Moderating influences of hypnotic susceptibility on signal-detection task performance

This study investigated the differential influence of hypnotic susceptibility level on signal detection task (SDT) performance in waking and hypnotic conditions. As assessed by the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS: A) and the Stanford Hypnotic Susceptibility Scale, Form C (SHSS: C), 20 high (9–12), 20 medium (4–8), and 20 low (0–3) hypnotizables participated. In counterbalanced conditions of waking and hypnosis, Ss (Subjects) were given 36 signal detection trials, consisting of 12 strong signals, 12 weak signals, and 12 “no” signals. No differences were observed in the waking condition between low, medium, and high hypnotizables on strong and weak signal trials. In hypnosis, high hypnotizables exhibited significantly superior performance on the strong signal trials in comparison with low hypotizables, and performed significantly better on the weak signal trials than did the low and medium hypnotizables. Low and medium hypnotizables performed similarly in waking and hypnotic conditions, while high hypnotizables showed significant enhancements in performance for strong and weak signal trials during hypnosis. This research was supported, in part, by a grant from Fort Hays State University.     

Lack of correlation between hypnotic susceptibility and various components of attention

The purpose of our study was to measure the relationship between performance on various attentional tasks and hypnotic susceptibility. Healthy volunteers (N = 116) participated in a study, where they had to perform several tasks measuring various attention components in a waking state: sustained attention, selective or focused attention, divided attention and executive attention in task switching. Hypnotic susceptibility was measured in a separate setting by the Waterloo-Stanford Groups Scale of Hypnotic Susceptibility, Form C (WSGC).We found no significant correlation between any of the attentional measures and hypnotic susceptibility. Highly hypnotizables did not prove to be superior to or worse than the other individuals in any of the tests.These results do not support the neuropsychophysiological model of hypnosis, as they show no consistent relationship between hypnotic susceptibility and waking attentional performance.     

Individual differences in afterimage persistence: relationships to hypnotic susceptibility and visuospatial skills.

To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images.     

Eidetic-like imagery in hypnosis: rare but there

The production of eidetic-like imagery during hypnosis in subjects with high but not low hypnotizability was supported in three separate experiments using nonfakable stereograms (Julesz, 1971; Gummerman, Gray, & Wilson, 1972). In Experiment 1, 6 (25%) of 24 stringently chosen, high hypnotizables were able to perceive one of the superimposed stereograms (presented monocularly) during conditions of standard hypnosis or hypnotic age regression, or under both conditions, but not during waking. In Experiments 2 and 3, low and high hypnotizables were presented stereograms in an alternating, monocular fashion (one-half to each eye). In Experiment 2, 10% of the high hypnotizables perceived one or more stereograms in hypnosis or age regression, but not during waking. In Experiment 3, none of the 17 low hypnotizables reported correct stereograms, but 6 of the 23 high hypnotizables (26%) did. Relationships between imagery performance and visuo-spatial abilities were investigated. Results support the general hypothesis that hypnosis enhances imaginal processing of information to be remembered that is a literal or untransformed representation.     

Effects of active alert and relaxation hypnotic inductions on cold pressor pain

We contrasted relaxation and active alert hypnotic inductions with or without a specific suggestion for cold pressor pain analgesia. Groups of high (n = 38) and low (n = 27) hypnotizable subjects were tested; hypnotizability had been determined from results of the Stanford Hypnotic Susceptibility Scale, Form C. Cold pressor pain data were obtained after counterbalanced exposure to relaxation and active alert inductions. Highly hypnotizable subjects demonstrated lower pain scores than did low hypnotizable ones. Pain reports did not differ between induction conditions. Highly hypnotizable subjects given an analgesic suggestion showed lower pain scores than did those exposed only to hypnosis. The findings, conceptualized within E.R. Hilgard's (1977a) neodissociation theory, show that relaxation is not necessary for hypnotic analgesia.     

Hypnotic suggestibility,cognitive inhibition,and dissociation

We examined two potential correlates of hypnotic suggestibility: dissociation and cognitive inhibition. Dissociation is the foundation of two of the major theories of hypnosis and other theories commonly postulate that hypnotic responding is a result of attentional abilities (including inhibition). Participants were administered the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C. Under the guise of an unrelated study, 180 of these participants also completed: a version of the Dissociative Experiences Scale that is normally distributed in non-clinical populations; a latent inhibition task, a spatial negative priming task, and a memory task designed to measure negative priming. The data ruled out even moderate correlations between hypnotic suggestibility and all the measures of dissociation and cognitive inhibition overall, though they also indicated gender differences. The results are a challenge for existing theories of hypnosis.     

