Having briefly and succinctly described the methods of behavioral and molecular genetics, epidemiology, neurobiology, and neuropsychology, Pennington divides the areas of psychopathology to be considered into disorders of motivation, disorders of action regulation, and disorders of language and cognitive development. The disorders of motivation include depression and dysthymia, the anxiety disorders, posttraumatic stress disorder, and bipolar disorder. Beginning with the definitions, moving on to distribution in populations, epidemiology, and brain mechanisms so far as they are currently understood, Pennington discusses the major psychological theories, including those of Freud, Seligman, and Beck, and the theories of reinforcement. After reviewing these theories and demonstrating the social integration that demonstrates the incompleteness of each, he presents a section on treatment. Again, empirical data are presented regarding pharmacological and psychosocial treatments. The same scheme is followed in the disorders of action regulation, which include attention deficit hyperactivity disorder, conduct disorder, Tourette’s syndrome, obsessive-compulsive disorder, and schizophrenia. Particularly interesting are the disorders of language and cognitive development, including autism, mental retardation, dyslexia, and other language disorders. These are treated in some detail, including findings on structural neuroimaging studies and genetics. Because these disorders touch more directly on the fundamental processes of thinking, they are particularly important to the understanding of the developmental approach. Distinctions between the spatial cognition of Williams syndrome and autism, and the various forms of dyslexia and other language disorders, bring us closer to understanding the brain mechanisms of all sorts of thinking.