Measuring personality in the field: An in situ comparison of personality quantification methods in wild Barbary macaques (Macaca sylvanus).

Abstract

Three popular approaches exist for quantifying personality in animals: behavioral coding in unconstrained and experimental settings and trait assessment. Both behavioral coding in an unconstrained setting and trait assessment aim to identify an overview of personality structure by reducing the behavioral repertoire of a species into broad personality dimensions, whereas experimental assays quantify personality as reactive tendencies to particular stimuli. Criticisms of these methods include that they generate personality dimensions with low levels of cross-study or cross-species comparability (behavioral coding in unconstrained and experimental settings) or that the personality dimensions generated are not ecologically valid, that is, not reflecting naturally occurring behavior (trait assessment and experimental assays). Which method is best for comparative research is currently debated, and there is presently a paucity of personality research conducted in wild subjects. In our study, all three described methods are used to quantify personality in a wild animal subject, the Barbary macaque (Macaca sylvanus). Our results show that the structures generated by unconstrained behavioral coding and trait assessment were not equivalent. Personality dimensions derived from both trait assessments and experimental assays demonstrated low levels of ecological validity, with very limited correlation with behaviors observed in nonmanipulated circumstances. Our results reflect the methodological differences between these quantification methods. Based on these findings and the practical considerations of wild animal research, we suggest future comparative studies of quantification methods within similar methodological frameworks to best identify methods viable for future comparisons of personality structures in wild animals.

Long-term repeatability in social behaviours suggests stable social phenotypes in wild chimpanzees

“…Our study expands on former research in this field in terms of its scale, both temporally and in the range of behaviours examined, in a wild population, demonstrating that social phenotypes are a phenomenon in long-lived species occupying complex social environments. Indeed, given the results of our study and work conducted in taxa ranging from insects (23) to fish (24,25) to birds (19) to primates (20,89), consistent individual differences in social phenotypes seem the norm for group-living animals regardless of the degree of social complexity.…”

“…Importantly, we found consistent individual differences in multiple forms of social interaction. Much research to date on social phenotypes has focused solely on association patterns (19,25), or on single forms of dyadic interaction (20, 34), with a minority of studies examining consistency in multiple forms of social behaviours (89,98,99). Our study shows that consistent individual differences in social behaviour extends to patterns of aggression and affiliation, both of which should influence fitness more than association alone (43,44,85–88,100).…”

Personality homophily affects male social bonding in wild Assamese macaques (Macaca assamensis)

“…Further, in a trait rating study with juvenile rhesus macaques, an equitability dimension (e.g., calmer, more easygoing, less active), which also includes aspects of social tolerance, correlated with relationship stability (Weinstein & Capitanio, 2012). However, in a social network study with wild Barbary macaques, it was not similarity in social tolerance but excitability (contains elements related to low impulse control: excitable, impulsive, erratic and disorganized) that was correlated with spatial association (Tkaczynski, 2017), albeit this effect was not seen in grooming networks.…”

“…Here we investigated whether patterns of affiliation correspond to homophily in personality traits in wild male Assamese macaques. Apart from an unpublished PhD thesis (Tkaczynski, 2017) these studies all used captive animals and assessed personality either with behavioural or with trait rating (i.e. questionnaire) data.…”

Regularized Exploratory Bifactor Analysis With Small Sample Sizes

“…Recently, Jung and Takane (2008) have developed REFA via incorporating regularization methods into the common factor model. REFA has been widely used particularly in the comparative psychology literature (e.g., Tkaczynski et al, 2019). The current study expanded the literature by incorporating the idea of regularization into the bifactor model.…”