Psychoanalytic: The founder of the psychoanalytic school of thought is Sigmund Freud. He believed that many psychological problems result from the conflicts that occur between "acceptable" behavior and "unacceptable" unconscious sexual or aggressive motives. His theory was called Psychoanalysis. Freud relied more on deductive reasoning rather than on rigorous research methods, hence making his approach non-scientific. Also, he laid emphasis on the importance of unconscious processes and unresolved past conflicts.
Behaviorist: The founder of the behaviorist school of thought is John B. Watson. Behaviorism perspective rejected the notion of the conscious and unconscious mind, but instead focused on the importance of observation and environmental influences on behavior. This school of thought first started with the Pavlov's "classical conditioning", which claimed that behaviors could be learned via conditioned associations Classical conditioning is a learning that occurs by which a neutral stimulus becomes associated with a meaningful stimulus and acquires the capacity to elicit a similar response (Feist, 2008, p. 449). Another famous behaviorist, B.F Skinner, believed in the concept of "operant conditioning", which demonstrated the effect of punishment and reinforcement on behavior. For instance, He claimed that if a behavior is reinforced, it increases the chances of that behavior to be repeated. Similarly, if a behavior is followed with punishment, the chances of that behavior to repeat itself diminish.
Humanist: The two major figures of the humanistic perspective are Carl Rogers and Abraham Maslow. They believed that all individuals have the natural capacity to move towards self actualization. Also, they emphasized on the notion of free will (voluntarily chosen
References: eist, J., & Feist, G. J. (2008) Theories of Personality (7th ed). New York: McGraw- HillJohn Wiley & Sons Inc.. (2008). Visualizing Psychology (1st ed.). NJ: Author.