Watson took as its object of psychology behavior. The founder of Behaviorism has given psychology consistency by having an observable, measurable object of study. The experiments of this science could be reproduced in the laboratory, under different conditions and in different subjects. This perspective led to the rupture of Psychology with Philosophy, since before Psychology acquired the status of science, in the positivist sense of the term, it had as its object the study of the soul, and thus fit within the philosophical studies. Watson defended the functionalist conception.
Skinner stated that all human behavior could be shaped by controlling the stimuli of the environment. According to his theory, it would be possible to create or exclude behaviors by inserting or eliminating stimuli in the environment. Environmental stimuli were identified and termed by the behaviorist psychologist as: positive reinforcement, negative reinforcement, and punishment. Positive reinforcement is the stimulus applied by the researcher to an organism soon after it has behaved as desired by the researcher.
Functionalism can be considered as one of the first schools of thought in modern psychology. Functionalists emphasized that the focus of psychology should be on the functioning of the human mind. Behaviorists, however, claimed that it was a futile attempt and stressed the need to study human behavior. This is the fundamental difference between functionalism and behaviorism.