Book excerpt: Biology and Neurophysiology of the Conditioned Reflex and its Role in Adaptive Behavior explores the conditioned reflex, its historic development, and its functions and roles. The book also aims to bridge the gap between the integrative level of higher nervous activity and fine detailed neurophysiological investigations, giving light to the basis of the term "learning. The book, as an introduction, covers the biological roots of the conditioned reflex and the nature of the unconditioned reflex, then moves on to the different bases, hypotheses, and theories of both the coupling of the conditioned reflex; the physiological architecture of the behavioral act; the mechanism of action and function of conditioned inhibition function; and certain correlations in the study of this phenomenon. The text is recommended for biologists, zoologists, psychologists, and neuroscientists from different backgrounds who wish to know more about how the conditioned reflex, and ultimately learning, came about.