Personality in Nonhuman Animals: Comparative Perspectives and Applications

Personality in Nonhuman Animals: Comparative Perspectives and Applications

Until recently it was considered inappropriate for scientists to apply the construct of personality to nonhuman animals (see Loyer and Ha, 2017). Personality was sometimes considered to be an anthropomorphic term best ascribed only to those with personhood (Waters et al., 2017). Even when using less controversial terms, such as temperament, early researchers struggled to find acceptance for their pioneering work (see Whitham and Washburn, 2017 for a review of the history of the field). The tide has turned in recent decades, with a renewed enthusiasm for empirical approaches to studying animal welfare, along with a reluctant willingness to grant at least chimpanzees (Pan troglodytes) ‘personhood’ status (Tuttle, 2007). No longer taboo, the study of personality in nonhumans is seen as useful when applied to research topics such as conservation, animal welfare, and selection of service and companion animals. In addition, animals are now commonly used as models for human personality, including the study of personality and cognitive disorders (e.g., Khan and Echevarria, 2017). However, there is still much conjecture regarding the ideal approach to studying personality in nonhumans, including confusion over the use of terminology as well as arguments for and against different methodological approaches. In this chapter, we review some of the currently accepted practices and applications in this field, with an aim to convince the reader that the construct of personality is usefully applied to a better understanding of nonhuman as well as human behavior.

The renewed interest in and increasing breadth of the study of personality can be attributed in part to a shift in focus from normative trends to a growing fascination with individual differences within the field of psychology. Where psychologists once focused on finding group averages and discarding outliers, researchers now recognize that individual differences can be predictive in explaining human behaviors and attitudes. Individual differences have become such a popular topic of study that there are now [Page 24]several psychology journals devoted to this topic (e.g., Journal of Individual Differences, Personality and Individual Differences). Similarly, within the comparative literature, the traditional focus was on inter-species rather than intra-species differences. This oversight is somewhat surprising considering Darwin's (1859) early transformative discovery that individual variability was fundamental to the construct of hereditability, which serves as the foundation for natural selection. Natural selection is of course the key mechanism underlying the evolution of species. Thus, understanding intra-species variability is informative for understanding the evolution of particular traits, but is also critical to breeding programs and conservation initiatives, including reintroduction of species into wild habitats.

Also contributing to the broadening of this topic is an expansion of the species being studied by comparative psychologists in recent years. Where once psychologists would have barely ventured to consider personality types in chimpanzees – and disguised discussions of individuality in rats in behaviorist terms (e.g., Billingslea, 1941) – psychologists now regularly discuss behavioral syndromes and individual differences in species as diverse as zebrafish (Danio rerio; Khan and Echevarria, 2017), reptiles (Waters et al., 2017), domestic dogs (Canis lupus familiaris; Fratkin, 2017), cats (Felis catus; Gartner, 2017), rabbits (Oryctolagus cuniculus; Rödel and Monclús, 2011), marine mammals (Frick et al., 2017), and sharks (Finger et al., 2017). These changing trends are reflected in two recent volumes dedicated to the study of personality in nonhumans in general (Carere and Maestripieri, 2013; Vonk et al., 2017), and an earlier volume dedicated to personality in nonhuman primates in particular (Weiss et al., 2011). Behavioral ecologists have embraced the study of personality in the last decade as well, as reflected in several recent reviews (e.g., David and Dall, 2016; Dingemanse and Wolf, 2010; Réale et al., 2010a, 2007; Sih et al., 2004).

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