This book is the result of an international symposium in biological psychology, held in honor of Knut Larsson. This renowned researcher — in his search for the true meaning of ‚mind vs. matter‘ — became involved in many divergent areas of the field, such as the neurobiology of sexual behavior and sexual differentiation, aspects of functional neuroanatomy, behavioral endocrinology, and psychopharmacology. Through experimentation and much consultation with other area specialists, Larsson observed such phenomena as the adaptation of behavior-determining neuroendocrine events to the physical environment and the hormonal regulation of sexual behavior and differentiation. This tribute to his research presents important features of necessary paradigms for the analysis and study of experimental psychology within the biological perspective.