CHICAGO Monkeys performed about as well as college students at mental addition, U.S. researchers said on Monday in a finding that suggests nonverbal math skills are not unique to humans.
The research from Duke University follows the finding by Japanese researchers earlier this month that young chimpanzees performed better than human adults at a memory game.
Prior studies have found non-human primates can match numbers of objects, compare numbers and choose the larger number of two sets of objects.
"This is the first study that looked at whether or not they could make explicit decisions that were based on mathematical types of calculations," said Jessica Cantlon, a cognitive neuroscience researcher at Duke, whose work appeared in the Public Library of Science journal PLoS Biology (www.plosbiology.org).
"It shows when you take language away from a human, they end up looking just like monkeys in terms of their performance," Cantlon said in a telephone interview.
Her study pitted the monkey math team of Boxer and Feinstein -- two female macaque monkeys named for U.S. senators Barbara Boxer and Dianne Feinstein of California -- with 14 Duke University students.
"We had them do math on the fly," Cantlon said.
The task was to mentally add two sets of dots that were briefly flashed on a computer screen. The teams were asked to pick the correct answer from two choices on a different screen.
The humans were not allowed to count or verbalize as they worked, and they were told to answer as quickly as possible. Both monkeys and humans typically answered within 1 second.
And both groups fared about the same.
Cantlon said the study was not designed to show up Duke University students. "I think of this more as using non-human primates as a tool for discovering where the sophisticated human mind comes from," she said.
The researchers said the findings shed light on the shared mathematical abilities in humans and non-human primates and shows the importance of language -- which allows for counting and more advanced calculations -- in the evolution of math in humans.
"I don't think language is the only thing that differentiates humans from non-human primates, but in terms of math tasks, it is probably the big one," she said.
As for the teams, both were paid. Boxer and Feinstein got their favorite reward: a sip of Kool-Aid soft drink. As for the students, they got $10 each -- enough for a beer or two.
(Editing by Sandra Maler)