John B. Watson
In 1913, Watson viewed Ivan Pavlov's conditioned reflex as primarily a physiological mechanism controlling glandular secretions.  He had already rejected Edward Thorndike's "Law of Effect" (a precursor to B.F. Skinner's principle of reinforcement) because of what Watson believed were 'unnecessary subjective elements'. The article is also notable for its strong defense of the objective scientific status of applied psychology, which at the time was considered to be much inferior to the established experimental psychology.