History and Systems of Psychology

The system that defines psychology as the study of behavior received firm support in a twentieth-century development that occurred largely in the United States. Observable and quantifiable behavior was assumed to have meaning in itself, rather than simply serving as a manifestation of underlying mental events. This movement was formally initiated by an American psychologist, John Broadus Watson (1878–1958), in a famous paper, “Psychology as the Behaviorist Views It,” published in 1913. Watson proposed a radical departure from existing formulations of psychology by asserting that the proper direction for psychology's development is not the study of “inner” consciousness. In fact, he dismissed the entire notion of some nonphysical mental state of consciousness as a pseudo-problem for science. In its place Watson advocated overt, observable behavior as the sole legitimate subject-matter for a true science of psychology.

Watson was largely successful in initiating a redirection of the development of psychology. Later in this chapter we examine the various intellectual forces that converged in Watson's time and fostered the acceptance of his views. Although Watson may have been the spokesperson for a revolutionary movement defining the scope of psychology, it should be recognized that the subsequent success of the behaviorist movement in psychology is best characterized as evolutionary rather than revolutionary. Behaviorism, especially in the United States, gradually changed from Watson's initial definition to one that encompassed a wide range of human and infrahuman activity, studied under varieties of empirical methodologies.

The historical trend that led to Watsonian behaviorism may be traced from antiquity to the nineteenth century. The pre-Socratic philosophers, such as the Ionian physicists and Hippocrates (Chapter 3), attempted to explain human activity as mechanical reactions reducible to biological or physical causes. Much later, the French sensationalist tradition (Chapter 8), rejecting Descartes’ unextended substance in favor of a mechanical system responding to environmental stimuli, served as an important predecessor of twentieth-century behaviorism. Both the sensory reductionism of Condillac and the mechanical physiology of La Mettrie led to the position that mental events are determined completely by sensory input and that the critical level of psychological inquiry concerns sensory processes. Perhaps the British philosophers (Chapter 9), provided behaviorism with its clearest intellectual foundation.