Not all group hypnotic suggestibility scales are created equal: individual differences in behavioral and subjective responses

To examine the influence of hypnotic suggestibility testing as a source of individual differences in hypnotic responsiveness, we compared behavioral and subjective responses on three scales of hypnotic suggestibility: The Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS: A; Shor, R. E., Orne, E. C. (1962). Harvard Group Scale of Hypnotic Susceptibility. Berlin: Consulting Psychologists Press); the Carleton University Responsiveness to Suggestion Scale (CURSS; Spanos, N. P., Radtke, H. L., Hodgins, D. C., Stam, H. J., Bertrand, L. D. (1983b). The Carleton University Responsiveness to Suggestion Scale: Normative data and psychometric properties. Psychological Reports, 53, 523-535); and the Group Scale of Hypnotic Ability (GSHA; Hawkins, R., Wenzel, L. (1999). The Group Scale of Hypnotic Ability and response booklet. Australian Journal of Clinical and Experimental Hypnosis, 27, 20-31). Behavioral and subjective responses to the CURSS were significantly different than those on the HGSHS: A and GSHA. More participants were classified as "low suggestible" on the CURSS and they reported subjective experiences more similar to everyday mentation. Attitudes and expectancies of participants who received the GSHA were less predictive of responding, but rates of responding and subjective experiences were similar on the GSHA and the HGSHS: A. Discussion focuses on implications for the use of group hypnotic suggestibility scales.     

Hypnotic susceptibility and its relationship to outcome in the behavioral treatment of asthma: some preliminary data

12 subjects from an experiment on relaxation therapy for asthma were given the Harvard Group Scale of Hypnotic Susceptibility, Form A. Full scale hypnotic susceptibility scores were positively correlated, at a borderline significance, with improvement in the methacholine challenge test, a measure of asthma severity. Performance on the amnesia item of the Harvard Group Scale was correlated with improvement in self-reported symptoms of asthma.     

Dimensions of hypnotic depth: an exploratory study

Hypnotic depth, hypnotic susceptibility, and the relationship between the two were studied in two separate samples. In the first study, 45 aubjects were tested on the Creative Imagination Scale (CIS) and the induction part (i.e. the eye closure item) of the Stanford Hypnotic Susceptibility Scale, Form A (SHSS:A). Retrospective depth reports were taken, and hypnotic responsiveness scores on the CIS was assessed. The results demonstrated significantly higher depth scores for the SHSS:A (eye closure) than for the CIS. Moreover, there was a significant correlation between hypnotic susceptibility and depth score on the CIS. In the second study, 19 subjects were again tested on the CIS and the eye closure item of the SHSS:A. As in the first study, spontaneous depth estimates were elicited. In addition, the subjects were required to estimate their experiences retrospectively according to three distinct operationalizations of hypnotic depth, i.e. depth in terms of bodily relaxation, absorption, and dissociation. Analysis of variance revealed a highly significant effect for depth measures, and a significant depth measure by hypnosis method interaction effect. Hypnotic depth defined as bodily relaxation produced the highest score, followed by absorption. The mean scores were lowest for spontaneous depth and dissociation. Again, significant correlations between susceptibility and depth reports were found.     

Hypnotic deafness: a psychophysical study of responses to tone intensity as modified by hypnosis.

Hypnotic deafness was suggested for 1000 Hz tones presented in random orders at seven intensities between 17 and 70 db. Subjects were 70 college students stratified into four levels of hypnotic susceptibility, ranging from low to high. Four conditions were presented within a single session. Two conditions tested normal hearing, one in waking and one in hypnosis; two tested reported loudness of the tones as reduced by hypnotic suggestion. The method of magnitude estimation was employed. Hearing reduction was found to correlate .59 with hypnotic susceptibility in the total sample. Few high hypnotizables reduced their hearing to zero; their mean residual hearing during the deafness conditions was 55% of normal. Power functions for the relationship between tone intensity and magnitude estimates for conditions of normal hearing and deafness were found to be relatively parallel and orderly, differing primarily in intercept value. Order effect anomalies are discussed. The "hidden observer" method showed that for 4 of the 70 subjects the covert hearing was found to be at least 20% greater than that reported overtly within hypnotic deafness and approached normal hearing. As in our previous hypnotic analgesia research, not all subjects who reduced their hearing significantly gave subsequent covert reports which differed from reported overt hearing. Discussion is given for evidence of two levels of information processing during hypnotically suggested perceptual distortions.     

