Abstract
Personality has been linked to individual variation in interest and performance in cognitive tasks. Nevertheless, this relationship is still poorly understood and has rarely been considered in animal cognition research. Here, we investigated the association between personality and interest, motivation and task performance in 13 sanctuary chimpanzees (Pan troglodytes) housed at Fundació Mona (Spain). Personality was assessed with a 12-item questionnaire based on Eysenck’s Psychoticism-Extraversion-Neuroticism model completed by familiar keepers and researchers. Additionally, personality ratings were compared to behavioral observations conducted over an 11-year period. Experimental tasks consisted in several puzzle boxes that needed to be manipulated in order to obtain a food reward. Dependent variables included participation (as an indicator of interest), success and latency (as measures of performance), and losing contact with the task (as an indicator of motivation). As predicted, we obtained significant correlations between Eysenck’s personality traits and observed behaviors, although some expected associations were absent. We then analyzed data using Generalized Linear Mixed Models, running a model for each dependent variable. In both sexes, lower Extraversion and lower Dominance were linked to a higher probability of success, but this effect was stronger in females. Furthermore, higher Neuropsychoticism predicted higher probability of success in females, but not in males. The probability of losing contact with the task was higher in young chimpanzees, and in those rated lower on Extraversion and higher on Dominance. Additionally, chimpanzees rated higher on Neuropsychoticism were also more likely to stop interacting with the task, but again this was more evident in females. Participation and latency were not linked to any personality trait. Our findings show that the PEN may be a good model to describe chimpanzee personality, and stress the importance of considering personality when interpreting the results of cognitive research in non-human primates.
Highlights
Research on animal personality has been defined as behavioral inter-individual differences consistent over time and across contexts (Réale et al, 2007), and is a field of growing interest, both from a theoretical and an applied perspective
Since one of the most relevant attempts to describe chimpanzee personality using a human model with a hierarchical structure (King & Figueredo, 1997), several studies in captivity and in the wild have shown that chimpanzees have specific personality dimensions or traits that are common to their species (King, Weiss & Farmer, 2005; Weiss et al, 2012; Weiss et al, 2017), and that questionnaires adapted from human models are reliable measures of their personality (Freeman et al, 2013; Úbeda & Llorente, 2015; Weiss & Adams, 2013; Weiss et al, 2009; Weiss et al, 2017)
Extraversion was positively correlated with social behaviors; Neuropsychoticism was positively associated with total agonistic interactions; and Dominance positively correlated with agonistic dominance, and with total agonistic interactions
Summary
Research on animal personality has been defined as behavioral inter-individual differences consistent over time and across contexts (Réale et al, 2007), and is a field of growing interest, both from a theoretical and an applied perspective. Personality has been broadly studied in non-human primates (Freeman & Gosling, 2010; Weiss, King & Murray, 2011), since our closest living relatives constitute an excellent model for comparative research, providing insight on the evolutionary origins of human personality (Figueredo et al, 2015; Michalski & Shackelford, 2010). Most nonhuman primates exhibit complex social structures and behaviors, which likely favored the emergence of individual differences (Adams et al, 2015; Mitani et al, 2012). Their phylogenetic closeness to humans allows us to better understand and rate their personality traits using questionnaires (Weiss & Adams, 2013). Not all the expected traits associate with
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