While psychologists have long debated the core personality
dimensions that define humanity, primate researchers have been working to
uncover the defining personality traits for humankind's closest living
relative, the chimpanzee.
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.
"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
How the research was
The study of chimpanzee personality is not novel; however,
according to the authors, previous instruments designed to measure personality
left a number of vital questions unanswered.
"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," explained
"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."
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
This new scale consisted of 41 behavioural descriptors
including boldness, jealousy, friendliness and stinginess amongst 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, UT 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
To validate their findings, the researchers used two years
worth of behavioural data collected on the chimpanzees. As the authors expected,
the findings showed the personality ratings were associated with differences in
how the chimpanzees behaved. The researchers also showed the raters tended to
agree in their independent judgements of chimpanzees' personalities, suggesting
the raters were not merely projecting traits onto the chimpanzees.
Researchers suggest that one benefit to having the
chimpanzees rated on the five core personality dimensions is that this
information can now be used to make predictions that will help in their
management, such as how individual chimpanzees will behave in various social
situations. This type of information will help zoos better anticipate certain behaviours
from various individuals, and will assist them in providing individualized