Reponsiveness to Suggestions Following Waking and Imagination

I& of Abnormal Psychology 1966, Vol. 71, No. 3. 196-208 0 RESPONSIVENESS TO SUGGESTIONS FOLLOWING WAKING AND IMAGINATION INSTRUCTIONS AND FOLLOWING INDUCTION OF HYPNOSIS ' ERNEST R. HILGARD AND CHARLES T. TART2 Stanford University 2 experiments are reported to test the increase of responsiveness to suggestion tests following hypnotic induction over responsiveness to such tests in waking and imagination conditions, an increase that has been doubted as a result of experiments by Barber and Calverley (1962, 1963). In the 1st experiment, 60 Ss were divided into groups of 20 Ss each serving under 1 of 3 conditions in a 1st session (waking, imagination, hypnosis). All received a standard hypnotic induction in a 2nd session. While the treatment effects did not yield significant differences on the 1st day, there were significant gains in responsiveness to suggestions by the waking and imagination groups in the 2nd session. In the 2nd experiment, with some methodological improvements, 90 Ss served in 6 groups of 15 Ss each, in imagination without expectation of hypnosis, imagination with expectation of hypnosis, and hypnotic induction, in various combina- tions. Significant gains were found with hypnotic induction throughout. State reports (subjective responses of drifting into hypnosis) showed that those Ss withii both imagination and hypnotic induction conditions who reported them- selves as becoming hypnotized were the ones who yielded the highest suggestibility scores. The difficulty of obtaining significant treatment effects is noted unless Ss serve as their own controls. Increase in suggestibility has so long been to suggestions in the waking state and follow- associated with hypnosis that such increase ing hypnotic induction, two facts stand out: has commonly been considered to be a defin- 1. There is a substantial positive correla- ing characteristic of hypnosis. Thus the titles tion between responsiveness within the wak- of standard books reflect this intimacy being state and following hypnotic induction. tween hypnosis and suggestibility, for exam- This implies that responsiveness to sugges- ple, Hypnosis and suggestibility (Hull, 1933), tions carries within it a heavy loading of indi- Hypnotism: An objective study in suggesti- vidual differences common to both the waking bility (Weitzenhoffer, 1953). It is well-known, and hypnotic states. ' however, that responses to suggestions of the 2. The increase in responsiveness to sug- kind given within hypnosis may be obtained gestions over the waking state engendered by outside the hypnotic state; such suggestions a prior hypnotic induction is usually found are often called waking suggestions, a term to be significant, but the gain is typically of convenience that can be used without small "probably far less than the classical implying that hypnosis is a sleep state. When hypnotists would have supposed had the comparisons are made between responsiveness question ever occurred to them [Hull, 1933, =The investigation was carried out in the Labora- p. 2981 ." Hull's conclusions of a significant tory of Hypnosis Research, Department of Psy- but small gain following hypnotic induction chology, Stanford University, with the aid of a have been verified by Weitzenhoffer and Sjo- grant from the National Institute of Mental HeaIth, berg (1961) and by Barber and Glass (1962). Public Health Service (Grant MH-03859). Grateful acknowledgement is made of the assistance of the The second of these summary conclusions staff and research assistants in the Laboratory for has been challenged by Barber and Calverley their aid in the conduct of the experiments reported. (1962, 1963) on the grounds that the gains At the time C. T. Tart was holding a Public Health Service Postdoctoral Research Fellowship (1-F2-MH- in suggestibility found experimentally are to 14,622-01). be attributed to circumstances of experimen- 2 Now at the University of Virginia. tation, such as aroused task motivation, YD CHARLEST. TART rather than to the hypnotic state as such. 1. The variability in responses to hypnotic When they aroused task motivation in both suggestions from one subject to another is the waking state and the hypnotic state, dif- very great, the distributions are often flat, ferences between the two states became mini- sometimes 'bimodal, with extreme scores at mized or disappeared altogether. Their con- both ends of the scale (Hilgard, Weitzen- clusions rest upon an assumed equation of the hoffer, Landes, & Moore, 1961). Under these task motivations aroused under the two con- circumstances two risks are taken in compari- ditions. Unfortunately, their instructions dif- sons between small groups: First, that fered in important respects between their genuine differences may be obscured because