From the 1890s until his death in 1939, the Austrian physician Sigmund Freud developed a method of psychotherapy known as psychoanalysis. Freud was a neurologist whose understanding of the mind was largely based on interpretive methods, introspection and clinical observations, and was focused in particular on resolving unconscious conflict, mental distress and psychopathology. Freud's theories became very well-known, largely because they tackled subjects such as sexuality, repression, and the unconscious mind as general aspects of psychological development. These were largely considered taboo subjects at the time, and Freud provided a catalyst for them to be openly discussed in polite society. While Freud is perhaps best known for his tripartite model of the mind, consisting of the id, ego, and superego, and his theories about the Oedipus complex, his most lasting legacy may be not the content of his theories but his clinical innovations, such as the method of free association and a clinical interest in dreams. Freud also had a significant influence on Carl Jung, whose analytical psychology became an alternative form of depth psychology. Other well-known psychoanalytic thinkers of the mid-twentieth century included Erik Erickson, Anna Freud, Melanie Klein, D.W. Winnicott, Karen Horney, Erich Fromm, and John Bowlby. Philosopher Karl Popper argued that Freud's psychoanalytic theories were presented in untestable form. Psychology departments in American universities today are scientifically oriented, and Freudian theory has been marginalized, being regarded instead as a "desiccated and dead" historical artifact, acccording to a recent APA study. Contemporary psychoanalysis comprises diverse schools of thought, including ego psychology, object relations, interpersonal, Lacanian, and relational psychoanalysis. Modification of Jung's theories has led to the archetypal and process-oriented schools of psychological thought.