Personality method validation in common marmosets (Callithrix jacchus): Getting the best of both worlds.

Animal personality, consistent interindividual differences in behavior through time, has been intensively studied across animal taxa and particularly in nonhuman primates. Two different methods have been used to study personality: questionnaires filled out by trusted raters, following the research tradition in human personality psychology, and behavioral observations or testing, based on the behavioral ecology research tradition. Systematic research of cross-method validity has, however, brought equivocal results. Here we report a systematic method comparison with strict validation criteria in common marmosets (