Scientists have uncovered five defining personality traits - dominance, openness, reactivity/undependability, extraversion and agreeableness - for humankind's closest living relative, the chimpanzee.
While psychologists have long debated the core personality dimensions that define humanity, primate researchers have been working to uncover the defining personality traits of the chimpanzee.
The new research published in the American Journal of Primatology provides strong support for the universal existence of five personality dimensions in chimpanzees: reactivity/undependability, dominance, openness, extraversion and agreeableness with a possible sixth factor, methodical, needing further investigation.
"Understanding chimpanzee personality has important theoretical and practical implications," explained lead author Hani Freeman, postdoctoral fellow with the Lester E Fisher Center for the Study and Conservation of Apes at Lincoln Park Zoo in Chicago.
"From an academic standpoint, the findings can inform investigations into the evolution of personality. From a practical standpoint, caretakers of chimpanzees living in zoos or elsewhere can now tailor individualised care based on each animal's personality thereby improving animal welfare.
"Some personality scales used for chimpanzees were originally designed for another species. These 'top-down' approaches are susceptible to including traits that are not relevant for chimps, or fail to include all the relevant aspects of chimpanzee personality.
"Another tactic, called a 'bottom-up' approach, derives traits specifically for chimpanzees without taking into account information from previous scales.
"This approach also has limitations as it impedes comparisons with findings in other studies and other species, which is essential if you want to use research on chimpanzees to better understand the evolution of human personality traits," explained Freeman.
To address the limitations of each approach and gain a better understanding of chimpanzee personality, the authors developed a new personality rating scale that incorporated the strengths of both types of scales.
This new scale consisted of 41 behavioural descriptors including boldness, jealousy, friendliness and stinginess among others.
Seventeen raters who work closely and directly with chimpanzees used the scale to assess 99 chimpanzees in their care at the Michale E Keeling Center for Comparative Medicine and Research, University of Texas MD Anderson Cancer Center in Bastrop.
The chimpanzees rated were aged 8 to 48, a majority had been captive born and mother-raised, and all had lived at the facility for at least two years.
