Differential patterns of spontaneous experiential response to a hypnotic induction: A latent profile analysis

A hypnotic induction produces different patterns of spontaneous experiences across individuals. The magnitude and characteristics of these responses covary moderately with hypnotic suggestibility, but also differ within levels of hypnotic suggestibility. This study sought to identify discrete phenomenological profiles in response to a hypnotic induction and assess whether experiential variability among highly suggestible individuals matches the phenomenological profiles predicted by dissociative typological models of high hypnotic suggestibility. Phenomenological state scores indexed in reference to a resting epoch during hypnosis were submitted to a latent profile analysis. The profiles in the derived four-class solution differed in multiple experiential dimensions and hypnotic suggestibility. Highly suggestible individuals were distributed across two classes that exhibited response patterns suggesting an inward attention subtype and a dissociative subtype. These results provide support for dissociative typological models of high hypnotic suggestibility and indicate that highly suggestible individuals do not display a uniform response to a hypnotic induction.     

Discrete response patterns in the upper range of hypnotic suggestibility: A latent profile analysis

High hypnotic suggestibility is a heterogeneous condition and there is accumulating evidence that highly suggestible individuals may be comprised of discrete subtypes with dissimilar cognitive and phenomenological profiles. This study applied latent profile analysis to response patterns on a diverse battery of difficult hypnotic suggestions in a sample of individuals in the upper range of hypnotic suggestibility. Comparisons among models indicated that a four-class model was optimal. One class was comprised of very highly suggestible (virtuoso) participants, two classes included highly suggestible participants who were alternately more responsive to inhibitory cognitive suggestions or posthypnotic amnesia suggestions, and the fourth class consisted primarily of medium suggestible participants. These results indicate that there are discrete response profiles in high hypnotic suggestibility. They further provide a number of insights regarding the optimization of hypnotic suggestibility measurement and have implications for the instrumental use of hypnosis for the modeling of different psychological conditions.     

Dissociated control as a signature of typological variability in high hypnotic suggestibility

This study tested the prediction that dissociative tendencies modulate the impact of a hypnotic induction on cognitive control in different subtypes of highly suggestible individuals. Low suggestible (LS), low dissociative highly suggestible (LDHS), and high dissociative highly suggestible (HDHS) participants completed the Stroop color-naming task in control and hypnosis conditions. The magnitude of conflict adaptation (faster response times on incongruent trials preceded by an incongruent trial than those preceded by a congruent trial) was used as a measure of cognitive control. LS and LDHS participants displayed marginally superior up-regulation of cognitive control following a hypnotic induction, whereas HDHS participants’ performance declined. These findings indicate that dissociative tendencies modulate the influence of a hypnotic induction on cognitive control in high hypnotic suggestibility and suggest that HS individuals are comprised of distinct subtypes with dissimilar cognitive profiles.     

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.     

Expert judgments of hypnosis from subjective state reports.

Suggestibility was assessed in 60 college students after a traditional hypnotic induction, an alert induction, progressive relaxation training, or instruction in goal-directed imagery. Responsiveness to suggestion did not differ between groups. Subjects also generated open-ended reports of their states of awareness and of their experience of 3 hypnotic suggestions. A sample of these reports from 24 moderately to highly suggestible subjects were evaluated by 18 experts in the field of hypnosis. Expert ratings of subjects' open-ended reports indicated that (a) traditional hypnotic inductions produce a state of consciousness that is indistinguishable from nonhypnotic relaxation training, (b) the subjective experience of hypnotic suggestions after imagination training is indistinguishable from that after hypnotic inductions, and (c) suggestibility is unrelated to state of consciousness as assessed by experts.     

Suggested visual hallucinations in and out of hypnosis

We administered suggestions to see a gray-scale pattern as colored and a colored pattern in shades of gray to 30 high suggestible and eight low suggestible students. The suggestions were administered twice, once following the induction of hypnosis and once without an induction. Besides rating the degree of color they saw in the stimuli differently, participants also rated their states of consciousness as normal, relaxed, hypnotized, or deeply hypnotized. Reports of being hypnotized were limited to highly suggestible participants and only after the hypnotic induction had been administered. Reports of altered color perception were also limited to high suggestibles, but were roughly comparable regardless of whether hypnosis had been induced. These data indicate that suggestible individuals do not slip into a hypnotic state when given imaginative suggestions without the induction of hypnosis, but nevertheless report experiencing difficult suggestions for profound perceptual alterations that are pheonomenologically similar to what they report in hypnosis.     

