Gazzaniga is well known among neuroscientists for his searching analyses of changes in perception and interpretation seen in ""split-brain"" patients tested under conditions of restricted vision. These individuals have had the connections between right and left cerebral hemispheres severed, with the result that the hemispheres work independently. It was partly based on this work that Gazzaniga, now at Cornell Medical Center in New York, conceived the notion that there is an interpreter mediating between mind and brain--a kind of agent who tries to make sense of sensations and ""felt changes in body chemistry."" The interpreter (in classic Western tradition) apparently is hellbent on finding reasonable explanations and may then store them, building up a memory and history. As a way to deal with the ""mind-brain"" problem, this approach is not unlike the role of ego in Freud, Descartes' soul, or the little homunculus sitting in the brain viewing the retinal screen (and hence giving rise to an even smaller dwarf sitting in the homunculus' brain. . .ad infinitum). As a semantic device to approach the many absorbing phenomena Gazzaniga examines--pain, addiction, intelligence, love, schizophrenia, anxiety, depression, obsessions, compulsions, sleeping/dreaming, stress, healing--it has its points. For example, Gazzaniga views schizophrenia as a disease in which the interpreter goes wild in trying to bring order out of brain chaos induced by chemical imbalances. Phobias may result from the interpreter associating the context of a panic attack (a crowded subway, for example) and sealing it in memory. Semantics aside, Gazzaniga provides a wealth of up-to-date information on brain chemistry, genetics, changes in aging, adaptation to injury, newly discovered relations between the brain and the immune system, and myriad other important findings, in a style that manages to combine rigor with wit.