J. B. Watson and Behaviorism
In the early twentieth century a new movement in the field of Psychology was being felt in educational research — behaviorism. This is a theory proposed by J. B. Watson and based on the works of Pavlov and Bekhterev, two Russian psychologists who developed an animal training model known as stimulus-response (Classical Conditioning).
Watson argued that such conditioning is the basis of human behavior — if you stand up every time a lady enters the room, you're acting not out of “politeness,” but because behavior is a chain of well-set reflexes. He claimed that “recency” and “frequency” were particularly important in determining what behavior an individual “emitted” next — if you usually get up when a lady enters the room, you're likely to get up if one enters now.