Hypnosis as a Method for Investigating Unconscious Thought Processes—A Review of Research

For some time, the value of hypnosis as a tool for scientific investigation was obscured by its dramatic therapeutic effects. Hypnosis played a critical role in revealing the relationship between unconscious thinking and neurotic symptoms by providing Freud with a microscope of the psyche to observe what was heretofore unobservable—the traumatic memories with their strange connections to symptoms. Unfortunately, as the limitations of the cathartic method became evident, hypnoanalysis was abandoned by Freud and with it interest was lost in using hypnosis as a method for investigating mental processes. Our historical review of studies involving hypnosis was organized around and focused attention on two points: the notable methodological advances and theoretical contributions that came out of the Breuer and Freud clinical innovation of listening to patients talk freely while in hypnosis, and what we delineated as a basic pattern or schema between apparently widely divergent and unrelated observations and studies, with particular emphasis on the mediating role of language.

Hypnosis may have been superseded as a therapy, but the advantages in using hypnosis as a research instrument remain. By examining in detail, as we have in this paper, the clinical observations and experiments using hypnosis through the years, one can better appreciate the striking role and unique part played by hypnosis in making available otherwise unknown relationships between such things as posthypnotic suggestion phenomena, dreams, symptom formation, and certain experimentally induced behavior. Without the purchase provided by hypnotically retrieved reminiscences, it is unlikely that the nature of unconscious