A review and methodological critique. Updates Putnam, 1984. Currently, psychophysiologic differences reported in the literature include changes in cerebral electrical activity, cerebral blood flow, galvanic skin response, skin temperature, event- related potentials, neuroendocrine profiles, thyroid function, response to medication, perception, visual functioning, visual evoked potentials, and in voice, posture, and motor behavior. Reviews the new research on the psychophysiological investigation of MPD from published, unpublished, and ongoing studies, and attempts to place current findings into a conceptual framework. Authors note results from unpublished and ongoing studies and include a critical analysis of current research methodology as well as suggestions for future research.

Arendt-Nielsen, Lars; Zachariae, Robert; Bjerring, Peter (1990). Quantitative evaluation of hypnotically suggested hyperaesthesia and analgesia by painful laser stimulation. Pain, 42, 243-251.

Sensory and pain thresholds to laser stimulation were determined, and the laser-pain evoked brain potentials were measured for 8 highly hypnotizable (Harvard Scores 10-11) student volunteers in 3 conditions: (1) waking, (2) suggestion of hyperaesthesia during hypnosis, (3) suggestion of analgesia during hypnosis.
The investigators used a laser beam 3 mm in diameter, with a 200 msec stimulus duration; the same area (but different points within the area) was used for consecutive stimulations. Ss were otherwise maintained in low stimulus conditions so they would not have visual or auditory cues about laser beam onset; they wore goggles, had eyes shut, and had earphones on. Sensory threshold was defined as warmth; pain threshold was defined as a distinct sharp pin prick.
The laser intensity used for stimulation corresponded to strong pain. Interstimulus intervals averaged 15 sec (but were randomly varied between 10-20 sec). Sensory and pain thresholds as well as two evoked potential measurements were taken during waking , hypnotized hyperaesthesia, and hypnotized analgesia conditions in a single 1 1/2 hour session.
The evoked potential component of interest was the negative complex N1 with latency of 300 msec; amplitude (P1=N1-P2) and latency of this complex (N1) were measured. EEG epochs contaminated by eye movement were omitted from analysis.
The standardized induction and deepening of hypnosis required 15-20 minutes; then the suggestion was given that Ss could alter their perception of stimuli such as pain. Hyperaesthesia suggestions were to imagine the right hand was in very hot water, then taken out but still very red, hot, sensitive so that even the vaguest stimulus would be detectable and unpleasant. They were told that they would receive a series of painful but tolerable stimuli, and to raise the left index finger if they could just perceive a laser pulse (sensory threshold), and again if they felt pricking pain (pain threshold).
Suggestions for analgesia were to imagine that their right hand was placed on their chest, and that their ‘former right hand’ was no longer their own but was made of some heavy and completely insensitive material like wood or stone. Sensory and pain threshold measures were then taken. During the evoked potential measurement period they received continuous suggestions of analgesia. They also were told to relax and imagine they were in a pleasant place, ignoring everything except the pleasant, relaxed feelings and imagining pleasant sights, sounds, feelings and the imagined place. They were told that though they would receive stimuli, they probably would be able to ignore the stimuli completely.
Results were as follows.
1. In the hypnotic hyperaesthesia condition, sensory and pain thresholds decreased significantly by 47% and 48%, respectively. Three Ss reacted to laser intensities far below what normally can be perceived in the waking state. [The authors ran a separate small control experiment to make sure that the Subjects were not using any other cues, but mention the possibility of light-sensitive skin reacting to the blue laser light, creating evoked potentials.]
2. In the hypnotic analgesia condition, sensory and pain thresholds increased by 316% and 190%, respectively. 7 of 8 Ss did not even respond to pain threshold when the laser intensity was increased to the noxious level of 3W, which is the level at which tissue damage can occur.
3. Pain-related evoked potentials. Amplitude of the first pain-related potential was increased significantly by 14% in the hyperaesthesia condition and reduced significantly by 31% in the analgesia condition. Changes in the evoked potentials were considered minor however compared to those observed for thresholds, which are subjective response measures. Even in Subjects who reported complete analgesia, the experimenters observed the laser pain evoked responses. There were no differences in latencies of the first pain-related potentials for the three conditions (indicating that peripheral and central afferent conduction velocities were the same).
Discussion. “There has been some dispute concerning the experimental design and the reliability of the data obtained in studies dealing with hypnotic suggested analgesia [Spanos & Chaves, 1970]. In our design 2 ‘opposite’ conditions were induced, and the 2 inductions gave ‘opposite’ results.
“The experience of pain can be significantly altered by suggestions of analgesia, which is in accordance with a number of other studies (for review see [Barber & Adrian, 1982; Hilgard & Hilgard, 1975]). The finding that suggestions of hyperaesthesia can decrease the sensory and pain thresholds and increase the amplitude of the pain evoked potential is a new observation. Since synchronized auditory and visual stimuli from the laser were blocked, and the stimulus was given at random intervals, the changes might be induced by the hypnotic suggestions” (p. 247).
The authors discuss their results in terms of (1) four pain modulation systems (neural/opiate, hormonal/opiate, neural/non-opiate, and hormonal/non-opiate) and (2) focusing and defocusing attention. Because in their pilot study it was necessary to give suggestions continually in order to affect the laser evoked potentials, they conclude that endogenous substances or hormonal/non-opiates would play a minor role, if any, in hypnotic analgesia. (Price and Barber [25] had also found it important to give suggestions continuously.)
On the other hand, “event-related potentials [7, 26] and pain-related potentials have, previously, been shown to be sensitive to focused and de-focused attention. Recently, Miltner et al. [23] showed the influence of attention on the late pain-related component of potentials, evoked by painful intracutaneous electrical stimulation. The degree to which the subject paid attention to the painful stimulus had a powerful effect on the pain-related complex. When subjects ignored the pain, it was still possible to record the pain-related complex although all the subjects consistently reported less or no pain. In wakeful subjects where cutaneous pain was abolished by lignocaine infiltration, the pain-related evoked potentials were abolished [4]. In our study, we could also record evoked potentials although the subject subjectively did not feel pain. The reason might be that the S acted as if there was full analgesia to the stimuli, in order to satisfy the hypnotist. During suggested hyperaesthesia the thresholds declined below what normally could be perceived in the wakeful state. The volunteers could, therefore, not act hypersensitive, so something did happen.
“The discrepancy in subjective and objective responses might, however, be useful when investigating levels of the neuroaxis at which hypnosis might work” (pp. 248-249).
The authors note that this laser induced pain and the tooth pulp stimulation pain of Mayer & Barber both use the A-delta fibers. Barber & Mayer found it impossible to elicit pain within the output range of the stimulator (up to 150 microA) and reached maximal intensity for all volunteers during suggested analgesia. Using cutaneous laser stimulation the authors found that the skin damage level (3W) could be reached in 7 of 8 volunteers without any reaction of pain.
During the hyperaesthesia condition the sensory threshold was sometimes lower than can be detected in the waking state. Although some researchers have suggested that red light from a helium-neon laser might activate cutaneous photosensitive receptors and thereby elicit brain potentials, the authors were unable to elicit potentials in waking Subjects using their blue and green argon laser light with below sensory threshold intensity.
The authors also note that previous attempts to use physiological correlates of pain such as heart rate, blood pressure, respiration, and galvanic skin response have yielded confusing results. The physiological indicators are present even when Subjects report analgesia, leading some investigators to conclude that the subjective reports are due to illusion [Sutcliffe, 1961], compliance [Wagstaff, 1986], or a placebo induced by the hypnosis context [Wagstaff, 1986]. “These confusing results lead to the conclusion that both the traditional methods used for induction of pain and the monitored physiological responses have been unsatisfactory. The present study has sought to eliminate some of the methodological difficulties by (1) using brief well-defined argon laser stimuli which in awake volunteers induce very stable perceptions between trials [Arendt-Nielsen & Bjerring, 1988], and (2) recording psychophysical thresholds and objective parameters quantitatively related to the intensity of the pain perceived (1, 3)” (p. 249).

