Atypical early life histories predict lower extraversion in captive chimpanzees

There are still gaps in our understanding of personality development in humans, particularly in relation to social influences. Chimpanzee personality development may provide useful insight. We evaluated the impact of early life experiences on personality development by studying 88 chimpanzees living in accredited zoos and sanctuaries. During infancy, subjects varied in the amount of time spent with conspecifics compared with humans. Caregivers familiar with the chimpanzees rated them using a modified version of the Hominoid Personality Questionnaire (HPQ). The ratings were found to have strong inter-rater reliability. We used the six-factor structure of the HPQ to evaluate our results in relation to differences in early life experience. Chimpanzees who as infants were less exposed to conspecifics were rated as lower in Extraversion later in life. These results suggest that a broader range of social influences should be considered when evaluating the impact of early social environment on later personality expression.