No one can learn how to play solitaire by simply watching a player's hands. The trick is knowing where a particular card is supposed to go. In new research, monkeys learned a task almost as sophisticated--they learned a sequence of images by figuring out the successful strategy of another monkey. The results suggest that rhesus macaques learned with their thinking cap rather than merely copying the hand movements of other monkeys.
For more than 100 years, scientists have tried to determine whether animals learn by copying what they see others do or by suffering through trial and error. Although many experiments have shown that they can mimic others, they might not be actively thinking about the process. Anthropologist Herbert Terrace of Columbia University in New York City and colleagues decided to remove the motor aspect of behavior imitation and find out if monkeys could imitate by thinking.
To do so, the team put two rhesus macaques into side-by-side soundproofed chambers, each with a touch-screen computer. One monkey learned to touch four images on the screen in a particular order, earning a banana snack. Each time the images came up, however, they were placed differently on the screen.
After the first monkey mastered a list, the researchers removed a partition that divided the two chambers so the second monkey, who had yet to learn the list, could watch the first monkey work. Through observation, the monkey learned the sequence of images almost twice as fast than when he learned the sequence on his own. The two computers showed images in different configurations, so simply aping the motions wouldn't win a treat.
The authors' approach to separating thought and movement is "clever," says experimental psychologist Thomas Zentall at the University of Kentucky in Lexington. The study is a "good first step," he says, toward proving that monkeys learn through cognitive--not motor--imitation.
Herbert Terrace's Web site with video of monkey tests