Spiegel, David; Bierre, Pierre; Rootenberg, John (1989). Hypnotic alteration of somatosensory perception. American Journal of Psychiatry, 146, 749-754.

The effects of hypnotic alterations of perception on amplitude of somatosensory event-related potentials were studied in 10 highly hypnotizable (HH) Subjects and 10 Subjects with low hypnotizability. The HH Subjects showed significant decreases in amplitude of the P100 and P300 waveform components during a hypnotic hallucination that blocked perception of the stimulus. When hypnosis was used to intensify attention to the stimulus, there was an increase in P100 amplitude. Findings are consistent with observations that HH individuals can reduce or eliminate pain by using purely cognitive methods such as hypnosis. Together with data from the visual system, these results suggest a neurophysiological basis for hypnotic sensory alteration.

Four conditions were presented in random order to each Subject. Normal Attention – subjects were instructed to button-press each time they felt the target stimulus. Passive Attention – subjects were instructed to attend to the stimuli but not button-press. Hypnotic Attention – subjects received a hypnotic induction (eye closure and arm levitation, which provided behavioral confirmation; then instructed to attend carefully to the stimuli, which they were told to experience as ‘pleasant and interesting,’ and button-press in response to targets. Hypnotic Obstructive Hallucination – hypnotic induction exercise was followed by the hypnotic suggestion of a local anesthetic, such as novocaine, spreading from fingers to hand to forearm on the stimulated limb; then instructed to make the limb cold, tingling, and numb; then told to button-press if they felt any of the target stimuli.
Experimenter was blind to hypnotizability scores.
Results were that the Highs showed significant decreases in P100 (45%) and P300 (38%) amplitudes during a hypnotic hallucination which blocked perception of the stimulus, but an increase (35%) in P100 amplitude when hypnosis was used to intensify attention to the stimulus. The authors view this as cognitive flexibility akin to the clinical situation in which high hypnotizables reduce or completely eliminate pain. They consider this evidence (along with earlier findings on similar blocking of perception in the visual system) of a neurophysiological basis for hypnotic sensory alteration.

Aravindakshan, K. K.; Jenner, F. A.; Souster, L. P. (1988). A study of the effects of hypnotic regression on the auditory evoked response. International Journal of Clinical and Experimental Hypnosis, 36, 89-95.

Hypnotic regression in 6 hypnotizable Ss experienced in regression was studied by means of the auditory evoked response (AER). AER latency and amplitude is affected by arousal, attention, stimulus strength, and age. Ss aged between 27 and 61 years were regressed to the age of 7-9 years, and AERs were compared among three states of consciousness: normal awareness, hypnotic relaxation, and hypnotic regression. There was no change in AER morphology in the direction of that seen in children. Thus, age regression is not seen as a reversion to an earlier stage of neurological development but perhaps as role playing which is spontaneous and uninhibited, with the benefit of innocent belief in its accuracy.

Raikov (1982) regressed 2 experienced Ss, comparing his results with those of actors acting as children and low hypnotizable subjects; he claimed to be able to reproduce neonatal reflexes in the highly hypnotizable Ss but not in the actors and low hypnotizable subjects.
AER’s were used “because latency of the major waves and amplitude of the response is affected by level of arousal and attention…, strength of the stimulus, and, more importantly for this study, by age…. Surwillo (1981) noted that peak latencies of AERs were 16-21 msec longer in children aged 9-13 than in adults…” (p. 90)

DISCUSSION reviews the literature.
Changes in the intensity of light stimulation can cause significant shifts in the amplitude and latency of the visual evoked response, but neither the amplitude nor the latency have been changed by suggested alterations in stimulus intensity during hypnosis (Andreassi, Balinsky, Gallichio, de Simone, & Mellers, 1976; Beck & Barolin, 1965; Beck, Dustman, & Beier, 1966; Zakrzewski & Szelenberger, 1981). Similarly, significant changes were seldom found in the AER with suggested variations of sound intensity during hypnosis (Amadeo & Yanovski, 1975) and in somatosensory responses to electrical stimuli applied to the fingers with suggested anesthesia during hypnosis (Halliday & Mason, 1964). Deehan and Robertson (1980) were able to abolish the AER completely during hypnosis, but their stimuli were very different from that used in the present study.
“In all such studies, hypnosis and suggestions were aimed at changing the intensity of the stimulus to S’s awareness, while the actual intensity of the stimulus was unaltered. In the present study, the authors attempted to find whether the morphology of the AER in children could be reproduced by age regression, without altering the nature or intensity of the stimulus in its delivery…. Like previous investigators, the present authors noticed that the tracings were cleaner and easier to produce during hypnosis (see Figure 1), although the changes in neurological development observed by Raikov (1982) were not evident” (pp. 93-94).

