On the other hand, Watson denied the role of inheritance as a determinant of behavior since he considered that the conduct is almost exclusively acquired through learning. Today his conception of metaphysical Behaviorism no longer exists.Watson proposed a method for analysis and behavior modification, since for him, the sole object of valid study for psychology was observable behavior. He wanted to make scientific study of Psychology using only objective procedures such as those of the natural sciences for the study of human behaviors. In this way, laid the foundation of what we know today as methodological Behaviorism, which was developed with the passage of time.Although currently Behaviorism is not limited to the study of observable phenomena but also includes internal events (thoughts, images), remains the criterion to relate the theoretical postulates manifest conduct by an approach experimental.We can say that the real takeoff of the behavior therapy occurs after the second world war, developing what is known as neoconductismo. These new behavioral orientations differ to some degree from his predecessors, but at the same time, take many elements of previous learning theorists like Pavlov and Thorndike.A starting from the Decade of the 30, was developed in United States the conditioning operant, as a result of the work conducted by B. F. Skinner and collaborators.

The focus of this psychologist is similar to Watson, that psychology should be the study of observable behavior of individuals in interaction with the environment that surrounds them. Skinner, however, differed from Watson in which internal phenomena, such as feelings, be excluded from the study, holding that they should be studied by the usual scientific methods and giving more importance to the experiments controlled with both animals and humans. His research with animal, centred on the type of learning (instrumental or operant conditioning) that occurs as a result of a stimulus caused by the behaviour of the individual, they proved that the more complex behaviors such as language or solving problems, could study scientifically based on his relationship with the consequences for the subject.In the Decade of the 50 they arise in different places and as a result of the work of independent, current researchers thought that then confluiran.