Hypnotic induction decreases anterior default mode activity

The ‘default mode’ network refers to cortical areas that are active in the absence of goal-directed activity. In previous studies, decreased activity in the ‘default mode’ has always been associated with increased activation in task-relevant areas. We show that the induction of hypnosis can reduce anterior default mode activity during rest without increasing activity in other cortical regions. We assessed brain activation patterns of high and low suggestible people while resting in the fMRI scanner and while engaged in visual tasks, in and out of hypnosis. High suggestible participants in hypnosis showed decreased brain activity in the anterior parts of the default mode circuit. In low suggestible people, hypnotic induction produced no detectable changes in these regions, but instead deactivated areas involved in alertness. The findings indicate that hypnotic induction creates a distinctive and unique pattern of brain activation in highly suggestible subjects.     

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.     

Imaginative Suggestibility and Hypnotizability

More than a half-century of research aimed at identifying the predictors of hypnotic responding has been described as investigations of 'hypnotizability'. Most of that research, however, has disregarded the well-established findings that (a) people respond to suggestion without being hypnotized almost as much as they do following a hypnotic induction, and (b) nonhypnotic and hypnotic suggestibility are highly correlated. More recent studies have provided the first empirical data on predictors of individual differences in response to the induction of hypnosis. These studies indicate that individual differences in hypnotic suggestibility can be accounted for completely by nonhypnotic suggestibility, expectancy, motivation, and reaction time. Because the amount of variance accounted for is as great as the reliability of the hypnotic-suggestibility scale, and because nonhypnotic suggestibility has been controlled, no additional variables are necessary to account for hypnotic suggestibility.     

Suggested visual hallucination without hypnosis enhances activity in visual areas of the brain

This functional Magnetic Resonance Imaging (fMRI) study investigated high and low suggestible people responding to two visual hallucination suggestions with and without a hypnotic induction. Participants in the study were asked to see color while looking at a grey image, and to see shades of grey while looking at a color image. High suggestible participants reported successful alterations in color perception in both tasks, both in and out of hypnosis, and showed a small benefit if hypnosis was induced. Low suggestible people could not perform the tasks successfully with or without the hypnotic induction. The fMRI results supported the self report data, and changes in brain activity were found in a number of visual areas. The results indicate that a hypnotic induction, although having the potential to enhance the ability of high suggestible people, is not necessary for the effective alteration of color perception by suggestion.     

Immediate and persisting effects of misleading questions and hypnosis on memory reports

Immediate and persisting effects of misleading questions and hypnosis on memory reports were assessed. After listening to a story, 52 highly suggestible students and 59 low and medium suggestible students were asked misleading or neutral questions in or out of hypnosis. All participants were then asked neutral questions without hypnosis. Both hypnosis and misleading questions significantly increased memory errors, and misleading questions produced significantly more errors than did hypnosis. The 2 effects were additive, so that misleading questions in hypnosis produced the greatest number of errors. There were no significant interactions with level of hypnotic suggestibility. Implications of these findings for the per se exclusion of posthypnotic testimony are discussed.     

Hypnotic control of attention in the Stroop task: a historical footnote

Raz, Shapiro, Fan, and Posner (2002) have recently provided a compelling demonstration of enhanced attentional control under post-hypnotic suggestion. Using the classic color-word interference paradigm, in which the task is to ignore a word and to name the color in which it is printed (e.g., RED in green, say "green"), they gave a post-hypnotic instruction to participants that they would be unable to read. This eliminated Stroop interference in high suggestibility participants but did not alter interference in low suggestibility participants. replicated this pattern and further demonstrated that it is not due to a visual strategy (such as blurring or looking at a different location). As a historical footnote, we describe a "case study" from 18 years ago in which we observed the same result using a hypnotic instruction to a single highly suggestible individual that he could not read. The elimination of Stroop interference has important implications for both the study of attention and the study 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.     

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.     

Hypnotic suggestibility predicts the magnitude of the imaginative word blindness suggestion effect in a non-hypnotic context

The present study investigated how the magnitude the word blindness suggestion effect on Stroop interference depended on hypnotic suggestibility when given as an imaginative suggestion (i.e. not post-hypnotic suggestion) and under conditions in which hypnosis was not mentioned. Hypnotic suggestibility is shown to be a significant predictor of the magnitude of the imaginative word blindness suggestion effect under these conditions. This is therefore the first study to show a linear relationship between the imaginative word blindness suggestion effect and hypnotic suggestibility across the whole hypnotizability spectrum. The results replicate previous findings showing that highs respond to the word blindness suggestion to a greater extent than lows but extend previous work by showing that the advantage for those higher on the hypnotizability spectrum occurs even in a non-hypnotic context. Negative attitudes about hypnosis may not explain the failure to observe similar effects of the word blindness suggestion in less hypnotizable individuals.     