Spiegel, David; Barabasz, Arreed F. (1988). Effects of hypnotic instructions on P300 event-related-potential amplitudes: Research and clinical applications. American Journal of Clinical Hypnosis, 31, 22-27.

Apparently conflicting findings in two recent studies of the effects of hypnotic hallucination on the P300 component of cortical event-related potentials are examined. In one study, Barabasz and Lonsdale (1983) found an increase in P300 amplitude in response to hypnotic anosmia instructions. However, Spiegel, Cutcomb, Ren, and Pribram (1985) obtained a decrease in P300 amplitude after instructing high hypnotizables that an imaginary cardboard box blocked their view of the stimulus generator. These differences are reconciled on the basis of differences in the hypnotic instructions given. The former study employed language which emphasized negation (“You will not smell anything at all”), while the latter had subjects focus on a competing obstructive hallucination. The anosmia subjects were surprised when they smelled anything at all, leading to an enhanced P300 response, while the subjects in the visual study were so absorbed in the hallucinated obstruction that perception of the stimulus was reduced. Clinical implications of these two studies are examined.

Meszaros, Istvan; Banyai, Eva I.; Greguss, Anna C. (1985). Evoked potential correlates of verbal versus imagery coding in hypnosis. In Waxman, David; Misra, Prem C.; Gibson, Michael; Basker, M. Anthony (Ed.), Modern trends in hypnosis (pp. 161-168). New York and London: Plenum Press.

In our previous works it has been demonstrated that late components of midline evoked potentials recorded in the associative cortical areas do reflect significant modifications of selective attention caused by hypnosis. More and more data can be found in the literature indicating that subdominant hemispheric functions–significant in imagery coding–are more expressed in hypnosis as compared to the waking state. The purpose of the present experiment was to study how the motor reactions and the bilaterally recorded evoked potentials reflect the hypnotic modifications in processing visually exposed vs. imagery commands. A warning tone signal was followed by a tachistoscopically exposed verbal or imagery command to push a button either by the right or the left hand, according to the content of the command. Correct and incorrect responses and their reaction time were recorded together with the registration of EEG, EMG, ECG, EOG and evoked potentials in frontal, central, and occipital right and left monopolar leads. The alterations of the motor responses and of the negative evoked potential peak appearing with 120 ms latency and of the positive peaks with 200 and 300 ms latencies showed characteristic differences as functions of verbals vs. imagery task (i.e. dominant vs. subdominant hemispheric processing) as a result of hypnosis.

Spiegel, David; Cutcomb, Steven; Ren, Chuan; Pribram, Karl (1985). Hypnotic hallucination alters evoked potentials. Journal of Abnormal Psychology, 94 (3), 249-255

Brain electrical potentials evoked by visual stimulation were analyzed to study the neurophysiological mechanism associated with hypnotic hallucination. The visual evoked responses of 6 high- and 6 low-hypnotizable subjects were compared in three hypnotic conditions: stimulus enhancement, stimulus diminution, and stimulus elimination (obstructive hallucination). High-hypnotizable individuals demonstrated significant suppression of the later components of the evoked response (N1 and P3) while experiencing obstructive hallucinations, indicating a change in information processing. This effect was significantly greater in the right, as compared to the left, occipital region.

In the stimulus enhancement condition, Ss were told that one of two colored stimuli would appear unusually bright and interesting. In the stimulus diminution condition, Ss were told that the alternate color stimulus would appear drab, dull, uninteresting. In the obstructive hallucination condition, Ss were told to visualize a box that blocked their view of the TV monitor, making it impossible to see anything on the TV screen. The stimuli were 8 cm x 8 cm squares (colored gratings) presented 1 meter in front of S: 50% were blue vertical gratings, 50% were pink horizontal gratings.
Ss were told to press a button in response to any stimulus they happened to see; hence all stimuli were potential targets. To control for the effect of motor potentials when they pressed the button, a button-pressing/passive-attention control group was added. Only results significant beyond this control group were attributed to a hypnotic hallucination effect. A second control group of medium level hypnotizable Ss were required to (a) button press after each stimulus presentation and (b) attend passively to the TV monitor screen without button pressing. “Thus, we had three control conditions: (a) for attentional demands, comparing the performance of high hypnotizables in the obstructive hallucination versus the hypnotic stimulus enhancement condition, (b) for hypnotizability, in comparing the high hypnotizables in the obstructive hallucination condition versus the low hypnotizables in the same condition, and (c) for button-pressing behavior, comparing the performance of the high hypnotizables to that of control subjects in press versus no-press conditions” (p. 250).
In their discussion, the authors state, “Our results are consistent with the hypothesis that an hypnotic instruction of obstructive hallucination among high- hypnotizable subjects is accompanied by a decrease in the amplitude of the P3 component of the evoked response throughout the brain, and of the N2 and P3 components in the occipital region. This dampening of amplitude is particularly notable among high hypnotizables in the right, as compared with the left, occipital area, suggesting greater inhibition of scalp-recorded response to a visual stimulus in the right hemisphere.
“These data show that while experiencing an obstructive hallucination blocking the stimulus, high-hypnotizable subjects demonstrate a change in the information-processing components of the evoked response (Baribeau-Braun, Picton, & Gosselin, 1983), rather than primarily in channel selection, which is reflected more by P1 and N1 (Ford, Roth, Dirk, & Kopell, 1978; Hillyard & Picton, 1979). Although there were differences at P1 and N1 between high and low hypnotizables, they were not significantly greater than those observed in the press/no-press control group. These observations make it possible to address several alternative explanations for the findings, such as the possibility of differences in nonspecific arousal leading to a differential preparation (Naatanen, 1969), which should be reflected primarily in changes in the early components, as would any differences in pupil size. Drowsiness or inattention in this condition should be associated with an increase, rather than a decrease, in response amplitudes (Schacter, 1976). The possibility that high hypnotizables might have defocused their view of the monitor (Schulman-Galambos, & Galambos, 1978) is made less likely by the fact that defocusing is accompanied by increases in P1 latency (Sokol & Moskowitz, 1981), whereas there were no P1 latency differences in the obstructive hallucination condition” (p. 254).

