How do we sort the objects, people, events, and ideas in the world into their proper categories so that we may experience and interact with them? This fundamental question about human--and animal--perception and cognition is the subject of Categorical Perception, a comprehensive survey of a wide range of important research findings on the subject. The volume brings together all known examples of categorical perception, from research on humans and animals, infants and adults, in all the sense modalities: hearing, seeing, and touch. The perceptual findings are then interpreted in terms of the available cognitive and neuroscientific theories of how categorical perception is accomplished by the brain. Research on elementary perceptual and psychophysical categories is then compared with work on higher order categories such as objects, patterns, and abstract concepts. The book proceeds to an integrative view of categorization in general by exploring the most thoroughly investigated case of categorical perception--speech perception.