Temporal consistency and ecological validity of personality structure in common marmosets (Callithrix jacchus): A unifying field and laboratory approach

Abstract

Personality in animals has been extensively researched in recent decades. Temporal consistency of behaviors is almost always part of the personality definition and is usually explored in several different testing sessions or observation periods. However, it is still unclear whether the obtained personality constructs are stable across several years, which might be especially important for long-living animals, such as primates. Further, little is known on whether the personality structures obtained in the laboratory reflect the structures obtained under ecologically relevant conditions in the wild. Therefore, we conducted a battery of personality tests on common marmosets (Callithrix jacchus) (N = 27), compared it with a test battery conducted 4 years beforehand on a subset of animals in captivity (N = 13) and ran an adapted version under field conditions at Baracuhy Biological Field Station, Brazil (N = 18). Under captive conditions, we found a remarkably similar personality structure across 4 testing years. Further, we found high long-term temporal consistency in the first two personality components, Boldness and Exploration; however, monkeys that changed their social (i.e., breeding) status between the two testing periods showed a significant increase in Boldness scores. Under field conditions, we found a somewhat similar personality structure as compared to the laboratory, which to some extent corroborates ecological validity of our personality test design. Nevertheless, whether the structure in the wild is suppressed or expanded in comparison to captivity, and in which way the social setting influences personality structure, should be further explored. Taken together, our results contribute to the discussion about the reliability and ecological validity of personality structures in nonhuman primates.

Personality, subjective well-being, and the serotonin 1a receptor gene in common marmosets (Callithrix jacchus)

“…The problems that affect human studies that purportedly find higher-order personality factors were absent in the present study: each animal was rated by two or three keepers, the correlations among latent variables were considerable, and adjusting for rater effects increased rather than decreased some interfactor correlations. Nevertheless, because second-order factors were not identified in other studies of common marmosets [ 13 , 17 , 31 , 44 ], including one that included 77 of the same animals, prior to interpreting the meaning of this phenomenon, we urge an attempt to replicate these findings and an analysis of similar data using more flexible modeling techniques [e.g., 11 ].…”

“…One reason for why a low level of between-subjects variance may come is that unmeasured influences, for example how animals are housed or bred, overwhelms, or makes it difficult to observe or perceive, individual differences in one or more traits. Recent findings that appear to rule out this possibility come from a study that found the same structure in laboratory-housed and wild common marmosets [ 44 ]. However, because the captive and wild groups lived in family groups, that study could not exclude the possibility that being raised in other kinds of groups might affect personality structure.…”

Personality, Subjective Well-Being, and the Serotonin 1a Receptor Gene in Common Marmosets (Callithrix jacchus)

“…The problems that affect human studies that purportedly find higher-order personality factors were absent in the present study: each animal was rated by two or three keepers, the correlations among the latent variables were considerable, and adjusting for rater effects increased rather than decreased some correlations among factors. Nevertheless, because second-order factors were not identified in other studies of common marmosets [13, 17, 31, 44], including one that included 77 of the same animals, prior to interpreting the meaning of this phenomenon, we urge an attempt to replicate these findings and an analysis of similar data using more flexible modeling techniques [e.g., 11].…”

“…A low level of between-subjects variance may come about when unmeasured influences, for example in how animals are housed or bred, overwhelm or make it difficult to observe or perceive individual differences in one or more traits. However, a study that compared common marmosets that lived in a laboratory to those that lived in the wild [44] suggests that this does not happen. A low level of between-subjects variance may also come about because the personalities of individuals conform to that of their group [12].…”

“…A low level of between-subjects variance may come about when unmeasured influences, for example how animals are housed or bred, overwhelms, or makes it difficult to observe or perceive, individual differences in one or more traits. Recent findings that appear to rule out this possibility come from a study that found the same structure in laboratory- housed and wild common marmosets [44]. However, because the captive and wild groups lived in family groups, that study could not exclude the possibility that being raised in other kinds of groups might affect personality structure.…”