Individual Differences in Susceptibility to Hypnosis* by Ernest

While all investigators report wide individual differences in susceptibility to hypnosis, the form of the distribution is a matter of some uncertainty. Some years ago Hull' concluded that "susceptibility to hypnotic suggestion is fairly evenly distributed over the range from no susceptibility whatever to the most profound susceptibility." In a more recent review Weitzenhoffer2has shown a summary tendency toward a skewed distribution, a larger fraction of the subjects yielding scores of low susceptibility than of high susceptibility. There are occasional findings of bimodality, with scores in the middle range being fewer than those at the extremes.3 Because of these uncertainties it appeared desirable to repeat hypnotic susceptibility measures on a randomly selected population, and to determine the form of the distribution with more than one type of score. Subjects and Hypnotic Procedure.-The experimental subjects were 74 undergraduate students, 40 men and 34 women, from an introductory psychology course. They volunteered for an experiment on attention, reported elsewhere.4 At the end of this experiment they were invited to participate in an experiment involving hypnosis. Because 74 of the 78 subjects accepted the invitation, we believe that we have avoided most of the bias that would have resulted, had the students been asked in the first place to volunteer for an experiment on hypnosis. The procedure for inducing hypnosis followed closely that proposed by Friedlander and Sarbin.5 The subject was introduced to suggestion by experiencing the waking suggestion of falling backward from a standing position. The hypnotic procedure proper then followed. Seated in a comfortable upholstered armchair, he gazed upward at a small bright object (thumbtack) on the ceiling and received suggestions of relaxation and eye closure. After the eyes were closed (either through accepting the suggestion or by direct instruction), a number of acts were suggested, each followed by a challenge, e. g., "Your eyes are tightly shut. You cannot open them. Try to open them." By scoring successes and failures on the various performances, a score of susceptibility to hypnosis can be computed. The scoring scales used are indicated in Table 1.6