Abstract
Personality factors analogous to the Big Five observed in humans are present in the great apes. However, few studies have examined the long-term stability of great ape personality, particularly using factor-based personality instruments. Here, we assessed overall group, and individual-level, stability of chimpanzee personality by collecting ratings for chimpanzees (N = 50) and comparing them with ratings collected approximately 10 years previously, using the same personality scale. The overall mean scores of three of the six factors differed across the two time points. Sex differences in personality were also observed, with overall sex differences found for three traits, and males and females showing different trajectories for two further traits over the 10 year period. Regardless of sex, rank-order stability analysis revealed strong stability for dominance; individuals who were dominant at the first time point were also dominant 10 years later. The other personality factors exhibited poor to moderate rank-order stability, indicating that individuals were variable in their rank-position consistency over time. As many studies assessing chimpanzee cognition rely on personality data collected several years prior to testing, these data highlight the importance of collecting current personality data when correlating them with cognitive performance.
Highlights
The turn of the twenty-first century saw an unprecedented interest in non-human animal personality
To examine sex differences in personality, we looked at main effects of sex, time by sex interactions and where appropriate, within-sex effects for each factor
Stability of chimpanzees’ personality over time; overall and sex differences We examined the stability of multiple chimpanzee personality traits by measuring changes in factors across an approximately 10 year period using the same instrument, revealing consistencies and differences with previous work
Summary
The turn of the twenty-first century saw an unprecedented interest in non-human animal (hereafter animal) personality. Numerous animal species are known to display consistent individual variation in behaviour across time and contexts. This individual variation is known to have a wide-ranging impact onanimals, including on measures of fitness and welfare (Dall et al, 2004; Dingemanse & Wolf, 2010; Gosling, 2001; McCowan et al, 2014) and cognition (Lermite et al, 2016). Understanding animal personality augments our knowledge of the origins of human personality, and comparative studies of personality help us understand development in human personality by providing non-human-centric perspectives (Weiss et al, 2012). Chimpanzees’ phylogenetic proximity to humans makes them a valuable
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