Thinking about thinking, that quintessentially human state of self-awareness, may not be such a uniquely human trait after all. J. David Smith of the State University of New York at Buffalo and his colleagues find that monkeys can ponder a problem, evaluate their own level of understanding, and then decide whether or not they know how to find the correct answer.
Smith’s team trained two 9-year-old rhesus monkeys to play a video game in which the animals were shown a series of images followed by a single one. They then had to decide if they had seen the single image before. The monkeys were allowed three responses—“there,” “not there,” and “don’t know”—for a food reward. When people perform similar memory tasks, they tend to respond “there” for the first and last images but opt for “don’t know” for those that appear in between, images they realize are more difficult to recall. Smith’s monkeys behaved exactly the same way. “These animals are monitoring their memories,” Smith says. He notes another, less lofty similarity between animal and human behavior: When given the choice between playing hours of video games or getting free food, the monkeys he worked with reached for the joystick.