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.     

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.     

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 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.     

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.     

Personality types and hetero- versus auto-hypnosis

The Multivariate Personality Inventory (MPI; Magaro & Smith, 1981), the Harvard Group Scale of Hypnotic Susceptibility (HGSHS; Shor & Orne, 1962), and the Inventory of Self-Hypnosis (ISH; Shor, 1970) were used to investigate the relationship between personality style and hypnotic procedure in the determination of hypnotic susceptibility. On the basis of MPI scores, a normal college population was segregated into 5 personality styles: hysteric, manic, depressive, character disorder, and compulsive. The hysteric personality was found significantly more hypnotizable than the other personality types in the HGSHS induction context, whereas the compulsive personality was found significantly more hypnotizable in the ISH induction context. Results are discussed in terms of personality and situational factors in relation to previous hypnotic susceptibility research.     

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.     

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.     

Impulsivity,self-control,and hypnotic suggestibility

Hypnotic responding might be due to attenuated frontal lobe functioning after the hypnotic induction. Little is known about whether personality traits linked with frontal functioning are associated with responsiveness to hypnotic suggestions. We assessed whether hypnotic suggestibility is related to the traits of self-control and impulsivity in 154 participants who completed the Brief Self-Control Scale, the Self-Regulation Scale, the Barratt Impulsiveness Scale (BIS-11), and the Harvard Group Scale of Hypnotic Susceptibility (HGSHS:A). BIS-11 non-planning impulsivity correlated positively with HGSHS:A (Bonferroni-corrected). Furthermore, in the best model emerging from a stepwise multiple regression, both non-planning impulsivity and self-control positively predicted hypnotic suggestibility, and there was an interaction of BIS-11 motor impulsivity with gender. For men only, motor impulsivity tended to predict hypnotic suggestibility. Hypnotic suggestibility is associated with personality traits linked with frontal functioning, and hypnotic responding in men and women might differ.     

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.     

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.     

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.     

A social-cognitive skills approach to the successful modification of hypnotic susceptibility

Subjects low and medium in hypnotic susceptibility were administered cognitive strategy and instructional set information and also practiced responding to test suggestions in order to enhance susceptibility. Those in one modification treatment received this information both from the experimenter and by observing a videotaped female model who responded successfully to suggestions and reported on the cognitive strategies she used to do so. Those in a second modification treatment received the information and practice but were not exposed to the model. Low and medium susceptibles in a third condition (practice alone) received a hypnotic induction procedure and practice suggestions but neither modification information nor modeling. No-treatment controls performed a filler task. All subjects were posttested on two different susceptibility scales. Information plus modeling produced significantly greater increments on all objective and subjective indices of susceptibility on both posttests than did practice-alone or control treatments. Susceptibility increments in the information without model treatment always fell between those of the model and practice-alone treatments. In the modeling treatment, over half of the initial low susceptibles and over two thirds of the initial medium susceptibles scored as high susceptibles on both posttests. These findings provide strong support for a social-cognitive skill formulation of hypnotic susceptibility.     

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.     

Personality and differential susceptibility to hypnosis: further replication and sex differences.

Following the study of Gibson & Curran (1974), a further sample of 45 subjects were tested on the Eysenck Personality Inventory (EPI) and a slightly modified form of the Stanford Hypnotic Susceptibility Scale (SHSS) in precisely the same way. The results in this second sample were broadly the same as those obtained in the earlier study. Combining the two samples, it was found that the sex variable provided some interesting contrasts. The power of the lie scale of the EPI to predict hypnotic susceptibility observed earlier was found to be a significant effect only for males. While there was no significant difference between the sexes in terms of the means and S.D.S. of the extraversion (E) and neuroticism (N) scales, when the interaction of these scales was studied males and females differed significantly. The population from the two studies (n = 88) was analysed by means of polar coordinates in the manner suggested by Eysenck (1966) with regard to the E nad N scales. Esyenck's prediction as to hypnotic susceptibility was strikingly confirmed. These data are briefly discussed in terms of alternative approaches to hypnosis from the 'state' and the 'non-state' viewpoints.     

Interactions of afterimages for orientation and color: experimental data and model simulations

Sequential viewing of two orthogonally related patterns produces an afterimage of the first pattern. We report an experiment that quantifies some properties of this type of afterimage. It is shown that it is important for the two patterns to have orthogonal orientations and that the appearance of the afterimage does not depend on the spatial frequency of the second pattern. We then show that Grossberg's model of interacting boundary and feature contour systems can account for the observed properties of these afterimages.     

Hypnotic susceptibility and the perception of afterimages and dot stimuli

Three experiments were conducted to determine the relationship between hypnotic susceptibility level and the susceptibility to several perceptual phenomena. Experiment I required subjects to observe an induced afterimage in a light-proofed environment and to report the frequency of direction and color changes. In addition, subjects reported the persistence of the afterimage. Experiment II involved the observation of a black dot against a white background, with frequency of observed movement being the dependent measure. Experiment III was similar to the second experiment except that the stimulus was encompassed by a frame. In Experiments I and II, subjects judged high in hypnotic susceptibility reported perceiving the strongest effect. This phenomenon was virtually eliminated in the third experiment. These results were interpreted as supporting a process whereby subjects judged high in hypnotic susceptibility are better able to selectively attend to relevant cues in a stimulus array during conditions of perceptual impoverishment.     

Developmental Experiments in Hypnosis

Two-hundred-forty children, including ten boys and girls at each year level from five through sixteen, were selected from the entire public school population of a small city for testing on the Children's Hypnotic Susceptibility Scale. For most of these children, testing was repeated yearly for the next two years. Reliability for the Children's Scale was quite satisfactory for individual prediction. There were absolutely no differences in the hypnotic susceptibility of boys and girls in this sample. Intelligence had only low positive correlations with susceptibility. The correlation of age with susceptibility, measured either cross-sectionally or longitudinally, is positive and significant, but small. Changes in individual performance over time are generally minimal, and hypnotic susceptibility may be considered a relatively stable component of personality structure.