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.     

Hypnosis and interrogative suggestibility

An attempt was made to induce memory errors through the use of misleading questioning in hypnosis. Subjects heard a short newslike story and gave initial free recall for the story details, then 4 days later were given three free recall trials: prior to hypnosis, following hypnotic induction and suggestion for enhanced memory, and after hypnosis was terminated. During hypnosis subjects were also twice interrogated with either misleading or objective questions for the story details. Accurate memory increased over the three free recall trials for all subjects regardless of hypnotizability. In recognition testing, subjects given misleading questions during the interrogation gave fewer correct responses, had more errors-in-fact as well as forgetting, and showed an increase in yielding to interrogative suggestibility over trials than subjects given objective questions. All subjects subsequently confabulated more information on the final awake free recall trial as a result of errors introduced during hypnotic interrogation process. These results help to clarify the inherent dangers in relying on hypnosis to enhance memory.     

Involvement in everyday imaginative activities, attitudes toward hypnosis, and hypnotic suggestibility.

One hundred male and 83 female subjects were assessed on absorption (i.e., involvement in everyday imaginative activities), attitudes toward hypnosis, and hypnotic suggestibility. Significant positive correlations were obtained for both sexes between absorption and attitudes and between each of these variables and hypnotic suggestibility. Multiple regression analyses indicated that most of the predicted variance in hypnotic suggestibility scores was accounted for in both sexes by the absorption variable.     

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.     

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.     

Is hypnotic suggestibility a stable trait?

The present study examined the trait-like nature of hypnotic suggestibility by examining the stability of hypnotic responsiveness in a test-retest design in which the procedures were administered either live or by audiotape. Contrary to the idea that hypnotizability is a largely immutable, stable trait, scores on the scale of hypnotic responsiveness decreased significantly at the second session. Measures of subjective experiences and expectancies accounted for a sizable portion of the variance in hypnotic responding, both at initial test and at retest. Participants became disengaged with the hypnotic procedures at retest. Participants who received the hypnotic induction by audiotape did not differ from participants who received it live. The results are consistent with sociocognitive and altered state theories of hypnosis, and underline the important role of subjective experiences in hypnotic responding.     

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.     

Methodological and practical issues regarding phenomenological subtypes of highly suggestible individuals: A response to Kumar

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.     

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.     

Seeing is believing: the reality of hypnotic hallucinations

Two experiments investigated the reality attributed to hypnotic suggestion through subtle projection of a visual image during simultaneous suggestion for a visual hallucination that resembled the projected image. In Experiment 1, high and low hypnotizable participants were administered either a hypnotic induction or wake instructions, given a suggestion to hallucinate a shape, and then the projected image was subsequently introduced. Although highs in both conditions rated the projected image more vividly than lows, highs in the hypnosis (but not wake) condition made comparable reality ratings when the projected image was absent and present. In Experiment 2, high hypnotizable participants were administered a suggestion to see a shape on a wall. For half the participants the suggested image was projected on the wall and then removed, and for half the projection was initially absent and then introduced. Participants who had the projection absent and then present reported comparable reality and vividness ratings when the projection was absent and present. These findings indicate that elevated hypnotizability and hypnosis are associated with attributions of external reality to suggested experiences.     

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.     

Hypnotic pseudomemories,prehypnotic warnings,and the malleability of suggested memories

This study used Orne's nocturnal events paradigm to test the effects of warning highly hypnotizable participants about the possibility of hypnotic false memories. We found that warnings reduced suggestibility but not false memories during hypnosis. Fewer warned participants (12/32, 38 per cent) than unwarned participants (12/16, 75 per cent) accepted the suggestion to hear a noise that awakened them when they were age-regressed to a night of the previous week. However, an analysis of only those persons who accepted the suggestion during hypnosis showed that the warning had no effect on their posthypnotic pseudomemories: among this group, 75 per cent of warned versus 58 per cent of unwarned persons stated immediately after hypnosis that the noise occurred in reality (i.e., reported a pseudomemory). During a final confidential assessment, 58 per cent of the warned participants who had accepted the noise suggestion reported a pseudomemory, versus 50 per cent of the unwarned participants. Comparing pseudomemory rates across all participants, regardless of whether they passed or failed the noise suggestion, 28 per cent of warned participants versus 44 per cent of unwarned participants reported pseudomemories, a nonsignificant difference. Finally, warned and unwarned participants were equally confident in their false memories. © 1998 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.     

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.     

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.     

Creating false memories of infancy with hypnotic and non‐hypnotic procedures

This study was designed to test the conditions under while false memory reports are likely to be elicited from hypnotic and non‐hypnotic participants. Low, medium and high hypnotizables were administered either a hypnotic or non‐hypnotic suggestion for regression to the day after birth. False memories of infancy were generated in 68 of 78 age‐regressed participants, nearly half of whom reported strong beliefs in the reality of their recovered ‘memories’. Non‐hypnotic participants were slightly but significantly more likely to report infancy experiences than were hypnotic participants. However, hypnotizability did not have a significant effect on the classification of these experiences as memories or as fantasies. Implications for the experimental and clinical contexts are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

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.     

Alteration of hypnotic experience following transcranial electrical stimulation of the left prefrontal cortex

BackgroundRecent studies of neurostimulation reported alteration of hypnotizability and hypnotic phenomena after inhibition of the dorsolateral prefrontal cortex (DLPFC), but the different assessments of hypnosis and the stimulation parameters still left open many questions about the role of this brain region in hypnotizability. We aimed to administer inhibitory transcranial direct current stimulation (tDCS) over the left DLPFC to observe effects of stimulation on the hypnotic experience and the feeling of agency.Methodsa procedure of hypnotic induction with suggestions was repeated twice: before and after the unilateral cathodal tDCS over the left DLPFC. The experience was assessed through a phenomenological assessment of hypnosis and sense of agency in thirty-three participants randomly assigned to the sham or the active group.Resultsactive (inhibitory) tDCS enhanced the hypnotizability by 15.4% and altered a few dimensions of consciousness such as self-awareness and absorption. No changes emerged on the feeling of agency and pass rates for suggestions.ConclusionstDCS reflects a promising tool to alter the hypnotic phenomena and the responsiveness to hypnotic procedures. Neurocognitive implications are discussed for the construct of hypnotizability as well as for the role of the left DLPFC in the dimensions of consciousness such as self-awareness.     

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.     

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.