Psychophysical and signal detection analyses of hypnotic anesthesia.

摘要

Two experiments designed to study the effects of hypnotic suggestions on tactile sensitivity are reported. Experiment 1 utilized 40 subjects selected and classified into four groups according to their scores on the Stanford Scale of Hypnotic Susceptibility: Form C (SHSS:C). The effects of suggestions for anesthesia, as measured by both traditional psychophysical methods and signal detection procedures, were linearly related to hypnotic susceptibility. Experiment 2 employed the same methodologies in an application of the real-simulator paradigm, to examine the effects of suggestions for both anesthesia and hyperesthesia. A total of 19 undergraduate students were selected for their scores on the SHSS:C and classified into two groups: insusceptible simulators, who were given instructions to simulate the behavior of a highly hypnotizable person; and highly hypnotizable reals, who underwent a standard hypnotic procedure. Significant effects of hypnotic suggestion on both sensitivity and bias were found in the anesthesia condition, but not for the hyperesthesia condition. A new bias parameter, C', was derived which indicated that much of the bias found in the initial analyses was artifactual, a function of changes in sensitivity across conditions. There were no behavioral differences between reals and simulators in any of the conditions, though analyses of post-experimental interviews suggested the two groups had very different phenomenal experiences. Finally, a manipulation of response strategies induced different levels of sensitivity. The implications of these and other similar findings for signal detection theory are discussed in the context of implicit and explicit perception. Taken together, these results indicate that hypnotic suggestions can produce genuine decrements but not increments, in tactile sensitivity. The magnitude of these changes are partly a function of which perceptual system--the implicit or the explicit--is implicated in the assessment of sensitivity. Overall, these conclusions are consistent with 'neodissociation' accounts of hypnotic phenomena.