson, King, & Landau, 2005;Weiss, King, & Hopkins, 2007); and chimpanzee personality dimensions differ from those exhibited by other primate species (Morton et al, 2013;.…”

Variation in personality and fitness in wild female baboons

“…Indeed, most studies of personality in nonhuman primates have relied wholly or in part on assessments by human observers and seldom considered the function of the resulting "trait" classifications (e.g., refs. [17][18][19][20][21]. In contrast, we began with the behavior of the animals themselves and considered whether any functionally interesting personality dimensions emerged from these data.…”