Watson, John Broadus (1878–1958), American psychologist. Watson popularized the theories of behaviorism in the United States During the 1920s and 1930s Watsonian behaviorism was the dominant school of psychology in the United States, where it still has an enduring influence. Before joining the advertising business in 1921, Watson served as professor of psychology at Johns Hopkins University, where he established a laboratory of comparative psychology. In 1913 he published a manifesto for behaviorist psychology, asserting that psychology, like other sciences, is to be studied under exacting laboratory conditions. In 1919 he published a major work on behaviorist psychology in which he sought to extend the principles and methods of comparative psychology to the study of human beings. His other writings include a book on behaviorism intended for the general reader (1925) and a guide for the psychological care of infants and children (1928).