The influence of rearing on personality ratings of captive chimpanzees (Pan troglodytes)

Personality traits of 43 captive chimpanzees (Pan troglodytes) at five zoos in the United Kingdom were assessed. Chimpanzees were categorised into one of three rearing conditions: mother-group-reared (MGR), reared with others but separated from mother (RO), and reared alone for a period of time during infancy (RA). This study was interested in the effects of early upbringing on the personality traits observed in later life. Individuals were rated for 25 adjectives. Inter-rater reliability was found to be affected by the rearing condition of the chimpanzee being rated, with MGR chimpanzees being easier to rate reliably than their non-MGR peers. Individual traits were compared between individuals from different rearing conditions. No differences in trait could be found that could be related to rearing condition. Although five personality components were identified by principal component analysis there was no difference in individuals' scores for these animals from different rearing conditions. Cluster analysis revealed three distinct chimpanzee personality types: an aggressive male type, a confident, intelligent female type and a deferent, apprehensive female type. It was concluded that in many socially separated individuals personality in later life was unaffected by experiences in infancy, however, maternally separated individuals were distinguishable by a low-rater reliability. This supported earlier work that assessed behavioural differences between these different rearing groups. Both behaviour and personality show limited affects of upbringing-type once chimpanzees are passed juvenility.