Based upon two decades of research with patients who have experienced pathology in one hemisphere of the brain, this book deals with brain mechanisms in human communicative behaviour, and with related motor functions from a broadly biological point of view. The work discusses the possible evolutionary origins of human communication, the relation of brain mechanisms in communicative behaviour to analogous nonhuman behaviors, and the neural systems involved in various levels and kinds of communication. Noncommunicative mechanisms which parallel those used in communication are also outlined in detail. Individual differences in brain organization for some functions are also explored. Much new data is presented along with the theoretical treatment of human communication which emphasizes a behavioral rather than a linguistic approach. The work will interest psycholinguists, cognitive psychologists, neurologists, clinical neuropsychologists, speech pathologists, and advanced students in these fields.