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Experiment Reveals Monkeys Able to Count at Least to Nine

By Rick Weiss
The Washington Post

Monkeys have an innate ability to conceptualize numbers and can be taught to count at least to the number nine, according to a series of groundbreaking experiments that promise new insights into the evolution of intelligence.

The research, in which monkeys played math-based video games, challenges a longstanding view among many scientists that humans are unique in their ability to grasp the concepts of number, numerical order and basic arithmetic.

It stops short of concluding that monkeys can add or subtract. But it indicates they can grasp the relatively sophisticated concepts of "twoness," "threeness" and so on, and can comprehend how those concepts relate to each other about as well as a human 3-year-old can.

Experts hailed the work as a major milestone in understanding the intellectual ability of animals.

"When I heard about these experiments, I thought, Wow, these are the neatest animal representation experiments of the decade,' " said Susan Carey, a cognitive scientist at New York University. "It is very clever and convincing work."

Previous experiments had offered hints of number awareness in non-human species, but some researchers suspected that those animals had inadvertently been trained to give rote replies or were just recognizing certain visual patterns, the way a person can recognize the pattern of dots on a domino without actually counting them. The new work is the first to indicate that animals can solve novel numerical problems through an apparently genuine understanding that some numbers are bigger or smaller than others.

The research may lead to the development of better methods for teaching basic counting skills to cognitively impaired people, researchers said. But it is primarily important to psychologists, philosophers and theologians, who have long debated the extent to which people and animals fundamentally differ - and especially the extent to which animals can think.

"Mathematical thinking is considered to be one of the most important and complicated abilities that humans have, along with language," said Elizabeth M. Brannon, the Columbia University graduate student who conducted the monkey experiments.

In the new experiments, a pair of 2-year-old monkeys named Rosencrantz and Macduff sat before touch-sensitive computer monitors that displayed four square "windowpanes." One pane always contained a single item, such as a car; another pane contained a pair of items, such as two apples; the third pane contained three identical items; and the fourth contained four items. In a series of 35 trials in which the types, colors, sizes and relative locations of the one-, two-, three-, and four-item panes varied, the monkeys were trained to touch the one-item pane first, then the two-item pane, then the three and finally the four.