From Psychology as the Behaviorist Views It, by John B. Watson, Psychological Review, 1913:
"Psychology as the behaviorist views it is a purely objective experimental branch of natural science. Its theoretical goal is the prediction and control of behavior. Introspection forms no essential part of its methods, nor is the scientific value of its data dependent upon the readiness with which they lend themselves to interpretation in terms of consciousness. The behaviorist, in his efforts to get a unitary scheme of animal response, recognizes no dividing line between man and brute. The behavior of man, with all of its refinement and complexity, forms only a part of the behaviorist's total scheme of investigation...
The time seems to have come when psychology must discard all reference to consciousness; when it need no longer delude itself into thinking that it is making mental states the object of observation. We have become so enmeshed in speculative questions concerning the elements of mind, the nature of conscious content (for example, imageless thought, attitudes, etc.) that I, as an experimental student, feel that something is wrong with our premises and the types of problems which develop from them... I firmly believe that two hundred years from now, unless the introspective method is discarded, psychology will still be divided [over questions that cannot be resolved scientifically]."
The introspective study of conscious experience, advocated by Descartes for studying the mental world proved to be too unreliable and unverifiable to be part of science. Watson proposed that psychology adopt a new paradigm, 'behaviorism':
The paradigm of behaviorism:
The subject matter of psychology: psychology is the study of the relationship between stimuli and behavior (both stimuli and behavior can be directly measured).
The method of psychology: To manipulaye stimuli and observe the effect upon behavior.
The joke going around at the time was that psychology, having first lost its soul, had now lost its mind.
John Watson: Founder of Behaviorism
"In 1903, [Watson] received his Ph.D., married, and remained at the University of Chicago as an instruction until 1908....[he] engaged in much research, demonstrating early his preference for animal subjects. As he stated in his autobiographical sketch:
'I never wanted to use human subjects. I hated to serve as a subject. I didn't like the stuffy, artificial instructions given to subjects. I always was uncomfortable and acted unnaturally. With animals I was at home. If felt that, in studying them, I was keeping close to biology with my feet on the ground. More and more the thought presented itself; Can't I find out by watching their behavior everything that the other students are finding out by using [human subjects]?'
...Watsonian behaviorism appealed to many younger psychologists who felt that Watson was cleansing the muddled atmosphere of psychology by casting off the long-standing mysteries and uncertainties carried over from philosophy. The rapid acceptance of his position was evidenced by his election to the presidency of the American Psychological Association in 1915--just 2 years after his paper appeared. He was then 37 years of age.
...Watson's highly promising career lasted only 17 years; it ended abruptly and tragically in 1920. The sensationalized nationwide publicity accorded divorce proceedings brought against him resulted in his forced resignation from Johns Hopkins University, and he never returned to a full-time university position." He turned his energies to a new career, and became successful in the field of advertising.