<P> During the first half of the twentieth century , John B. Watson devised methodological behaviorism , which rejected introspective methods and sought to understand behavior by only measuring observable behaviors and events . It was not until the 1930s that B.F. Skinner suggested that private events -- including thoughts and feelings -- should be subjected to the same controlling variables as observable behavior , which became the basis for his philosophy called radical behaviorism . While Watson and Ivan Pavlov investigated the stimulus - response procedures of classical conditioning , Skinner assessed the controlling nature of consequences and also its ' potential effect on the antecedents ( or discriminative stimuli ) that strengthens behavior ; the technique became known as operant conditioning . </P>
who is considered the father of modern behaviorism
John B. Watson