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.     

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.     

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.     

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.     

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.     

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.     

Changes in the sense of agency during hypnosis: The Hungarian version of the Sense of Agency Rating Scale (SOARS-HU) and its relationship with phenomenological aspects of consciousness

Changes in the sense of agency are defining feature of hypnosis. The Sense of Agency Rating Scale (SOARS) is a 10-item questionnaire, administered after a hypnosis session to assess alteration in the sense of agency. In the present study, a Hungarian version of the measure (SOARS-HU) is presented. The SOARS-HU and the Phenomenology of Consciousness Inventory (PCI) were administered to 197 subjects following hypnotizability screening with the Harvard Group Scale of Hypnotic Susceptibility Scale, Form A (HGSHS:A). Confirmatory factor analysis and correlations with hypnotizability demonstrate the reliability and validity of the SOARS-HU. Changes in the Involuntariness and Effortlessness subscales of the SOARS-HU were associated with alterations in subjective conscious experience, as measured by the PCI. These changes in subjective experience remained significant after controlling for HGSHS:A scores. These results indicate that changes in the sense of agency during hypnosis are associated with alterations of consciousness that are independent of hypnotizability.     

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.     

The relationship between different types of dissociation and psychosis-like experiences in a non-clinical sample

This study investigated whether detachment-type dissociation, compartmentalisation-type dissociation or absorption was most strongly associated with psychosis-like experiences in the general population. Healthy participants (N = 215) were tested with the Dissociative Experiences Scale (DES, for detachment-related dissociative experiences); the Harvard Group Scale of Hypnotic Susceptibility (HGSHS: A, for dissociative compartmentalisation); the Tellegen Absorption Scale (TAS, for non-clinical ‘functional’ dissociative experience); and two measures of psychotic-like experiences, the 21-item Peters et al. Delusions Inventory (PDI-21) and the Cardiff Anomalous Perceptions Scale (CAPS). In multiple regression analyses, DES and TAS but not HGSHS: A scores were found to be significantly associated with PDI-21 and CAPS overall scores. A post hoc hierarchical cluster analysis checking for cluster overlap between DES and CAPS items, and the TAS and CAPS items showed no overlap between items on the DES and CAPS and minimal overlap between TAS and CAPS items, suggesting the scales measure statistically distinct phenomena. These results show that detachment-type dissociation and absorption, but not compartmentalisation-type dissociation are significantly associated with psychosis-like experiences in a non-clinical population.     

Direct verbal suggestibility: Measurement and significance

Hypnotic suggestibility is part of the wider psychological trait of direct verbal suggestibility (DVS). Historically, DVS in hypnosis has informed theories of consciousness and of conversion disorder. More recently it has served as a research tool in cognitive science and in cognitive neuroscience in particular. Here we consider DVS as a general trait, its relation to other psychological characteristics and abilities, and to the origin and treatment of clinical conditions. We then outline the distribution of DVS in the population, its measurement, relationship to other forms of suggestibility, placebo responsiveness, personal characteristics, gender, neurological processes and other factors, such as expectancy. There is currently no scale specifically designed to measure DVS outside a hypnotic context. The most commonly used and well-researched of the hypnosis-based scales, the Harvard Group Scale, is described and identified as a basis for a more broadly based measure of DVS for use in psychological research.     

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.     

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.     

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.     

Some operationalizations of the neodissociation concept and their relationship to hypnotic susceptibility

We operationalized and tested E. R. Hilgard's (1973a, 1977b) neodissociation theory. His work suggested that the dissociation necessary for experiencing hypnotic phenomena may be attributable to a general capacity for dissociation that should be measurable outside of the domain of hypnosis. We used several types of operational definitions and tasks in order to capture a wide range of meanings. The performances of 169 undergraduates on clerical/motor and cognitive tasks in selective attention and divided attention conditions, as well as the degree of incidental learning, were correlated with scores on the Harvard Group Scale of Hypnotic Susceptibility. The results do not support a neodissociation theory despite the study's respectable convergent-discriminant validity. Although conceptual and methodological considerations were noted, the results may indicate an important limitation of the explanatory power of E. R. Hilgard's neodissociation theory.     

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.     

