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Unseen, Monkeys Do; Seen, Monkeys Don't


21 March 2005
Copyright © 2005 Newsday. All rights reserved.

Off the coast of Puerto Rico, living in the wild, rhesus monkeys are teaching scientists a thing or two about reasoning and deception.

Given the opportunity to snag a grape, these primates do so only when they think no one is looking.

This, said Jonathan Flombaum of Yale University, suggests that monkeys are able to alter their behavior after making a judgment about what is going on in another's mind. This study shows monkeys can gather information from the environment that helps them make social decisions.

In the study, reported in the journal Current Biology, the monkeys focused on the scientists' eyes to see whether they were paying attention. Even when a scientist was facing them, if the scientist's eyes were averted, the monkeys took the grape, appearing to realize that the scientists were not looking.

Monkeys perceiving the scientist's gaze upon them understood that they were being watched and that it wasn't a good time to take the grape.

Flombaum, a graduate student, conducted the study in collaboration with Laurie Santos, an assistant professor in the department of psychology. The scientists hope that the finding might point the way to pathways involved in reasoning during social interactions and provide clues to human conditions where such social judgments are difficult, such as in autism. Many people with autism have difficulty reading people's eyes, which is how people tell what's on another person's mind.

The experiment was conducted on the island of Cayo Santiago. There, free-ranging colonies of monkeys live, and scientists work among them. In the current study, Flombaum and his colleagues walked around looking for an isolated monkey. They stood 15 feet away, placed a platform on the ground and attached a grape. As the scientists stood 4 feet apart facing the monkey, one scientist would avert his eyes (keeping his head straight) while the other would look at the monkey.

Over and over again, the monkeys would steal the grape from the experimenter who was not looking. In another experiment, they used cardboard to cover their mouths or their eyes. When the eyes were covered, the animals went after the grape, but not when the mouth was covered. "They can take the other's perspective," Flombaum said.

In a recent study, two grapes are placed on a ramp and the scientist, unknown to the monkey, releases one of the grapes. As it falls, it lands at the bottom, half the time sheltered by a canopy. Only when the canopy is present, and the monkey decides that the human doesn't see the fallen grape, will he go for the food.

Flombaum said that the autistic brain can't make these same judgments based on social cues.

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