Artifact in the "essence of hypnosis": an evaluation of trance logic.

In Phase I of the investigation, 70 5s were assigned to one of three treatment conditions: hypnotic induction, instructions to simulate hypnosis, or imagination control. All 5s were assessed on Orne's two indexes of trance logic (the transparent hallucination and the double hallucination). The imagination controls consistently showed trance logic as often as the hypnotic Ss. Depending upon the stringency of the criterion for hallucination, the simulating 5s showed trance logic less often, as often, or more often than the hypnotic 5s and the imagination controls. In Phase II of the investigation, simulating 5s consistently manifested trance logic as often as highly selected "somnambulistic" hypnotic 5s. Since trance logic was not found to be a discriminating characteristic of hypnotic 5s, investigators who seek the "essence of hypnosis" must now search elsewhere.