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Chimps won’t do a neighbor a favor
Oct. 26, 2005
Special to World Science
Long ago were the days, it seems, when we humans could consider ourselves truly
unique.
With chimps and other animals having been found to exhibit a range of human-like traits—including tool use,
culture and
some elements of language—it’s gotten harder and harder for scientists and philosophers to say
just what sets us apart.
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They just don't care that much, a new study
suggests. (Image courtesy National Institutes of Health)
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Finally, there may be some news to make us feel special again.
Researchers say they may have found one key trait that clearly separates humans from chimps, and possibly
from other species: we’re the only ones that do favors without expecting something in return.
Chimps don’t show this sort of consideration, the researchers found.
To be sure, they have been found to exhibit signs of empathy. Chimps help family members, for example, and sometimes console victims of aggression. But outside of these special situations, according to the scientists, chimps will let neighbors cast for themselves.
Joan Silk of the University of California, Los Angeles and colleagues conducted a study that they said confirmed this, showing chimps are uninterested
in doing a friend a good turn, even at no cost to themselves.
The researchers presented captive chimps with a device that gave them a choice between two options. The
chimp could choose to serve only itself with food, or it could select an option that gave it the same food, but also resulted in food being delivered to another chimpanzee.
The chimpanzees were no more likely to choose the second option, even though they could see that it would help a friend at no
inconvenience to themselves, the researchers said.
Many human habits—such as donating blood, giving to charity and punishing social offenders—show consideration for others, even strangers. The chimpanzees’ lack of
such regard was made more surprising by the fact that the chimpanzees used in the study had been living together in stable social groups for many years, the researchers said.
The scientists added that they conducted the test with two separate chimp populations, and got the same results.
“Chimpanzees cooperate mainly with kin and reciprocating partners,” they wrote in a paper to appear in the Oct. 27 issue of the research journal
Nature.
Chimps have also been found to have a sense of “fairness,” in that they respond negatively to unfair
interactions. But they do so only when they themselves get the raw deal, not someone else. They “show no aversion to inequitable exchanges that benefit themselves,” Silk and colleagues wrote.
“The absence of other-regarding preferences in chimpanzees,” they added, “may indicate that such preferences are a derived property of the human species”—that
is, a trait we developed independently of our evolutionary ancestors.
This trait may be “tied to sophisticated capacities for cultural learning, theory of mind [the ability to infer someone else’s thoughts], perspective taking and moral judgement,” the authors added.
Nonetheless, it’s possible that some other animals will turn out to do favors after all, the researchers said.
“Other-regarding preferences might be found in other species that rely more heavily on cooperative strategies than chimpanzees do, such as cooperatively breeding mammals. Further work on other species will help to clarify the socioecological conditions and cognitive requirements associated with the evolution of other-regarding preferences.”
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