It emerged in the 1950s in reaction to both behaviorism and psychoanalysis. It stresses a phenomenological view of human experience and seeks to understand human beings and their behavior by conducting qualitative research. The humanistic approach has its roots in existentialist thought (see Heidegger, Nietzsche, Sartre and Kierkegaard). The founding theorists behind this school of thought are Abraham Maslow, who presented a 'hierarchy of human needs'; Carl Rogers, who created and developed 'client centered therapy' and Fritz and Laura Perls who helped create and develop Gestalt therapy. Gestalt psychologists claim to consider behaviour holistically - "the whole is greater than the sum of its parts" - although critics such as Karl Popper have presented forceful arguments against the proposition that entities can be apprehended as wholes.
Humanistic psychologists use a narrow definition of humanism. The American Humanist Association, for example, has had as members many psychologists whom humanistic psychologists would not consider humanist, B. F. Skinner being perhaps the most prominent example.