Hogan, Marjorie; MacDonald, John; Olness, Karen (1984). Voluntary control of auditory evoked responses by children with and without hypnosis. American Journal of Clinical Hypnosis, 27 (2), 91-94.

Reports ability of children to voluntarily change brainstem auditory evoked responses (BAER). Fifteen children were studied. Both control and hypnosis groups showed changes in interwave latencies after verbal suggestions when compared to a normal control group. These findings suggest that children may be able to modify peripheral auditory input into the brainstem through simple suggestion alone. Children in the formal hypnosis group did have more specific control for the task suggested. However, it is possible that children in the control group moved into an altered state of consciousness after listening to a taped story, reading a book, or spontaneously. They may have attained the observed changes in BAER while in a hypnosis-like state. This study encourages additional research in self-regulatory skills of autonomic processes in children.

Barabasz, Arreed F.; Lonsdale, Christopher (1983). Effects of hypnosis on P300 olfactory-evoked potential amplitudes. Journal of Abnormal Psychology, 92 (4), 520-523.

From a sample of 93 undergraduates, 4 high- and 5 low-hypnotic susceptibility (the Stanford Hypnotic Susceptibility Scale: Form C) Ss were exposed to a waking condition and a hypnotic induction condition that included a suggestion for anosmia. ANOVAs of the P300 showed significant amplitude increases for weak and strong odors for high-hypnotizable Ss in hypnosis, but not for high-hypnotizable Ss in the waking state. No such amplitude increases were found for the low-hypnotizable ss

Nash, John (1983). Negative visual hallucination and concomitant changes in cortical event-related potentials (Dissertation, University of California, Santa Barbara). Dissertation Abstracts International, 45 (2), 716-B. (Order No. DA 8411224)

The purpose of this investigation was to examine the effects of negative visual hallucination (NVH) on cortical event-related potentials (ERPs), and to compare these effects with those of selectively attending to and ignoring stimuli. Five highly hypnotically susceptible subjects, four female and one male, were trained to block from subjective experience, i.e., negatively hallucinate, a ring of strobe-illuminated circles surrounding a central, independently strobe-illuminated circle. This stimulus array was modeled after part of the Titchener-Ebbinghaus circle illusion, since previous research had shown that subjects could attenuate the effects of the optical illusion via NVH of the outer, illusion-producing circles. “Analysis of the ERP data revealed amplitude and latency changes in various ERP components across the three experimental conditions (Attend, Ignore, NVH) for the four female subjects, a negative result which is explained in motivational terms. “The most noteworthy finding was the selection of the P3 amplitude variable at C2 by stepwise discriminant analysis for the four females, and the fact that this amplitude systematically decreased across conditions from largest in Attend to smallest in NVH. A variety of individual patterns were observed in terms of other ERP components which allowed discrimination (successful classification) among the three conditions. The results suggest that both Ignoring and NVH of a stimulus result in a decrease in the subjective certainty of perception of the stimulus. Individual differences in patterns of ERP changes are interpreted in terms of differing strategies for execution of the experimental instructions. The results support the view that NVH instructions produce distinctive ERP effects and that NVH generally can be viewed as an extreme level of ignoring” (p. 716).

Cutcomb, Steven Donald (1982, May). Studies in the brain correlates of human cognitive function (Dissertation, Stanford University). Dissertation Abstracts International, 42 (11), 4609-4610-B.

Three studies in the electrophysical correlates of human cognitive function are described. In study one, colored gratings were presented tachistoscopically to humans in two selective attention paradigms based upon the design of Hansen and Hillyard (1980), and Hillyard, Hink, Schwent, and Picton (1973). Visual event-related potential (ERP) data from Fz, Cz, Pz, T5, T6, O1, and O2, and behavioral responses were collected, and averaged ERPs were subjected to feature extraction (P1, N1, P2, N2, and P3 amplitudes and latencies) as well as a principle components factor analysis. Both analyses revealed as a significantly larger N2 component in the visual ERP, peaking at 310 msec and maximally frontally, during attending to task-relevant (attended-channel) stimuli. The P3 component was significantly larger in response to all attended-channel stimuli. In study two, the task was repeated using a group of six high and six low susceptible subjects during hypnosis. ERPs from Fz, Cz, Pz, O1, and O2, and behavioral responses were recorded during the task, and during a hypnotic suggestion of a negative hallucination (obstructed view of the stimulus monitor) while the stimuli were presented. The averaged ERP data was subjected to feature extraction followed by analyses of variance. No inter-group differences were found in the ERPs during the selective attention tasks. “During the obstructed view suggestion, the lows showed a normal visual ERP, while the highs had a visual ERP with a significantly diminished P1, P2, N2, and P3 component amplitude at O1 and O2. These results are evidence for an altered brain response during the obstructed view suggestion in high susceptible hypnotized subjects. “In study three, EEG were recorded from twelve high and twelve low susceptible hypnotic subjects (frontal, central, occipital) during baseline and hypnotized conditions. Data were transformed to normalized theta and alpha-band power spectral averages for each group. No significant inter-group alpha differences were found. Highs had significantly more relative theta energy frontally. During hypnotic tasks, the highs showed higher relative theta power at all leads. These results are consistent with the trait conception of hypnotic susceptibility” (pp. 4609-4610).

Blum, Gerald S.; Nash, John; Jansen, Robert D.; Barbour, John S. (1981, June). Posthypnotic attenuation of a visual illusion as reflected in perceptual reports and cortical event-related potentials. Academic Psychology Bulletin, 3, 251-271.

Highly selected and trained hypnotic subjects, capable of ablating portions of visual stimuli from conscious awareness, showed varying degrees of ability to attenuate the Titchener-Ebbinghaus circles illusion post-hypnotically under a negative visual hallucination instruction. The presence or absence of such inhibitory skill, inferred from perceptual reports, was differentially reflected in changes in cortical event-related potentials not typically associated with shifts in selective attention. These findings point to the cognitive operation of a distinctive mechanism of selective inattention.

