Prism Adaptation in hypnotically limb-anesthetized subjects: more disconfirming data.

Abstract

Two experiments assessed the effect of hypnotically suggested arm anesthesia on adaptation to displacing prisms. In Study 1, 30 highly susceptible subjects adapted to prisms by pointing at a visual target for 2 min. with their hypnotically anesthetized dominant arm. Suggestion and hypnosis were then "lifted," and subjects were randomly assigned to three groups: subjects in one group were asked to move the hand slowly during the posttest (slow motion); those in a second group were told that hypnotic anesthesia would enable them to overcome displacement aftereffects (hypothesis informed); the remaining subjects (controls) were given no special instructions. During posttesting, all groups showed a significant displacement aftereffect, with no differences occurring between groups. Study 2 followed the same procedure except that during adaptation the usual target was removed and subjects pointed towards a homogeneous backboard. 20 highly susceptible subjects were assigned to an hypothesis-informed or control group immediately before posttesting. All subjects showed a significant displacement aftereffect. Both studies provide further evidence that hypnotic suggestions do not influence automatic perceptual processes. The results of Exp. 2 contradict the suggestion that hypnotic limb anesthesia eliminates the displacement aftereffect when the target is removed during adaptation trials.