Humanistic psychology is a psychological perspective which rose to prominence in the mid-20th century in response to Sigmund Freud's psychoanalytic theory and B. F. Skinner's Behaviorism. The approach emphasizes an individual's inherent drive towards self-actualization and creativity. Psychologists Carl Rogers and Abraham Maslow introduced a positive, humanistic psychology in response to what they viewed as the overly pessimistic view of psychoanalysis in the early 1960s. Other sources include the philosophies of existentialism and phenomenology.