Blum et al. postulate an inhibitory mechanism of the central nervous system with stages of amplification and attenuation. They suggest that individual differences in inhibitory skill may be improved with practice even for very skilled Subjects. They studied this type of inhibition using a visual illusion (the Titchener-Ebbinghaus circles) because the neural locus of such illusions is thought to be more central in the nervous system rather than at the level of the retina.
Experiment 1. Three Ss trained in using hypnosis viewed stimuli in waking and posthypnotic negative visual hallucination (NVH) conditions. All three had previously passed a negative hallucination item (not seeing a playing card of three such cards placed on a table). Training included practice sessions applying NVH to the experimental stimuli. S1 reported immediate success; S2 experienced some initial difficulty (“I have a feeling something’s there”) but then reported success; S3 required a couple of long practice sessions.
The classic Titchener-Ebbinghaus illusion stimuli were used. Stimuli were ten slides with drawings of a standard 17-mm-diameter black circle on the left and a comparison black circle on the right. The black circle on the right was either 14, 15, 16, 17, or 18 mm in diameter, skewed intentionally around 17, to compensate for the proportion of smaller and larger judgments applied to the comparison figure in relation to the standard. One black comparison figure was surrounded by seven 15-mm diameter white circles; the other by seven 10 mm diameter white circles. The key drawings were both black circles of 17 mm. The second set of five drawings, used as a control, contained the same black circles but lacked outer rings of white circles.
The Subject was to state whether the black circle on the right appeared larger, smaller, or the same as the standard black circle on the left. Slides were shown for 4 seconds each, with 6 seconds in between slides.
Alternating blocks of trials were given under baseline (B) condition and a posthypnotically programmed negative hallucination condition (NVH). In the NVH condition, “the rings of white circles surrounding the standard and comparison black inner circles were ‘ablated’ from consciousness. The observers were amnesic in the waking state for their prior hypnotic instructions and were cued in advance of a block of trials simply by the phrases ‘This will be a mixed series’ (referring to B, in which the stimuli appeared as they really were, some with outer rings of white circles present and others not), or ‘This will be a black only series’ (referring to NVH, in which all stimuli appeared to the observer as black circles only, whether the outer rings were physically present or not)” (pp. 254- 255). Sessions were spread out over 8-12 months for each observer, interspersed with a variety of other experiments.
In one session the Experimenters used a selective attention instruction, with Ss given posthypnotic suggestions to regulate their cognitive arousal to a peak of mental alertness and concentration (+AA) and focus on the inner black circles but not to negatively hallucinate the outer white circles.
Although all three Ss showed the illusion effect, they varied in ability to attenuate the illusion when negative visual hallucination suggestions were given. “S1 showed a very greatly reduced frequency of reports in the illusory direction under the NVH condition, a less marked reduction under +AA concentration, and no reduction at all under a waking instruction to ignore the outer circles; S2 revealed a moderate but significant reduction under NVH but not under +AA; S3 gave no evidence of attenuation in either condition” (p. 258). The response times for the two more successful Ss (1 and 2) with the 17 mm stimuli under NVH conditions were not different when the outer circles were either present or absent.
Experiment 2. The next year S1 and S2 returned but S3 was no longer available as a Subject; S4 and S5 were added and trained in hypnosis skills. EEG evoked response potentials (ERPs) were recorded while Ss made size judgments as in Experiment 1. Averaged ERPs for each block of 100 stimulus presentations were obtained for the first 500 milliseconds following stimulus onset. Judges blind to the experimental conditions evaluated the ERP records.
All Subjects experienced the Titchener-Ebbinghaus illusion, but again there were individual differences in ability to attenuate the illusion: S1 was the most successful; S2 gave significantly fewer responses in the larger category under NVH than B conditions; and both S1 and S2 improved attenuation performance over the previous year. S4 fell between S1 and S2 in ability; S5 was unable to attenuate the illusion in the NVH condition.
Results. “All three observers whose perceptual reports indicated some attenuation of the visual illusion during the NVH condition also showed a consistent reduction of the P2-N2 amplitude during NVH” (p. 262) at the Occipital sites. Median amplitude reduction was 36%, 40%, and 36% for S1, S2, and S4; only 7% for S5. There were no similar reductions for the other electrode sites, though “enhancement of P2-N2 amplitudes occurred in the lateral prefrontal and frontal areas in the two most successful individuals, S1 and S4” (p. 263). There was also a lag in N2 peak latencies for the three best subjects. The Experimenters noted that the N2 peak occurred 50 msec later in the frontal and prefrontal areas than in the occipital area.
In their Discussion, the authors express the view that it is not likely that faking could have occurred, for several reasons: 1. The Subjects were trained to report honestly, and they often had reported failures to experience hypnotic phenomena suggested during training sessions. 2. The task elicited rapid responses, usually in less than 2 seconds, to 10 different slides in randomized blocks of 100 trials, which would make self monitoring of responses extremely difficult. 3. Subjects exhibited a consistency of responses over experimental sessions that were widely separated in time, making conscious or unconscious deception unlikely. 4. The finding of no difference in latency between 17 mm stimuli with and without outer rings of white circles supports an interpretation of reliable reporting. 5. Differences in ERP data between the B and NVH conditions were obtained only for those Ss who successfully attenuated the illusion.
The authors also state, “In terms of our conceptual model of the mind, inhibitory skill is attributable to the capacity for invoking inhibitory action earlier in the sequence as signals are processed through stages of amplification and attenuation en route to consciousness (Blum & Barbour, 1979). In the NVH condition of the present task, first- stage attenuation … [Subject 1] … occurs in time to negate the illusion as well as preventing conscious awareness of the outer white circles, second-stage attenuation takes place too late to disrupt the illusion but still in time to keep the outer circles from consciousness” (p. 265). Note that the unsuccessful Subject 5 had the highest score on the screening hypnotizability tests. The variation among very high hypnotizables casts doubt on the practice of grouping Ss who score between 9 and 12 on the SHSS. “It is perhaps not surprising that many previous hypnotic studies involving alterations in such subtle phenomena as visual illusions have yielded negative results.” p. 266.
N.B. None of the Ss was able to eliminate the illusion under a strong waking instruction to ignore the outer circles while judging the inner black ones. “These different results for AA and NVH instructions pinpoint the contrast between selective attention (+AA) and selective inattention (NVH)” (p. 266).
The ERP changes seen in occipital and frontal areas were in opposite directions. Thus “the data suggest an effect which seems to parallel both investment of attention (increases in late components over frontal cortex) and withdrawal of attention (relative decreases in late components over occipital cortex). This parallel leads us to speculate that our occipital decreases may have been due to active inhibition of information-processing in the occipital regions, and that the late component enhancement over frontal areas may have been due to the mobilization of resources in these areas necessary to accomplish the tonic inhibition of visual input. … Activity in the frontal cortex apparently ‘programs’ inhibition on the specific sensory nuclei of the thalamus, in a modality specific and topographical way, accomplishing gating of sensory information to primary sensory cortex” (p. 268).

