Wit on the Wing

Every northerner knows ravens are smart. In the early beliefs of Scandinavians, ravens perched on the shoulders of the chief of gods, whispering wisdom gained on far-seeing flights. Native Alaskans told of Raven who brought light to humankind, clever Raven who could fool chiefs and spirits, wise raven who liberated infant humankind from its imprisoning shell.

In contemporary conversations, we swap smart-raven stories, how they snitched windshield wiper blades in North Pole, how they slid on their tail feathers down snow chutes above Dutch Harbor, how they figured out which fast-food places offered the best pickings in Southeast. Everyone has raven stories. Everyone knows they're smart.

But try to prove that.

The problem is that virtually brainless behavior can look intelligent. Consider honeybees, for example. They live within complex social structures; they construct geometrically precise and functionally effective homes; they even communicate important information to one another, such as directions and distances to food sources. It's impressive, but it's instinct, not intellect, in action. A thoughtful bee has yet to be born.

Raven expert Bernd Heinrich decided to see if the birds could show one kind of creative thought process: insight. Insight involves the ability to envision one's actions and their consequences. An insightful creature runs a mental movie, so to speak, visualizing a problem and its solution. It's looking inside to see what will happen before it moves a muscle.

In his account in the October 1993 issue of Natural History, Heinrich cites a famous example of nonhuman insight. An experimenter hung bananas high up in a room containing six chimpanzees and a large wooden crate. Five of the chimpanzees jumped up and down, futilely trying to reach the food. One chimpanzee hung back, watching the others until they calmed down. Then he shoved the crate under the bananas, jumped atop it, and snatched the fruit. That was an insightful ape. No one showed him how; he figured it out.

Heinrich devised an experiment to set ravens a problem that only creative thinking could solve. At his New England home, Heinrich has a large, outdoor aviary housing some tame crows and ravens. The aviary holds trees and one long horizontal perch. From the perch, the scientist hung a piece of string 25 inches long. Tied to the dangling end of the string was a chunk of meat.

The chunk was too small for the birds to sit on while they pecked at it. The only way they could get to eat some of it was by hauling it up to the perch, but they had never had any experience with string. They had to figure it out.

Presented with this puzzle, Heinrich's five tame ravens apparently studied the situation. They immediately examined the meat, then left it alone for nearly six hours, except for occasional glances. Then one raven flew to the perch, landed directly above the meat, and reached down to grab the string. He pulled up a loop, then stepped on it to hold it fast, and reached down to pull up another loop. The bird continued the pull-step-pull behavior until it had the meat up on the perch. Heinrich shooed it away before it could eat, but the bird did not hold onto the meat. It had not only figured out how to get the meat, it had also recognized that the meat was fastened and would not fly away when the bird did.

By the end of the experiment, three of the ravens had figured out how to get the meat. None tried to fly away with it. (The crows never did decipher the puzzle, and when given attached meat they would fly off, only to receive a sharp jerk when they hit the end of the string.)

Is that scientific proof? It's at least strong evidence that ravens really are intelligent.