Distignuishing the source of memories reported during prior waking and hypnotic recall attempts

Subjects attempted to identify the occasion on which they first reported particular responses to questions that were asked twice during an experiment on hyphosis and memory 1 week earlier. During this earlier experiment, subjects of high and low hypnotizability had been randomly allocatd to one of two recall test sequences: wake-hypnosis ro wake-wake. Recall improved from the first (R1) to the second test (R2) in a comparable manner for both test sequences, indicating a failure of hypnosis to enhance memory. It is noteworthy that, when later queried about the origins of specific recollections, the majority of subjects exhibited a bias to attribute their responses to R1, regardless of whether hypnosis was used during R2. Moreover, low hypnotizables exposed to the hypnotic procedure and, to a lesser extent, high hypnotizables who recalled both times in the waking condition displayed and exaggerated tendency to overattribute recollections to R1. These data indicate that individuals cannot distinguish between memories retrieved prior to hypnosis and those that occured during hypnosis. Implications for implementing judicial standards regarding hypnosis are discussed.     

The role of expectation and memory‐retrieval techniques in the construction of beliefs about past events

This study assessed social factors affecting the elicitation of false reports for events occurring the day after birth. High, medium and low hypnotizable participants (N=170) were randomly assigned to hypnotic, guided imagery (non‐hypnotic), expectancy or control conditions. Participants were led to believe that they had experienced a specific event on the day after birth. Hypnotic and guided imagery participants were age regressed, while participants in the expectancy condition were provided with cues suggesting access to this memory was feasible. Relative to controls, these participants recalled higher levels of day‐after‐birth reports, although age‐regressed participants reported significantly more event specific details than expectancy participants. Furthermore, high and medium hypnotizables were more likely than low hypnotizables to recall events occurring the day after birth. Implications of this study within the therapeutic setting are discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Hypnosis,hypnotic suggestibility,memory, and involvement in films

Our research extends studies that have examined the relation between hypnotic suggestibility and experiential involvement and the role of an hypnotic induction in enhancing experiential involvement (e.g., absorption) in engaging tasks. Researchers have reported increased involvement in reading (Baum & Lynn, 1981) and music-listening (Snodgrass & Lynn, 1989) tasks during hypnosis. We predicted a similar effect for film viewing: greater experiential involvement in an emotional (The Champ) versus a non-emotional (Scenes of Toronto) film. We tested 121 participants who completed measures of absorption and trait dissociation and the Harvard Group Scale of Hypnotic Susceptibility and then viewed the two films after either an hypnotic induction or a non-hypnotic task (i.e., anagrams). Experiential involvement varied as a function of hypnotic suggestibility and film clip. Highly suggestible participants reported more state depersonalization than less suggestible participants, and depersonalization was associated with negative affect; however, we observed no significant correlation between hypnotic suggestibility and trait dissociation. Although hypnosis had no effect on memory commission or omission errors, contrary to the hypothesis that hypnosis facilitates absorption in emotionally engaging tasks, the emotional film was associated with more commission and omission errors compared with the non-emotional film.     

Enhancing hypnotic susceptibility: interpersonal and rapport factors

This research supported the hypothesis that hypnosis can be thought of as a set of potentially modifiable social-cognitive skills and attitudes. A low-interpersonal-training treatment devised by Gorassini and Spanos (1986) was compared with a treatment designed to modify not only cognitive factors but also to augment rapport with the trainer and diminish resistance to responding (high-interpersonal training). Fifty percent of the initially unhypnotizable subjects in the high-interpersonal condition tested as being highly susceptible to hypnosis (high susceptibles) at posttest on the Harvard Group Scale of Hypnotic Susceptibility (Shor & Orne, 1962); 25% of the unhypnotizable subjects in the low-interpersonal condition responded comparably. Eighty-three percent of the medium-susceptibility (medium susceptibles) subjects tested as being highly susceptible at posttest in both conditions. Practice-alone control subjects' performance was stable across testings. The study was the first to demonstrate that treatment gains generalize to a battery of novel, demanding suggestions (generalization index) that have been found to differentiate highly susceptible subjects from unhypnotizable simulating subjects. The importance of rapport was evidenced by the finding that rapport ratings paralleled group differences in hypnotic responding and that rapport correlated substantially with susceptibility scores at posttest and with the generalization index. Whereas initial hypnotizability scores correlated significantly with retest susceptibility scores, initial hypnotizability failed to correlate significantly with the generalization index.     

Transient positive and negative experiences accompanying stage hypnosis.

Frequency of positive and negative experiences accompanying stage hypnosis was assessed in follow-up interviews with 22 participants of university-sponsored performances. Most subjects described their experience positively (relaxing, interesting, exciting, satisfying, illuminating, and pleasurable), but some described it negatively (confusing, silly, annoying, and frightening). Five subjects (22.7%) reported partial or complete amnesia; all were highly responsive to the stage hypnosis suggestions. One subject was completely unable to breach amnesia and felt annoyed and frightened. Five subjects (22.7%) believed the hypnotist had control over their behavior. Participants (n = 15) tested subsequently on the Stanford Hypnotic Susceptibility Scale, Form C (Weitzenhoffer & Hilgard, 1962) were mostly moderately to highly hypnotizable (M = 7.07), and the scores correlated significantly (r = .68) with the percentage of passed stage hypnosis suggestions.     

