The purpose of this book is to describe a theory of brain function aimed mainly at an understanding of the biological bases of perception. The theory of neuronal group selection addresses this problem by attempting to answer several key questions. How are connections specified in large neuronal populations? What principles determine the organization of representations and maps in the nervous system? What are the bases in neural structure of perceptual categorization and generalization? The theory proposed to answer these questions is cast in terms of a rigorously selectionist view relating brain development and evolution to structure and function. In the theory, population thinking, the central theoretical mode of biology itself, is applied to individual brains functioning in somatic time. The theory insists that an adequate explanation of higher brain functions first requires an explanation of those developmental constraints on evolution that lead to somatic variation in both brain structure and brain function. Selection of functional variants from neural populations that emerge as a result of this variation during an individual's development is held to be the central principle underlying behavior. This approach is not at present accepted, nor does it have strong antecedents in the history of a science replete with speculations in other categories of ideas.
To be scientifically sensible at this stage of our knowledge, certain constraints must be put on any attempt to relate the brain to psychological activity. In undertaking this theoretical task, I have therefore limited myself stringently to what might seem to a cognitive psychologist to be a very restricted set of psychological functions. I hardly touch upon some of the grand themes that run through William James's ( 1890, republished 1950) magnificent Principles. Consideration of a more modern list ( Norman 1981) of the "essential twelve issues" -- belief sys-