Modifying hypnotic suggestibility with the Carleton Skills Training program

The Carleton Skills Training (CST) program was used to investigate (a) whether increases in hypnotic responsiveness obtained at Carleton University could be replicated at a different laboratory, (b) the influence of demand characteristics on suggestibility gains, and (c) whether initial gains are maintained over time. After two screening sessions, a replication and experimental group received the CST program, while a control group was allowed to practice hypnotic responding. All groups were then tested twice. Whereas the replication group was told that training and testing were part of the same experiment, the experimental group was told that training and testing were unrelated. Trained subjects returned after 4 months for a final session. Results indicated that (a) the CST program does increase hypnotic responsiveness, (b) suggestibility gains found in this study were relatively modest, (c) demand characteristics may influence suggestibility gains, and (d) suggestibility gains were not maintained at follow-up.     

The interoception and imagination loop in hypnotic phenomena

We tested a working hypothesis that the ideomotor and motor-control suggestions measured by current hypnotizability scales depend on the activation of an interoception-imagination processing loop. In three experiments, participants were exposed to an induction phase, Items 3 (mosquito hallucination) and 8 (arm immobilization) of the Stanford Hypnotic Susceptibility Scale, Form C, and a new version of Item 8 involving the additional activation of imaginative and interoception processes. We found that this modified version of Item 8 elicited greater responsiveness to suggestion, irrespective of its position in the sequence of hypnotic items. We argue that this interoception-imagination loop hypothesis provides a useful information processing analysis for understanding several hypnotic phenomena.     

Imaginative suggestibility and hypnotizability: an empirical analysis.

Hypnotic and nonhypnotic suggestibility were investigated in 2 experiments. In Experiment 1, nonhypnotic suggestibility was suppressed when measured after hypnotic suggestibility, whereas hypnotic suggestibility was not affected by the order of assessment. Experiment 2 confirmed a small but significant effect of hypnosis on suggestibility when nonhypnotic suggestibility was measured first. Nonhypnotic suggestibility was correlated with absorption, fantasy proneness, motivation, and response expectancy, but only expectancy predicted suggestibility when the other variables were controlled. Behavioral response to hypnosis was predicted by nonhypnotic suggestibility, motivation, and expectancy in a model accounting for 53% of the variance. Experiential response to hypnotic suggestion was predicted only by nonhypnotic suggestibility. Unexpectedly, hypnosis was found to decrease suggestibility for a substantial minority of participants.     

A laboratory task for induction of mood states

One hundred female college students were administered the Harvard Group Scale of Hypnotic Susceptibility, Form A, to provide a measure of primary suggestibility. In a 2nd hr, each S was randomly assigned to one of five individual treatments of 20 Ss each. One group read and concentrated upon 60 self-referent statements intended to be elating: a second group read 60 statements intended to be depressing. A third group read 60 statements which were neither self-referent nor pertaining to mood. This group controlled for the effects of reading and experimental participation per se. Fourth and fifth groups received demand characteristics control treatments designed to produce simulated elation and simulated depression, respectively.

Two measures of pre-treatment mood level were obtained from each S at the beginning other individual treatment. Following treatment, as criteria for elation and depression, seven behavioral task measures were obtained. Four of these distinguished significantly among the treatment groups. The comparative performance of Ss in the three control groups indicated that the obtained mood changes could not be attributed to artifactual effects. Moreover, post-experimental questionnaire data strongly supported the conclusion that Elation and Depression treatments had indeed respectively induced elation and depression.     

Time to update our suggestibility scales

Oakley and colleagues (2021) suggest that a classic scale – HGSHS:A, aiming to measure hypnotic suggestibility – can be used to measure direct verbal suggestibility (DVS). According to the authors, DVS is a trait that can be measured both with and without hypnosis. I find this initiative highly welcome. However, I wish to give several examples why it is time to develop entirely new scales instead. Rather than trying to explain more phenomena with a single scale or concept, researchers should take a cue from research that points to a far more nuanced picture of suggestibility than a construct like DVS allows. There may be no single, unified phenomenon that can be measured with a single scale. The old, time-tested scales should be treated neither as sacred nor final. They require up-to-date, critical analysis of what exactly they measure, with an eye to how they can be further improved.