waking groups and their hypnotic groups. In they are small and the variability great; addition, by contrast with the earlier Barber second, that obtained differences, meeting and Glass (1962) experiment, they no longer conventional statistical standards of signifi- used subjects as their own controls, so that cance, may arise when assignment is random other differences, besides the added task through the chance appearance in small groups motivation, occur between the experiments. of disproportionate numbers of extremely There are important methodological con- high-scoring or extremely low-scoring subjects. siderations that arise when two experimental 2. The nature of responsiveness to hyp- conditions are to be compared, when (a) re- nosis is such that within a random sample sponses between the two sets of conditions there will aDtxar a substantial number of are highly correlated, and (6) when the essentially nidsusceptible subjects, perhaps as expected differences are small. If the pre- many as two thirds of the group. Such sub- ferred hypothesis calls for no difference, this jects will dilute any comparison between result is more likely to emerge if group com- randomly selected groups assigned to waking parisons are made, and the correlation term and hypnotic conditions. Because they are neglected, as in the Barber and Calverley relatively insusceptible, gains between waking studies. If one seeks to detect any difference, and hypnosis are not to be expected; because however small, then the subject is likely to they for the most part extremely low be used as his own control, to take advantage scores they will contribute to low means and @ of the correlational term. The considerations high variability relative to the mean, thus are not entirely statistical ones, however, but reducing the probability of significant differ- depend on the appropriateness of what is ences between the compared groups. done to the actual relationships being studied. 3. At the other end of the scale, a few Because these problems are peculiarly dif- subjects with very high scores enter hypnosis ficult within hypnosis, some additional com- spontaneously withour a prior hypnotic in- ments are in order before proceeding to a duction, and for them also the changes from description of the current experiments. waking to hypnosis will be slight or absent. There are good reasons for not using sub- Because their scores are high, they also in- jects as their own controls within hypnotic crease the variability that reduces the signifi- experiments, particularly because of tenden- cance of differences between means. cies, whether deliberate or unconscious, for As a consequence, in group comparisons, subjects to modify their behavior under con- the weight must be carried bv those few trol conditions when they know that a hyp- subjectsvwho make substantial gains between notic session is to follow (Zamansky, Scharf, waking and hypnosis. An overall compari- & Brightbill, 1964). There is no assurance, son between two groups that does not take however, that expectations are circumvented into account the correlation between waking by having only one condition per subject responsiveness and hypnotic responsiveness either, if a subject knows that other subjects will understate the gains that take place for are being hypnotized. Failure to use subjects some subjects. as their own controls greatly attenuates the In view of these considerations. the experi- possibility of finding differences under two ments to be reported have been carried out conditions of experimentation. This follows in such a manner as to reveal some of the because : finer grain of the changes that take place RESPONSIVENESS between waking and hypnotic conditions, and Today you will be given tests of imagination the consequenc& of alternative treatments of under normal conditions. You will not be hypnotized. The better you can imagine, the more you'll the data. To this end, the instructions fol- respond; try as hard as you can to concentrate lowed are essentially those of Barber and and to imagine that the things I tell you are true. Glass (1962)) rather than the task-motiva- It may be noted that a deliberate effort was made tion instructions of Barber and Calverley to keep the waking subjects from drifting into hyp- (1962, 1963). It is conjectured that the nosis; while the imagination subjects were told that Barber and Calverley results do not require they would not be hypnotized, nothing was said the task-motivation interpretation at all; about spontaneous hypnosis. In order to control the drift into hypnosis in the that is, had the Barber and Glass subjects waking condition, and to assess the extent to which not served as their own controls, significant the subject became spontaneously

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