These three approaches each seem to focus on more "tangible" types of evidence, not any physiological evidence or reasons. The first two, Behaviorism and Psychodynamic, both focus on how specific stimuli may affect or cause certain behaviors. Whereas the third, Humanistic, is more concerned with the uniqueness of the individual.
The behavioral perspective was first introduced through the studies of Russian physiologist, Ivan Pavlov. While studying digestion in dogs, Pavlov realized that the dogs had begun to associate certain sights or sounds with being fed (Davis and Palladino, p. 25). In this case, the dogs began to salivate when they saw the food dish or heard the jangling of keys, not just when they were actually fed. This linking of two unrelated stimuli, to elicit a specific reflexive reaction or UCR (unconditioned response), is an example of a learned behavior.
This belief that only observable behavior should be the main focus of psychology was continued by the works of John B. Watson and B.F. Skinner. Watson believed that thinking, feeling, or consciousness should not be considered because it was not observable (Davis and Palladino, p. 195). They believed that learning was a permanent change in behavior caused only by environmental factors or consequences.
Eventually this theory was disregarded because it was too restrictive in its beliefs of how behaviors are affected.
The second theory, the Psychodynamic Perspective, was developed at approximately the same time by Sigmund Freud, a name still widely recognized.
Freud believed, however, that it was necessary to go far beyond observable behaviors. His theories were concerned with the unconscious forces that affected both normal and abnormal behaviors (Davis and Palladino, p. 25).
According to Freud, the two main things that affected behavior were early...