Zakrzewski, Kajetan; Szelenberger, Waldemar (1981). Visual evoked potentials in hypnosis: A longitudinal approach. International Journal of Clinical and Experimental Hypnosis, 29 (1), 77-86.

Visual Evoked Potentials (VEP’s) were recorded in 5 healthy 20-24 year-old-females during hypnosis, hypnosis after the suggestion of blindness, and in 3 waking conditions. VEP’s were recorded in these conditions 10 times within each S on different days. Both within-Ss and between-Ss analyses showed a tendency of VEP N-250 latencies (and possibly also amplitudes) to increase in hypnosis when compared to the waking state. Overall, these changes tended to be rather small. No changes were found in the earlier VEP waveform components, and some tendencies noted in the later P-300 component were largely nonsignificant. Decrease in N-250 amplitudes after the hypnotic suggestion of blindness was significant for the whole group, but was difficult to interpret, since amplitude in this condition was not significantly different from the wake control condition N-250 amplitude.
The results are considered preliminary, and a few possibilities of confirming and/or explaining them using somewhat more stringent methodology are discussed. The within-Ss approach is recommended for future studies of evoked potentials in hypnosis.

Bauer, Herbert; Berner, Peter; Steinringer, Hermann; Stacher, Georg (1980). Effects of hypnotic suggestions of sensory change on event-related cortical slow potential shifts. Archiv fur Psychologie, 133 (3), 161-169.

The purpose of this study was to evaluate whether cortical slow potentials related to a S1-S2 paradigm are influenced by hypnotic suggestions of sensory change. Five healthy subjects susceptible to hypnosis participated each in two identical experiments with three conditions. In condition (1) and (2) each three intensities of 800 and 4000 Hz tones were presented. Preceding condition (2) hypnosis was induced and the subjects received the suggestion to hear the 800 but not the 4000 Hz tones. In condition (3), the tones were presented as S1 and a flash as S2. The subjects received the same suggestions as in (2) and a motor response to S2 was required. EEG was recorded from Cz. In (1) 800 and 4000 Hz tones caused negativities of equal amplitude, in (2) only minute negativities developed, possibly due to hypnosis induced deactivation. In (3) the S1-S2 related negativities were significantly smaller in amplitude during 4000 Hz tones than during 800 Hz tones, while the negativities preceding S2 differed only after the most intense S1. Hypnotic suggestions attenuate S1-S2 related negative potentials, possibly by affecting cognitive functions.

Rizzo, Paolo Andrea; Amabile, Giuseppe; Fiumara, Romano; Caporali, Manlio; Pierelli, Francesco; Spadaro, Maria; Zanasi, Marco; Morocutti, Cristoforo (1980). Brain slow potentials and hypnosis. Biological Psychiatry, 499-506.

SUMMARY. Contingent negative variation behavior was studied in 12 voluntary normal subjects in basal conditions and in the hypnotic trance state under different emotional suggestions. A CNV voltage decrease and the appearance of a PINV were observed in the hypnotic state. Furthermore 12 nonhypnotizable control subjects were tested under the same experimental conditions and no CNV modification was found” (p. 505).

Parwatikar, Sadashiv D.; Brown, Marjorie S.; Stern, John A.; Ulett, George A.; Sletten, Ivan S. (1978). Acupuncture, hypnosis and experimental pain – I. Study with volunteers. Acupuncture and Electro-Therapeutic Research: International Journal, 3, 161-190.

An experiment was designed to evaluate the protective effects of different agents – acupuncture, hypnosis, Morphine, aspirin, Diazepam and placebo – upon experimentally-induced pain in humans. Twenty normal, healthy volunteers were subjected to cold water and tourniquet- induced pain and the protective effects of 35 minutes of hypnotic suggestion, electro- stimulation of both acupuncture points and non-acupuncture points, 10 mg/kg of Morphine, 5 grains of aspirin, 10 mg of Diazepam and a mild sugar placebo were evaluated. Data was collected on subjective evaluation of pain, EKG, EEG, respiration, skin temperature, peripheral vascular activity and EMG. A special study was also done to evaluate the effects of all the above agents on the somatosensory evoked potentials and EEG. The data were further analyzed on the basis of hypnotic susceptibility of the volunteers. The results indicated: 1) Hypnosis, acupuncture at specific sites with electrical stimulation and Morphine Sulphate had about the same reduction in experimental pain. 2) Hypnosis produced different effects from those resulting from acupuncture stimulation on EEG. 3) Acupuncture stimulation in specific loci resulted in a latency increase in the early secondary response on somatosensory evoked potential. 4) Cold water pain was remarkably reduced after true acupuncture point stimulation. 5) Tourniquet (ischemic) pain was reduced by both hypnosis and true acupuncture site stimulation. 6) Skin temperature was significantly reduced on the side of acupuncture points (true) stimulation.

Saletu, B.; Saletu, M.; Brown, M.; Stern, J.; Sletten, I.; Ulett, G. (1975). Hypno-analgesia and acupuncture analgesia: A neurophysiological reality?. Neuropsychobiology, 1, 218-242.

