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Crows, for example, have proved themselves adept at bending wire to create a hook so they can fish a basket of food from the bottom of a plastic tube. More remarkably, last year a zoologist at the University of Cambridge the aptly named Christopher Bird found that the rook, a member of the crow family, could reason through how to drop stones into a pitcher partly filled with water in order to raise the level high enough to drink from it. What's more, the rooks selected the largest stones first, apparently realizing they would raise the level faster. Aesop wrote a tale about a bird that managed just such a task more than 2,500 years ago, but it took 21st century scientists to show that the feat is no fable.
How the birds performed such a stunt without a cerebral cortex probably has something to do with a brain region they do share with mammals: the basal ganglia, more primitive structures involved in learning. Mammalian basal ganglia are made up of a number of structures, while those in birds are streamlined down to one. Earlier this year, a collaborative team at MIT and Hebrew University of Jerusalem found that while the specialized cells in each section of mammalian basal ganglia do equally specialized work, the undifferentiated ones in birds' brains multitask, doing all those jobs at once. The result is the same information is processed but birds do it more efficiently.
In the case of corvids and other animals, what may drive intelligence higher still is the structure not of their brains but of their societies. It's easier to be a solitary animal than a social one. When you hunt and eat alone, like the polar bear, you don't have to negotiate power struggles or collaborate in stalking prey. But it's in that behavior particularly the hunt that animals behave most cleverly.
Consider the king of the beasts. "Lions do very cool things," says animal biologist Christine Drea of Duke University. "One animal positions itself for the ambush, and another pushes the prey in that direction." More impressive still is the unglamorous hyena. "A hyena by itself can take out a wildebeest, but it takes several to bring down a zebra," she says. "So they plan the size of their party in advance and then go out hunting particular prey. In effect, they say, Let's go get some zebras. They'll even bypass a wildebeest if they see one on the way."
Last year, Drea conducted a study of hyena cooperation, releasing pairs of them into a pen in which a pair of ropes dangled from an overhead platform. If the animals pulled the ropes in unison and only in unison the platform would spill out food. "The first pair walked into the pen and figured it out in less than two minutes," Drea says. "My jaw literally dropped."
For these kinds of animals, it's not clear what the cause-and-effect relationship is whether living cooperatively boosts intelligence or if innate intelligence makes it easier to live cooperatively. It's certainly significant that corvids are the most social of birds, with long lives and stable group bonds, and that they're the ones that have proved so handy. It's also significant that herd animals, like cows and buffalo, exhibit little intelligence. Though they live collectively, there's little shape to their society. "In a buffalo herd, Bob doesn't care who Betty is," Drea says. "But among primates, social carnivores, whales and dolphins, every individual has a particular place."
Self and Other
It's easy enough to study the brain and behavior of an animal, but subtler cognitive abilities are harder to map. One of the most important skills human children must learn is something called the theory of mind: the idea that not all knowledge is universal knowledge. A toddler who watches a babysitter hide a toy in a room will assume that anyone who walks in afterward knows where the toy is too. It's not until about age 3 that kids realize that just because they know something, it doesn't mean somebody else knows it also.
The theory of mind is central to communication and self-awareness, and it's the rare animal that exhibits it, though some do. Dogs understand innately what pointing means: that someone has information to share and that your attention is being drawn to it so that you can learn too. That seems simple, but only because we're born with the ability and, by the way, have fingers with which to do the pointing.