Do chimpanzees, orangutans and other nonhuman great apes have distinct personalities like us? It’s been a longstanding debate within the scientific community, and those who seek to exploit these animals have long argued that “personality” is a distinctly human attribute, not shared by any other species.
Of course, anyone with a dog or cat at home knows perfectly well that every pet they’ve ever known had a distinct personality. And anyone who’s worked with chimps and other great apes in the wild, in a zoo or in a laboratory setting has seen the wide variety of their personalities.
The denialists, however, have generally countered this by arguing that any such perceived behavior is nothing more than an anthropomorphic projection of the human observers onto the animals they’re observing.
Now an independent study addresses the denialist argument and concludes that, yes, these great apes do indeed have their own personalities.
Using a statistical method that was designed to remove any biases in human observers, researchers at the University of Edinburgh said their study suggests humans and apes really do share “personality dimensions.”
“[Chimpanzees] have the same social problems that we do,” said Mark Adams, a doctoral student who conducted the research. “They want to make friends and find mates and sort of gain position within their society,”
Alexander Weiss, a senior lecturer at the university who was also part of the study, agreed that chimpanzee personality is “highly similar” to that of humans, probably due to genetic similarities. (Humans and chimps diverged from a common ancestor only 4 to 6 million years ago.)
For the purposes of the study, researchers used one of the standard tests that psychologists use to categorize human personality – by seeing measuring personality in five dimensions: one’s degree of a) openness to experience, b) conscientiousness, c) extroversion, d) agreeableness, and e) neuroticism (OCEAN).
Previous studies suggested that chimpanzees share these five dimensions with humans, while orangutans display three of the five: extroversion, neuroticism and agreeableness.
Chimpanzee personality is ‘highly similar’ to that of humans, probably due to genetic similarities.
Following up on this, and with a view to eliminating the possibility of observers projecting their own ideas about personality onto these animals, members of the research team issued questionnaires to around 230 people observing chimpanzees and orangutans in zoos and research centers in the US, Canada, Australia and Japan. (Team members from Kyoto University in Japan and the University of Arizona, as well as University of Edinburgh.)
The survey described 40 to 50 personality “items”, which, when grouped together, make personality dimensions.
The observers were asked to rate the apes’ behavior on a one-to-seven point scale for each personality item. And from the questionnaire results, the team determined any kinds of bias present in the observations of the animals.
“We used a statistical technique to remove these observer differences before extracting personality traits from the data,” Mark Adams told the BBC. “What we found was that controlling for these differences among observers made no difference, which suggests that the observers are not projecting their own ideas about personality onto the animals.”
Dr. Weiss said that the research “vindicates both the view that chimpanzees have personalities and perhaps the more controversial statement that their personalities are quite similar to those of humans.”
The study, published online in the journal Animal Behavior, concluded that the apes who were observed have a range of individual character traits such as being affectionate, sympathetic, jealous and manipulative.
The study also showed that orangutans are not, as previously thought, limited to three of the five dimensions, but also showed clear evidence of conscientiousness and openness to experience.
“It’s an interesting development,” said Dr. Weiss, “as until now, conscientiousness, which includes being careful and organized, had only been identified in chimps and humans … When we look at the personalities of chimpanzees and orangutans, we find strong similarities to human personality traits in the way that personality traits group into personality domains.”
He said that the study presented clear evidence that these animals have their own unique personalities.
“It’s the toughest test yet of this view, a high risk test, but the results ultimately supported the hypothesis that personality ratings are not overly tainted by human biases.”