Validity of a test of children's suggestibility for predicting responses to two interview situations differing in their degree of suggestiveness

In the present study the relative contributions of internal and external sources of variation in children's suggestibility in interrogative situations were examined. One hundred and eleven children (48 4- to 5-year-olds and 63 7- to 8-year-olds) were administered a suggestibility test (BTSS) and the most suggestible (N=36) and the least suggestible (N=36) children were randomly assigned to either an interview condition containing several suggestive techniques or to one containing only suggestive questions. The effects of internal sources of variation in suggestibility were compared with the effects of the interview styles on the children's answers. The former did influence the children, but the external sources of variation in suggestibility had a stronger impact. Influences of cognitive, developmental factors could be found, but not when abuse-related questions were asked and high pressured interview methods were used. These findings indicate that individual assessment of suggestibility can be of some assistance when interviewing children, but diminishing suggestive influences in interrogations must be given priority.     

Assessing the effects of misinformation on children's recall: how and when makes a difference

In two experiments children aged between 4 and 5 years and 7 and 8 years, respectively, participated in a real‐life event and were exposed to misleading questions immediately afterwards. The effects of variables relating to both the presentation of the misinformation and to the assessment of suggestibility were examined both immediately and following delays of 1 week (Experiment 1) or both 1 week and 1 month (Experiment 2). Older children were less suggestible than younger. Children were less suggestible when suggestibility was assessed in recall questions rather than misleading questions, less suggestible when information was central rather than peripheral and when the misinformation contradicted rather than supplemented the original event, and less suggestible over time in the absence of further suggestions. Providing cues had a small effect in enhancing resistance to the misinformation, but only when children were tested immediately. Embedding suggestions in a narrative context and repeating suggestions within a session led to greater suggestibility for both age groups, and repeating suggestions following a 1‐month delay had a particularly marked effect for the younger children. These findings are consistent with the view that suggestibility effects depend on the strength of the memory trace for the original information as well as that for the suggestion. How suggestibility is assessed is, however, also important and children's responses to misleading questions may not reflect their memory for the original event. Copyright © 2000 John Wiley & Sons, Ltd.     

Can expectation enhance response to suggestion? De-automatization illuminates a conundrum

Disparate theoretical viewpoints construe hypnotic suggestibility either as a stable trait, largely determined by underlying cognitive aptitude, or as a flexible skill amenable to attitudinal factors including beliefs and expectations. Circumscribed findings support both views. The present study attempted to consolidate these orthogonal perspectives through the lens of expectancy modification. We surreptitiously controlled light and sound stimuli to convince participants that they were responding strongly to hypnotic suggestions for visual and auditory hallucinations. Extending our previous findings, we indexed hypnotic suggestibility by de-automatizing an involuntary audiovisual phenomenon-the McGurk effect. Here we show that, regardless of expectancy modification, the experimental procedure led to heightened expectations concerning future hypnotic response. We found little effect of expectation, however, on actual response to suggestion. Our findings intimate that, at least in the present experimental context, expectation hardly correlates with--and is unlikely to be a primary determinant of--high hypnotic suggestibility.     

Does 'hypnosis' by any other name smell as sweet? The efficacy of 'hypnotic' inductions depends on the label 'hypnosis'

Hypnosis is associated with profound changes in conscious experience and is increasingly used as a cognitive tool to explore neuropsychological processes. Studies of this sort typically employ suggestions following a hypnotic induction to produce changes in perceptual experience and motor control. It is not clear, however, to what extent the induction procedure serves to facilitate suggested phenomena. This study investigated the effect on suggestibility of (a) a hypnotic induction and (b) labelling that procedure 'hypnosis.' Suggestibility of participants was tested before and after an adapted hypnotic procedure, which was either labelled as 'hypnosis' or as 'relaxation.' The hypnotic procedure produced a modest increase in suggestibility when it was called 'relaxation,' but a very significant increase if it was labelled 'hypnosis.' The results are important for both clinical and experimental applications and indicate that labelling an induction procedure 'hypnosis' is an important determinant of subsequent responses to suggestion.     

The effects of anxious mood induction on suggestibility to misleading post‐event information

Little research has been carried out into the effects of anxious mood at the time of either the encoding of misleading post‐event information or the time of its possible retrieval, on subsequent suggestibility. Participants comprised 160 first‐year undergraduates. Using a standard suggestibility paradigm, half of all participants were exposed to misleading information while half were non‐misinformed controls. In addition there were four state anxiety conditions, dependent on the timing of the anxious mood induction: at the time of encoding misleading information; at retrieval only; at both encoding and retrieval; or at neither encoding nor retrieval (controls). Results showed memory accuracy for non‐suggestible items was unaffected by the anxious mood induction. With respect to suggestibility, there was a strong effect of misleading information. In addition, within the misinformed group, all three groups who experienced the anxious mood induction were significantly less suggestible than controls. These findings are discussed both in terms of theories of anxiety and cognition and the applied implications for the increasing use by the police of video‐recorded witness interviews. Copyright © 2004 John Wiley & Sons, Ltd.