Dr. Harper taught psychology and sociology at Wagner from 1943 to 1945. Harper was interested in conformity in social behavior as indicated in his 1942 dissertation "An exploratory questionnaire study of conforming and nonconforming behavior" which he completed at Ohio State University. His work was truly interdisciplinary drawing from the work of Floyd Allport, considered by some to be the founder of modern social psychology, and Walter Reckless, the sociologist who supervised Harper's dissertation.
Before coming to Wagner, Harper taught at Ohio State and Kent State Universities and was an Area Analyst for the War Manpower Commission (created by President F.D. Roosevelt in 1942) in Ohio. According to the 1945-46 Wagner college Catalog, he "resigned to enter war work." For a year, he worked as a psychiatric social worker in the US Army.
After leaving Wagner and the army, he became a prominent marriage and family counselor. He wrote several books with Albert Ellis, the founder of Rational Emotive Behavior Therapy including Creative Marriage (1961), A Guide to Successful Marriage (1975), and A Guide to Rational Living (1961 with revisions in 1975 and 1998) among others. His Psychoanalysis and Psychotherapy: 36 Systems (1959) was one of his most influential books. His obituary was published in American Psychologist in 2004 (vol. 59, no. 6, p. 562).