National Geographic : 2008 Mar
primates. But parrots, like great apes (and humans), live a long time in complex socie ties. And like primates, these birds must keep track of the dynamics of changing relationships and environments. "They need to be able to distinguish colors to know when a fruit is ripe or unripe'"Pepperberg noted. "They need to categorize things-what's edible, what isn't-and to know the shapes of predators. And it helps to have a concept of numbers if you need to keep track of your flock, and to know who's single and who's paired up. For a long-lived bird, you can't do all of this with instinct; cognition must be involved." Being able mentally to divide the world into simple abstract categories would seem a valu able skill for many organisms. Is that ability, then, part of the evolutionary drive that led to human intelligence? Charles Darwin, who attempted to explain how human intelligence developed, extended his theory of evolution to the human brain: Like the rest of our physiology, intelligence must have evolved from simpler organisms, since all animals face the same general challenges of life. They need to find mates, food, and a path through the woods, sea, or sky-tasks that Darwin argued require problem-solving and categorizing abilities. Indeed, Darwin went so far as to suggest that earthworms are cognitive beings because, based on his close observations, they have to make judgments about the kinds of leafy matter they use to block their tunnels. He hadn't expected to find thinking invertebrates and remarked that the hint of earthworm intel ligence "has surprised me more than anything else in regard to worms." To Darwin, the earthworm discovery dem onstrated that degrees of intelligence could be VirginiaMorell, a science writer based in Oregon, is a frequent contributorto National Geographic. Vincent J.Musi lives in South Carolinaand shoots diverse topicsfor National Geographic and Time. 48 NATIONAL GEOGRAPHIC * MARCH 2008 found throughout the animal kingdom. But the Darwinian approach to animal intelligence was cast aside in the early 20th century, when researchers decided that field observations were simply "anecdotes," usually tainted by anthro pomorphism. In an effort to be more rigorous, many embraced behaviorism, which regarded animals as little more than machines, and focused their studies on the laboratory white rat-since one "machine" would behave like any other. But if animals are simply machines, how can the appearance of human intelligence be ex plained? Without Darwin's evolutionary per spective, the greater cognitive skills of people did not make sense biologically. Slowly the pendulum has swung away from the animal as-machine model and back toward Darwin. A whole range of animal studies now suggest that the roots of cognition are deep, widespread, and highly malleable. ust how easily new mental skills can evolve is perhaps best illustrated by dogs. Most owners talk to their dogs and expect them to understand. But this canine talent wasn't fully appreciated until a border collie named Rico ap peared on a German TV game show in 2001. Rico knew the names of some 200 toys and ac quired the names of new ones with ease. Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig heard about Rico and arranged a meeting with him and his owners. That led to a scientific report revealing Rico's uncanny language ability: He could learn and remember words as quickly as a toddler. Other scientists had shown that two year-old children-who acquire around ten new words a day-have an innate set of principles that guides this task. The ability is seen as one of the key building blocks in language acquisi tion. The Max Planck scientists suspect that the same principles guide Rico's word learning, and that the technique he uses for learning words is identical to that of humans.