Two Leaders in the Development of Humanistic Psychology Carl Rogers and Abraham Maslow were key figures in establishing humanistic psychology. Humanistic psychology emphasized the importance of self-determination, creativity, and human potential (Serlin, 2012). The ideas of Carl Rogers have been particularly influential in modern psychotherapy. Abraham Maslow’s theory of motivation emphasized the importance of psychological growth.(l) Special Collections, Donald C. Davidson Library/University of California, Santa Barbara(r) Courtesy of Robert D. Farber University Archives at Brandeis University