Can a parrot understand complex concepts and mean what it says? Since the early 1900s, most studies on animal-human communication have focused on great apes and a few cetacean species. Birds were rarely used in similar studies on the grounds that they were merely talented mimics--that they were, after all, "birdbrains." Experiments performed primarily on pigeons in Skinner boxes demonstrated capacities inferior to those of mammals; these results were thought to reflect the capacities of all birds, despite evidence suggesting that species such as jays, crows, and parrots might be capable of more impressive cognitive feats. Twenty years ago Irene Pepperberg set out to discover whether the results of the pigeon studies necessarily meant that other birds--particularly the large-brained, highly social parrots--were incapable of mastering complex cognitive concepts and the rudiments of referential speech. Her investigation and the bird at its center--a male Grey parrot named Alex--have since become almost as well known as their primate equivalents and no less a subject of fierce debate in the field of animal cognition. This book represents the long-awaited synthesis of the studies constituting one of the landmark experiments in modern comparative psychology.