Personality features in vervet monkeys: The effects of sex, age, social status, and group composition.

Personality ratings were completed in 97 socially living vervet monkeys (Cercopithecus aethiops sabaeus) ranging in age from 19 months to 14 years. Monkeys were rated on 17 distinct items on three separate occasions over a 14 month period. For each rating session, factor analysis resulted in similar factors: socially competent, playful/curious, and opportunistic, which are provisionally labeled as personality features. Individuals' scores on the three factors were linked to the subjects' social status, age, and sex. Relative to subordinate animals, dominant individuals had higher scores on the socially competent and lower scores on the opportunistic factors. Juvenile and subadult animals scored higher on playful/curious and opportunistic factors than adults. Females had higher scores on the opportunistic factor than males. Scores on the three factors changed during maturation, which suggests that some aspects of personality are age- and context-dependent. When group composition and social status were unaltered, intraindividual differences in factor scores were as consistent over time as were the rates of social grooming, being in proximity to others, resting, and other overt behaviors. Alterations in social status, group composition, and group membership were associated with changes in factor scores among some, but not all animals. These observations suggest that studies assessing personality can supplement ethological investigations of nonhuman primate behavior, and support the view that nonhuman Primates can serve as models for important features of human behavior. © 1994 Wiley-Liss, Inc.