In fact, college students used as controls in the study had the same success rate as the macaques—each group choosing the correct answer in as little as a second, Cantlon said at an American Association for the Advancement of Science meeting in Chicago.
Such similarities "suggest that these abilities are part of a primitive system for reasoning about numbers that has been passed down for millions of years of evolutionary time," she said.
Though previous studies have shown a limited capability for subtraction among nonhuman animals, the new data are "the first evidence of widespread success," Cantlon said by email.
Past experiments by other researchers, for example, used only small numbers, she said. Previous studies also did not vary the dot sizes in the multiple choice section, so the larger number always looked physically bigger—possibly tipping off the animals to which set of dots represented the larger sum.
A 2007 study co-authored by Cantlon proved monkeys' success with addition—again on par with college students performing the same tasks.
Animals' knack for numbers can boost survival in the wild, Cantlon told National Geographic News.
For instance, research has shown that apes can determine at a glance roughly how much food is present in an area and decide whether to stay and eat or to move on, she said.
On the 200th anniversary of Charles Darwin's birth, "these studies suggest we humans should keep our egos in check," said Edward Wasserman, an experimental psychologist at the University of Iowa.
"We are certainly not the only intelligent animals on Earth."
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