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Human assumptions that chimpanzees likely share watered-down versions of the human mind has clouded our interpretation of chimpanzee behavior, according to Daniel Povinelli, PhD, who presented "Chimpanzees, children and the evolution of the human capacity for explanation" at APA's 2001 Annual Convention.

Researchers have relied too much on the idea that because chimpanzees and humans evolved from a common ancestor, any trait in humans must have a comparable trait in chimpanzees. Though that might be true for some traits, it's not true for them all, he said.

In particular, he believes, it's not true for "theory of mind"--the human ability to understand the world from others' perspectives, which comparative psychologists have long tried to pin on chimpanzees.

"I'm making a plea for accepting the idea of diversity among minds out there in the world," said Povinelli, of the University of Southwestern Louisiana. If researchers can do that, he added, they'd have a much easier time deciphering research on chimpanzee behavior.

To persuade his audience, he summarized several years of research from his lab looking at how chimpanzees reason about social behavior and physical objects. It demonstrates, he said, that instead of using an understanding of others' beliefs and intentions to figure out social situations, chimps use more concrete cues such as others' posture and gaze. For example, they are just as likely to reach out for food to a person who isn't looking at them as to someone who is looking at them, but won't reach out to someone with his or her back turned.

"They are extremely sensitive to face and eyes, but they don't imbue them with the psychology of seeing," said Povinelli.

In some ways, chimpanzees see the world a lot more realistically than humans do, he said. Their view of the world isn't muddied by the complex reasoning humans do trying to figure out the world.

"Although chimpanzees and humans possess powerful psychological systems for extracting out statistical similarities in the world," said Povinelli, "humans alone appear to have evolved a system for explaining those statistical regularities in terms of unobservable events such as mental states and physical forces."

Beth Azar is a writer in Portland, Ore.