The effects of hypnosis, acupuncture and analgesic drugs on the subjective experience of pain and on objective neurophysiological parameters were investigated. Pain was produced by brief electric stimuli on the wrist. Pain challengers were: hypnosis (induced by two different video tapes), acupuncture (at specific and unspecific loci, with and without electrical stimulation of the needles), morphine and ketamine. Evaluation of clinical parameters included the subjective experience of pain intensity, blood pressure, pulse, temperature, psychosomatic symptoms and side effects. Neurophysiological parameters consisted of the quantitatively analyzed EEG and somatosensory evoked potential (SEP). Pain was significantly reduced by hypnosis, morphine and ketamine, but not during the control session. Of the four acupuncture techniques, only electro- acupuncture at specific loci significantly decreased pain. The EEG changes during hypnosis were dependent on the wording of the suggestion and were characterized by an increase of slow and a decrease of fast waves. Acupuncture induced just the opposite changes, which were most significant when needles were inserted at traditional specific sites and stimulated electrically. The evoked potential findings suggested that ketamine attenuates pain in the thalamo-cortical pathways, while hypnosis, acupuncture and morphine induce analgesia at the later CNS stage of stimulus processing. Finally some clinical-neurophysiological correlations were explored.

Hernandez-Peon, R.; Dittborn, J.; Borlone, M.; Davidovich, A. (1960). Changes of spinal excitability during hypnotically induced anesthesia and hyperesthesia. American Journal of Clinical Hypnosis, 3, 64. (From 21st International Congress of Physiology, Buenos Aires, 1959, pg. 124, Abstracts)

Although hypnosis is well established, the physiological mechanisms of the hypnotic state and their related sensory phenomena are far from clear. Hernandez-Peon and Donoso have found that the magnitude of photic evoked potentials in the optic radiations of awake human subjects changed in response to previous verbal suggestions concerning the intensity of the expected photic stimulus. This striking observation led the cited authors to propose that certain hypnotic sensory phenomena might be explained, at least partially, by changes occurring as far down as second-order sensory neurons by centrifugal mechanisms controlling the sensory input to the brain. In the intact subject it is impossible to record uncontaminated electrical indexes of afferent impulses from those lower sensory neurons. However, it is possible to gain indirect evidence of tactile sensory inflow to the spinal cord by recording cutaneous reflexes. In young males, a forearm skin reflex evoked by a single square pulse of 0-.1 msec. duration was recorded with cathode- ray oscilloscope. The amplitude of the evoked potentials was often reduced during the hypnotic state, and it was further reduced by verbally suggesting to the hypnotized subject complete anesthesia of the forearm. Reciprocally, during hypnotically suggested hyperesthesia the cutaneous reflex was enhanced. It is concluded that during hypnotic anesthesia and hyperesthesia excitability changes occur at the spinal level, and it is suggested that these changes probably involve the spinal internuncial system interposed between the dorsal root ganglion cells and the motoneurons. (From Abstracts, 21st Internat. Cong. Physiol., Buenos Aires, 1959, p. 124.)


Kirsch, Irving; Lynn, Steven Jay (1995). The altered state of hypnosis: Changes in the theoretical landscape. American Psychologist, 50 (10), 846-858.

Presentations of theories of hypnosis in scholarly and introductory texts portray the field as dominated by two warring camps, variously referred to as state and nonstate or as special process and social psychological. Current issues and theories in the hypnosis literature are examined. In the process, we seek to dispel the myth that hypnosis theorists can be grouped into two camps. Although there is considerable controversy about the nature of hypnosis, no issues separate all so-called special process theorists from all social psychological theorists. Instead, virtually all substantive differences between theorists cut across this apparent distinction. Furthermore, the positions taken on many of the important issues dividing the field can no longer be portrayed as simple dichotomies, such as state versus nonstate or trait versus situation. Positions on these issues can more accurately be described as points on a continuum. We conclude by drawing attention to specific questions and issues that remain unresolved.

Atkinson, Richard P. (1994). Relationships of hypnotic susceptibility to paranormal beliefs and claimed experiences: Implications for hypnotic absorption. American Journal of Clinical Hypnosis, 37, 34-40.

