Subtitles section Play video Print subtitles From the 1890 until his death in 1939, the Austrian physician Sigmund Freud developed psychoanalysis, a method of investigation of the mind and the way one thinks a systematized set of theories about human behavior and a form of psychotherapy to treat psychological or emotional distress especially unconscious conflict. Freud's psychoanalytic theory was largely based on interpretive methods introspection and clinical observations. It became very well known largely because it 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. Clinically, Freud helped to pioneer the method of free association and a therapeutic interest in dream interpretation. Freud had a significant influence on Swiss psychiatrist Carl Jung whose analytical psychology became an alternative form of depth psychology. Psychoanalytic theory and therapy were criticized by psychologists such as Hans Eysenck and by philosophers including Karl Popper. Popper, a philosopher of science, argued that psychoanalysis had been misrepresented as a scientific discipline whereas Eysenck said that psychoanalytic tenets had been contradicted by experimental data. By the end of 20th century, psychology departments in American universities had become scientifically oriented marginalizing Freudian theory and dismissing it as a "desiccated and dead" historical artifact. Meanwhile, however, researchers in the emerging field of neuro-psychoanalysis defended some of Freud's ideas on scientific grounds while scholars of the humanities maintained that Freud was not a "scientist at all, but ... an interpreter."