Carlyle Ferdinand Jacobsen, Stanley Smith Stevens, Ernest Ropiequet Hilgard, and Don Marquis, at an American Psychological Association Conference, 1937, Smithsonian Institution Archives, left to right: Carlyle Ferdinand Jacobsen (1902-1974), Professor of Psychology, Yale University; Stanley Smith Stevens (1906-1973), Professor of Psychology, Harvard University; Ernest Ropiequet Hilgard (1904-2001), hypnosis expert and Professor of Psychology, Stanford University; and Don Marquis, Professor of Psychology, University of Michigan. The photograph was taken April 1937 at a meeting of American Psychological Association..