This study examined the relationship of hypnotic susceptibility level to belief in and claimed experience with paranormal phenomena. The Harvard … and the Inventory of Paranormal Beliefs and Experiences [developed for this study] were administered on consecutive days to 43 undergraduate students (14 men, 29 women) … . a significant multiple correlation was obtained (r = .55, p<.001). A partial correlation between hypnotic susceptibility and belief in paranormal phenomena was also significant (r = .53, p<.001), while hypnotic susceptibility was not found to be significantly related to claimed paranormal experiences. Implications of these relationships for the role of absorption in hypnosis are discussed. NOTES Discusses relationship to Absorption, and the fact that Labelle, Dixon, Laurence, & Nadon (1990) got correlation of hypnotizability with paranormal experience Martin, D.; Tomak, J.; Lynn, S. J. (1994, October). Detecting simulation with the hypnosis simulation index. [Paper] Presented at the annual meeting of the Society for Clinical and Experimental Hypnosis, San Francisco. NOTES Orne described demand characteristics of the hypnotic situation, such that some Ss want to either deceive the hypnotist or to please the hypnotist or to help the experiment work. To separate essence of hypnosis he devised an experimental technique, which informs S to role-play, and tells them intelligent Ss will be able to do this. Sheehan & McConkey note that though the model specifies subjective experience, it lacks a way of determining if people are truthful. We developed a scale assuming hypnotized Ss would be truthful and wouldn't say they had experiences they didn't, but that simulators would exaggerate. The scale included events plausibly reported by highs but not widely reported. The scale has 31 items, and is titled the Hypnotic Experience Scale. It has 24 items for experiences during hypnosis, 5 for experiences after hypnosis, and 2 for how deeply hypnotized they felt and what kind of hypnotic subject they thought they were. Ss participated in 2 sessions. They had the Harvard group scale in the first, and simulation instructions in second session. Simulation instructions were read to Low and Medium subjects. To encourage Ss to keep eyes closed, they were told it was essential to keep their eyes closed. We had scores on: Hypnosis Simulation Index SCL 90 DES Tellegen Absorption Scale Highs did not receive any simulation suggestions. Then the Stanford Scale was administered. Highs and Simulators had to pass at least 9 Harvard items. Of the predictors, only the Hypnosis Simulation Index discriminated. It correctly classified 94% of the Ss. To eliminate non-useful items, a stepwise discriminate analysis was performed. 15 items remained. These 15 items were used in a series of analyses. They discriminated between the 2 groups from 100% to 70% of the time. This study is the first to successfully discriminate hypnotized from dissimulating subjects. Simulators' performance indicate they tend to respond in stereotypic ways that exaggerate how hypnotized Ss respond. Hypnotized Ss who passed more than 10 items only rated themselves as average on hypnotizability. This has potential applications in forensic situations. 1993 Bruehl, Stephen; Carlson, Charles R.; McCubbin, James A. (1993). Two brief interventions for acute pain. Pain, 54, 29-36. This study evaluated two brief (3-5 min) interventions for controlling responses to acute pain. Eighty male subjects were randomly assigned to 1 of 2 intervention groups (Positive Emotion Induction (PEI) or Brief Relaxation (BR)) or to 1 of 2 control groups (No-instruction or Social Demand). The PEI focused on re-creating a pleasant memory, while the BR procedure involved decreasing respiration rate and positioning the body in a relaxed posture. All subjects underwent a 60-sec finger pressure pain trial. Analyses indicated that the PEI subjects reported lower ratings of pain, fear, and anxiety, and experienced greater finger temperature recovery than controls. The BR procedure resulted in greater blood pressure recovery, but did not alter ratings of pain or emotion relative to controls. Further research is needed to explore the clinical use of the PEI for acute pain management. Council, James R.; Grant, Debora L. (1993, October). Context effects: They're not just for hypnosis anymore. [Paper] Presented at the annual meeting of the Society for Clinical and Experimental Hypnosis, Arlington Heights, IL NOTES Context effects in Absorption research are found in correlations, not in mean differences. Original paper has been replicated and yet results are not always significant. Now we are trying to generalize the effect to other areas: an individually administered measure will influence other measures made in the same session. Other tests that correlate with hypnosis are studied with 2 x 2 design, enabling order effects and same vs separate contexts to be studied. Or two tests are administered at two points in time, with "bridges" between the two sessions (e.g. same experimenter, same consent forms, etc.) As one adds more and more bridging cues, the correlation of Absorption with other Tellegen MPQ subscales increases. Same context assessment increases correlation between hypnotizability and 6-8 other scales; with childhood trauma scale when trauma scale is administered first; with beliefs in paranormal phenomena when the measure is related to an adjustment scale. The same inflation of correlations was found in Beck Depression scale research. These results are of concern because we may have to re-do a lot of personality research that suggested correlation between personality test variables, as the correlations may be inflated by the effects of testing in the same context. Gearan, Paul; Kirsch, Irving (1993). Response expectancy as a mediator of hypnotizability modification: A brief communication. International Journal of Clinical and Experimental Hypnosis, 41 (2), 84-91. The role of response expectancy in bringing about increases in hypnotic susceptibility by use of the Carleton Skill Training Program (CSTP) was assessed with 27 subjects selected for their low hypnotizability scores. Subjects were randomly assigned to one of two conditions: 13 received the CSTP to increase their hypnotic susceptibility, and 14 received no training. In addition to assessing hypnotizability, hypnotic response expectancies were assessed before and after training. With pretreatment hypnotizability controlled, subjects in the training group scored significantly higher than control subjects on all self-report measures of hypnotizability but not on a measure of observed behavioral response. Changes in response expectancy were found to be highly correlated with changes in hypnotizability. With changes in expectancy controlled, no significant differences between the trained and control groups were found. Morgan, William P. (1993, October). Use of hypnosis in exercise and sport psychology. [Paper] Presented at the annual meeting of the Society for Clinical and Experimental Hypnosis, Arlington Heights, IL. NOTES Performance of exercise is rated as equal effort with hypnosis and waking conditions; but with hypnotic suggestion they will perceive it as more or less effortful (uphill exercise vs going down the hill). When they think they are going up hill both cardiac and respiratory response increase physiologically, with catecholamine differences. Mitchell (1981) suggests that respiration changes with exercise do not result from muscle feedback, but that central motor brain signals go to both the cardiovascular centers and to exercising muscle. Actually, it appears that both muscle and cortex give signals, and their synergy governs whether ventilation or heart rate increase. Wang & Morgan, Psychophysiological responses to imagined exercise, Sport Psychology Lab, University of Wisconsin-Madison. Reported that both external (watching someone else) and internal (imagining oneself) visualizing give responses similar to actual exercise. We have done research on the prediction of respiratory distress (dyspnea) - work we have done with fire fighters. The best predictor of this on treadmill with air supply is trait anxiety. Sometimes the firefighters who took off face mask even though they had air did not know why they did. It is an opportunity to use hypnotic age regression. SCUBA divers described in Lynn & Rhue also were age regressed to obtain information that was repressed. They have demonstrated stress responses like panic in a 12 foot tank also. For active people and athletes there is an "iceberg" profile on the POMS, below average on tension, depression, anger, fatigue, and confusion, but higher on vigor. But the divers who panic have a flat profile, around the 50th percentile on all POMS scales. Middleman et al used Navy divers in 25 degree C. water and used hypnosis to increase and decrease their body temperature--one of the best papers on the topic. Ss who were best able to use imagery, to think of a beach, had the poorest responses; the ones who could relax did poorest, because shivering produces heat and keeps you warm. It is opposite of what is needed. In our work, we took 5 highest and 5 lowest anxiety Ss; the latter had higher rates of respiration than the former. All Ss are similar in oxygen use whether volunteers or not. When people volunteer for research before they know hypnosis will be used, the males are lower than females [on hypnotizability?] when they finally volunteer. [He presents a lot of different tests on which volunteers do not differ from nonvolunteers personality wise.] Ikai & Steinhaus is a classic study of Disinhibition of Inhibitory Mechanisms. Taking Ss up to their maximum (in weight training) to a plateau, Ikai & Steinhaus said this is a pseudomaximum. They showed that strength increases if - you fire a starter pistol behind them - you ask them to shout just as they do it - they have alcohol - they have amphetamine sulfate - they have hypnosis It is disinhibition of the inhibitory mechanisms. [He referred to the book Mind of the Marathoner.] In Tibet an anthropologist was amazed to see a man running into their camp, and he ran straight through--a monk carrying messages. He created a non-cultic form of meditation in the laboratory (trained to visually "fix" on mountaintop, to have respiration in synchrony with locomotion, and to use a pseudo mantra "down" each time they put their foot down). Placebo condition was used also. Ss were tested by blinded lab assistants. Endurance time increased from 16 minutes to 20, while controls decreased a minute.