The Influence of Control Comparison Tasks and Betweenversus Within-Subjects Effects in Hypnotic Responsivity

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Abstract
Type of experimental design (between- versus within-subjects) and type of control task were examined for their differential effects on the magnitude of objective and state report test scores associated with response to items on the Stanford Hypnotic Scale of Susceptibility, Form C (Weitzenhoffer & Hilgard, 1962). In an integrated program of work exploring design effects in hypnotic research, Ss in each of 7 comparison conditions that involved hypnosis and 4 separate comparison conditions that did not involve hypnosis were tested twice on successive occasions. Three of the control tasks used (waking, imagination, and imagination [alert] instruction) were counterbalanced with hypnosis to analyze possible order effects associated with hypnotic test conditions. Data indexed the patterns of between- versus within-subjects effects associated with standard control tasks and also highlighted the order effects that accompanied them. Imagination instructions, in particular, pose specific difficulties that require attention when Ss are tested as their own controls.