Specializations do not make one species "smarter" than another, but they do make for uniquely sculpted minds.
Do animals think? And if they do, how similar are their thoughts to our own? Traditionally, scientists have taken two approaches to cognition in animals, with the "liberals" (often those who study wild animals) arguing that there are clear parallels between animal and human thinking and the "skeptics" (often those who focus on captive animals) defending the uniqueness of the human mind. Harvard psychologist Marc Hauser is in an ideal position to evaluate the nuances of both positions, because in addition to observing and running experiments on cotton-top tamarins in the lab, he has studied vervet monkeys in the Kenyan savanna, chimpanzees in a Ugandan rainforest, rhesus monkeys on a Caribbean island, and crows on a California golf course. Plus lie knows and lucidly cites the work of the evolutionary biologists, ethologists, neuroscientists, developmental psychologists, and cognitive scientists who have contributed to this burgeoning field.
Hauser introduces us to an extraordinary range of feats of cognition by animals-from the New Caledonian crow, which constructs and modifies tools, to Clark's nutcracker, which uses its extraordinary spatial memory to locate during the winter the 30,000 or so pine nuts that it stored during the fall. In this thoughtful book, Hauser gives evidence to support both the skeptical and the liberal camp. Believing that language is unnecessary for certain kinds of animal cognition, and that we must look at the emvironments in which animals evolved to understant what they think and feel, he concludes, "We share the planet with thinking animals."
All animals, according to Hauser, have the mental tools for three distinct tasks: recognizing objects, evaluating quantity@ and navigation. But how do we know that animals universally possess these capacities, and how do these abilities expand or contract in particular species? In experiments with tamarins and macaques, Hauser adapted a technique used by developmental psychologists to show that preverbal infants understand cause and effect, are able to discriminate quantity, and know that objects exist even when they can't be seen. Like infants, Hauser's monkeys show little interest when two toys are lowered behind a screen and the same two toys are revealed when the screen is raised. But both monkeys and infants demonstrate that they know when the number has changed: if there is only one toy or if there are two different toys when the screen is raised, both look longer at the scene.
Other cognitive abilities appear to be restricted to a few species. Great apes that encounter mirrors demonstrate self-awareness. If a researcher surreptitiously places a mark on a part of the ape's face that it can see only by using the mirror, some of these animals react by immediately grooming the spot, suggesting that they recognize images of themselves. To date, however, no monkeys have unequivocally passed this test, so perhaps self-recognition and self-awareness are mental properties limited to humans and apes.
Self-awareness is closely related to another ability: awareness of what others know and don't know. Teaching requires this skill, as does successful, deliberate deception. …