Is differential item difficulty specific to hypnosis?
Previous hypnosis studies obtaining retrospective depth reports (e.g., Perry & Laurence, 1980) or retrospective realness reports (e.g., Page & Handley, 1992) have found a “parallel nonoverlapping” pattern between mean depth or realness and susceptibility scale items for high- through low-susceptible subjects. To determine if such a pattern, as well as differential item difficulty in general, is specific to hypnosis, 98 undergraduates were administered the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) of Shor and Orne (1962) as a “test of visual and motor imagination,” omitting the eye-closure induction (item #2). A pattern similar to other studies that employed hypnosis was produced. While supporting attribution theory (Bowers, 1973), results also indicate that differences in item difficulty are not specific to hypnosis, but instead are related more broadly to imagination.
