He had already rejected Edward L. Thorndike 's `` Law of Effect '' ( a precursor to B. F. Skinner 's principle of reinforcement ) due to what Watson believed were unnecessary subjective elements .
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 ' .