behaviorism, school of psychology which seeks to explain animal and human behavior entirely in terms of observable and measurable responses to environmental stimuli. Behaviorism was introduced (1913) by the American psychologist John B. Watson, who insisted that behavior is a physiological reaction to environmental stimuli. He rejected the exploration of mental processes as unscientific. The conditioned-reflex experiments of the Russian physiologist Ivan Pavlov and the American psychologist Edward Thorndike were central to the development of behaviorism. The American behaviorist B. F. Skinner contended that all but a few emotions were conditioned by habit, and could be learned or unlearned. The therapeutic system of behavior modification has emerged from behaviorist theory. Therapy intends to shape behavior through a variety of processes known as conditioning. Popular techniques include systematic desensitization, generally used on clients suffering from anxiety or fear of an object or situation, and aversive conditioning, employed in cases where a client wishes to be broken of an unhealthy habit (such as smoking or drug abuse). Other behavior therapies include systems of rewards or punishments, and modeling, in which the client views situations in which healthy behaviors are shown to lead to rewards.
See B. F. Skinner, Science and Human Behavior (1965); J. B. Watson, Behaviorism (1930, repr. 1970); J. O'Donell, Origins of Behaviorism (1986); K. W. Buckley, Mechanical Man: John B. Watson and the Beginning of Behaviorism (1989).