Rogers was a pioneer in the scientific investigation of psychotherapy. He believed the methods of empirical research could and should be applied to the practice of psychotherapy. He was the first to record psychotherapy sessions despite vehement opposition from the psychoanalysts who believed the privacy of the therapy hour should never be violated. Rogers also systematically measured improvement by administering psychological tests pre-and post-treatment and then compared the results of subjects in therapy with those in a control group. These methods became fundamental tools in psychotherapy research, which has since blossomed into a discipline all its own.