He developed a theory of psychodynamics which, simply stated, proposed that people can have multiple and conflicting motives, and that if a force is not expressing itself, then there must be another force blocking it. These psychodynamic processes, which operated unconsciously to the individual and independent of the brain and nervous system, could be brought to conscious realization by a method of guided introspection he called psychoanalysis. Freud's theories were controversial, but they set the stage for the modern science of psychology. The first major behaviorist was the physiologist, Ivan Pavlov. He accidentally discovered the laws of classical conditioning while studying the digestive processes of dogs.
Dogs normally salivate at the sight and smell of food.
B. F. Skinner carried these investigations further in the twentieth century. He was primarily interested in how human behaviorism is derived from observing the laws of learning. Over the last twenty to thirty years the cognitive-social approach has gained prominence, and it is now the most widely accepted of psychological paradigms. The cognitive approach grew out of behaviorism in that it is concerned with laws of learning. People learn from observing other people.