Effects of suggestibility and hypnosis on accurate and distorted retrieval from memory

Research investigated the hypothesis inferred from the theorizing of Loftus that suggestibility is related to the tendency to incorporate incorrect information into memory when this information has been subtly introduced after the to-be-remembered events have occurred. Specifically, it was predicted that if level of suggestibility is theoretically relevant to subjects' acceptance of misleading information, then more subjects who are highly hypnotically suggestible than those with a low level of hypnotic suggestibility will incorporate the incorrect information into memory. Hypnotic as compared with waking instruction should enhance this distortion effect by providing a context of testing in which subjects are readily prone to respond positively to suggestions. Eight independent groups of 12 subjects were tested. Separate groups of subjects of high and low suggestibility were presented with misleading or neutral information about a wallet-snatching incident and tested for memory under either waking or hypnotic instruction. Analysis of subjects' memory distortions indicated that suggestibility plays a somewhat different role than has been argued previously. The magnitude of distortion that was observed varied according to the stimulus features that were studied, but hypnotic suggestibility was not associated with the distortion effect. Despite the fact that hypnosis did not enhance recall in any way, subjects were frequently confident that distorted memories recovered under hypnosis were accurate.     

Sustained attentional and disattentional abilities and arousability: Factor analysis and relationships to hypnotic susceptibility

The neurophysiologically separate dimensions of deeply focused, sustained attention and arousability are shown to be differentially related to hypnotic susceptibility. University undergraduates, 98 men and 112 women, were administered the Harvard Group Scale of Hypnotic Susceptibility; the Group Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C); and questionnaires that assessed attentional abilities (Differential Attentional Processes Inventory (DAPI), Tellegen Absorption Scale (TAS)), Extraversion (Eysenck Personality Questionnaire), strength of the nervous system (Strelau Temperament Scale (STS)), augmenting-reducing (Vando Reducer-Augmenter Scale (RAS)), and emotionality (Affect Intensity Measure (AIM)). Women were significantly higher on TAS, DAPI dual attention physical-cognitive scale, and AIM; men were significantly higher on TAS and STI Strength of Excitation Scale. Separate factor analyses for men and women separately yielded fairly similar four-factor solutions. The first major factor, defined by DAPI Moderately Focused Attention and Dual Attention scales, represented moderately sustained attention in a complex environment with limited interference from competing stimuli. The extremely involved and focused attention factor, defined by the TAS and DAPI Extremely Focused Attention Scale, had hypnotic susceptibility loaded more strongly for men than women. The arousability factor was defined by EPQ Extraversion, STI Mobility of Nervous System (MNS) scale, and RAS. The neo-Pavlovian nervous system processes factor was defined by the STI Strength of Excitation and Strength of Inhibition scales; the STI MNS scale also loaded on this factor for men. Only for women were introverts more hypnotizable than extraverts. Results support H. J. Crawford and J. H. Gruzelier's (1992) in E. Fromm and M. Nash (Eds.) Contemporary Perspectives in Hypnosis Research (pp. 227–266) New York: Guildford Press) neurophysiological model of hypnosis that proposes that highly hypnotizable persons have a more efficient fronto-limbic sustained attentional and disattentional system.     

Hypnotic susceptibility and familial handedness

The possible relationship between hypnotic susceptibility and familiar handedness was examined. In a mass-testing session of students enrolled in introductory psychology classes, subjects were administered the Harvard Group Scale of Hypnotic Susceptibility, Form A and were also required to complete a questionnaire that ascertained information on their dominant handedness and that of their immediate family relatives. Subjects who had immediate sinistral relatives scored significantly lower in hypnotic susceptibility compared to those who had a history of familial dextrality. When immediate relatives of the original subject pool were tested on hypnotic susceptibility level, sinistral relatives scored lower in susceptibility than dextral relatives. This may indicate the existence of a familial component in hypnotic susceptibility.     

Validation of a TAI Short Form with an Adolescent Sample

Subjects who pretested high or low in hypnotic suggestibility took a creativity test either under hypnosis or in a waking state. All subjects made a global estimate of their general degree of creativity. Greater figural-spatial creativity was exhibited in the hypnosis condition than in the waking condition by both high and low suggestibles. Creativity self-reports were not corroborated by actual creative performance.     

Artifact in the hypnosis-creativity relationship

Subjects who pretested high or low in hypnotic suggestibility took a creativity test either under hypnosis or in a waking state. All subjects made a global estimate of their general degree of creativity. Greater figural-spatial creativity was exhibited in the hypnosis condition than in the waking condition by both high and low suggestibles. Creativity self-reports were not corroborated by actual creative performance.