An experimental study of the effect of hypnosis on recall

The present study was undertaken in order to investigate the evidence available in the literature dealing with the effect of hypnosis on recall, and to conduct an experiment testing the hypothesis that there is hypnotic hypermnesia for recently learned meaningful material. In the literature there is a considerable amount of experimental evidence which shows rather conclusively that hypnosis facilitates the recall of long-forgotten memory material. However, there is relatively little evidence on the recall of recently learned material; and nearly all of this indicates that hypnosis confers no benefit on such recall. As White, Fox, and Harris have pointed out, though, those experiments showing negative results were conducted with nonsense material, and those indicating positive results (experiments with long-forgotten material) were carried out with meaningful material. In the present experiment testing the hypothesis of hypnotic hypermnesia for recently learned meaningful material, each of twelve subjects was given selected material to study. Each was then tested over this material, and approximately a month later, during which time the subject apparently refrained from relearning the subject matter, he was administered the same tests again. This time the tests were taken twice—once in the waking state and once in the trance state, and the results compared. Each subject performed on two different tests, thereby allowing twenty-four trance-waking recall comparisons. If a subject took a test first in the trance state--followed by the waking administration; then his second test was taken first in the waking state - -followed by the trance administration. Upon analysis of the data, it was found that the differences resulting from the trance-waking recall comparisons had extremely low critical ratios—too low to be considered in any way significant. So far as the results of this experiment are concerned, then, the indication is definitely against the hypothesis that hypnosis aids the recall of recently learned meaningful material.