Methodological behaviorism was pioneered by researcher John B. Watson in the early decades in the 20th century This particular perspective on psychology concentrated only on the observation of observable cause and effect reactions without consideration of the mental components of behavior and the intellectual workings of the subject’s mind. This particular study was an expansion of the observations of physical cause and effect that were made by Pavlov in the 19th century. In the 1930’s, B.F. Skinner chose to add study of the intellectual workings of behaviorism in a school of thought known as radical behaviorism.