Personality structure and social style in macaques.
Résumé
Why regularities in personality can be described with particular dimensions is a basic
question in differential psychology. Nonhuman primates can also be characterized in terms of
personality structure. Comparative approaches can help reveal phylogenetic constraints and
social and ecological patterns associated with the presence or absence of specific personality
dimensions. We sought to determine how different personality structures are related to
interspecific variation in social style. Specifically, we examined this question in six different
species of macaques, as macaque social style is well characterized and can be categorized on
a spectrum of despotic (grade 1) versus tolerant (grade 4) social styles. We derived
personality structures from adjectival ratings of Japanese (Macaca fuscata; grade 1),
Assamese (M. assamensis; grade 2), Barbary (M. sylvanus; grade 3), Tonkean (M. tonkeana;
grade 4), and crested (M. nigra; grade 4) macaques and compared these species to rhesus
macaques (M. mulatta; grade 1) whose personality has previously been characterized. Using a
non-parametric method, fuzzy set analysis, to identify commonalities in personality
dimensions across species, we found that all but one species exhibited consistently defined
Friendliness and Openness dimensions, but that similarities in personality dimensions
capturing aggression and social competence reflect similarities in social styles. These
findings suggest that social and phylogenetic relationships contribute to the origin,
maintenance, and diversification of personality.