- 2018年01月05日13:28 来源：互联网
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Animal behaviour——Planet of the apes
Chimpanzees' personas seem more complex than people's
HUMAN personalities, it is widely agreed by psychologists, can be measured along five dimensions: extroversion, agreeableness, conscientiousness, neuroticism and openness to experience.
One person may be more extrovert than another, less agreeable, more conscientious and so on, and to an extent how well two people will get on can be predicted from how their personalities mesh.
People who don't get on, though, have the option of avoiding each other.
That is not true of animals in zoos.
But they too have personalities.
So, to prevent trouble between members of one species—the chimpanzee—Hani Freeman of Lincoln Park Zoo, in Chicago, has developed a way of assessing those personalities.
In doing so, she sheds an intriguing light not only on chimpanzee psychology, but also on the mental evolution of Homo sapiens.
As they report in the American Journal of Primatology, Dr Freeman and her colleagues started by surveying the existing literature on chimpanzee behaviour.
This search threw up 55 terms, ranging from bold and jealous to stingy and sexual, that previous investigators had applied to aspects of chimpanzee character.
The team then asked five experts—a mixture of scientists and zookeepers, all of whom had had years of day-to-day experiences with captive chimpanzees—to provide their own lists of terms.
These inquiries collected 71 suggestions, 45 of which overlapped with the 55 from the literature search.
Finally, they compared their results with a review of chimpanzee behaviour carried out in 2008 by a different team. That comparison yielded two further terms.
Once Dr Freeman had gone through the accumulated list and merged into one term any set that seemed to mean the same thing, she was left with 41 that seemed robust descriptions of chimpanzee attitudes.
This done, she gave the list to 17 people who work with chimpanzees on a regular basis at a medical-research facility in Texas, and asked them to rate the 99 chimps there for each of the 41 characteristics.
She found that different people rated the same animals in the same way. That suggests their assessments were reliable.
She also found that scores for particular terms tended to cluster together.
A chimp that scored highly for irritability, for example, was also likely to score highly for aggression and for jealousy, and to have low scores for calmness and relaxation.
That let her apply a statistical technique called principal-component analysis to the data, to work out the dimensions of chimpanzee personality.
It is analysis of this sort which showed that human personas have five dimensions.
Chimps' personas, by contrast, seem to have six.
These are extroversion, agreeableness and openness, which match human dimensions, and reactivity, dominance and methodicalness, which do not.
Reactivity is similar to the human dimension called neuroticism, though not similar enough, in Dr Freeman's view, to justify the same label.
And methodicalness, which measures the way animals approach things like using tools and making the nests they sleep in, resembles conscientiousness—though Dr Freeman's raters found this difficult to assess because such activities are not much available to the chimps in Texas.
But there is, intriguingly, no human dimension that resembles chimpanzee dominance.
At the moment, it is possible to do little more than speculate about what all this means.
From a practical point of view it shows that it is probably not a good idea to put two animals with high dominance scores in the same enclosure—a discovery that addresses the question which started the research.
From a theoretical point of view it provides a way to study the mental similarities and differences between chimpanzees and humans:
what, in other words, is core anthropoid behaviour, and what is species-specific.