Hypnosis, suggestion, and placebo in the reduction of experimental pain

Two experiments compared placebo and hypnotic analgesia in high and low hypnotizable subjects. Experiment 1 demonstrated that hypnotic and placebo analgesia were equally ineffective in low hypnotizables, but that hypnotic analgesia was much more effective than placebo analgesia in high hypnotizables. Experiment 2 replicated these results, but also included low and high hypnotizables who were given a nonhypnotic suggestion for analgesia. Both the low and high hypnotizables in this group reported greater suggested than placebo analgesia and as much suggested analgesia as high hypnotizable hypnotic subjects. Both experiments found substantial discrepancies between the amount of pain reduction subjects expected from the various treatments and the amount of pain reduction they actually reported following exposure to those treatments. In Experiment 2, subjects in all treatments who reduced reported pain engaged in more cognitive coping and less catastrophizing than those who did not reduce pain. Theoretical implications are discussed.     

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.     

Effects of instructional set on attributions of nonvolition during hypnotic and nonhypnotic analgesia

Fifty highly hypnotizable subjects were assigned to four treatment groups or a no-treatment control group and then underwent two pain stimulation trials. Half the treated subjects were administered hypnotic analgesia, half waking analgesia. Within hypnotic and nonhypnotic treatments, half the subjects were given actively worded analgesia instructions, half passively worded instructions. Subjects in the four treated groups reported equivalent pain reduction and equivalent use of coping imagery, although hypnotic subjects rated themselves as more deeply hypnotized than did nonhypnotic subjects. Both hypnotic and nonhypnotic subjects given passive instructions rated their pain reduction as occurring involuntarily, whereas those given active instructions reported that their pain was reduced through their active use of coping strategies. These findings support sociocognitive formulations of hypnotic responding that view ratings of involuntariness as reflecting contextually guided interpretations of behavior.     

The role of compliance in hypnotic and nonhypnotic analgesia

We modified the standard procedure for administering finger pressure pain in order to assess the extent to which subjects biased their reports of pain reduction when exposed to compliance-inducing instructions. Experiment 1 used only highly hypnotizable subjects and found that compliance-induced reductions in reported pain were about half as large as the reported reductions produced by hypnotic analgesia suggestions. Experiment 2 used low as well as high hypnotizables and administered hypnotic or nonhypnotic analgesia instructions and compliance instructions to the same subjects on separate pain trials. Reported pain reductions produced by hypnotic and nonhypnotic analgesia suggestions and those produced by compliance instructions were substantially and significantly correlated. Furthermore, hypnotizability correlated with compliance-induced reported pain reductions as highly as it correlated with the reported reductions produced by hypnotic analgesia suggestions. Among high hypnotizables (but not low hypnotizables) compliant responding was predicted by social desirability. The findings of both studies indicate that compliance strongly influences the reports of hypnotic and nonhypnotic analgesia proffered by high hypnotizables. The role of compliance in the pain reductions reported by low hypnotizables is less clear-cut.     

Pseudomemory in hypnotized and task-motivated subjects.

Highly hypnotizable hypnotized (H; n = 16) and task-motivated (TM; n = 13) subjects received pseudomemory suggestions (see Orne, 1979). TM subjects reported being more awake and motivated than did H subjects and were more likely to pass the target noise suggestion. However, 69% of subjects in both conditions who passed the noise suggestion reported pseudomemories. Pseudomemory rate (for H subjects, 69% and for TM subjects, 46%) was not reduced by informing subjects that they could distinguish reality and fantasy in a state of deep concentration. At final inquiry, after deep concentration, pseudomemories remained stable (for H subjects, 75% and for TM subjects, 54%). As predicted, H subjects reported more unsuggested noises and more pseudomemories of novel noises than did TM subjects. Subjects who reported pseudomemories were more confident in the accuracy of their memories than were subjects who reported that the suggested noises were imagined.     

Detection of simulated hypnotic amnesia

Highly hypnotizable nonsimulators and high- and low-hypnotizable simulators of hypnosis were administered a hypnotic amnesia suggestion and tested for recall and recognition of a previously learned word list. Simulators exhibited higher levels of recall and recognition amnesia than nonsimulators. Most important, simulators recognized "forgotten" words at lower levels than expected by chance significantly more often than did nonsimulators. Implications for the detection of simulated amnesia in clinical samples are discussed.     

Hypnotic susceptibility, baseline attentional functioning, and the Stroop task

According to the theoretical framework relating hypnosis to attention, baseline attentional functioning in highly hypnotizable individuals should be more efficient than in low hypnotizable individuals. However, previous studies did not find differences in Stroop-like tasks in which the measure indicative of the Stroop interference effect was based on response latencies. This study was designed to determine whether subjects with different levels of hypnotic susceptibility show differences in baseline attentional functioning. To assess this hypothesis, high, medium, and low hypnotizable subjects performed a Stroop task designed to evaluate accuracy performance, before being subjected to hypnotic induction. Results showed that the Stroop interference effect was smaller in high hypnotizable subjects than in low hypnotizable subjects, whereas it was not different between high, and medium hypnotizable subjects. This outcome supports the notion that baseline attentional functioning is related to hypnotic susceptibility.     

Hypnotic enhancement of cognitive-behavioral interventions for pain: an analogue treatment study.

Recent meta-analyses have shown that adding hypnosis enhances the effectiveness of cognitive-behavioral psychotherapy. This hypnotic enhancement effect was evaluated in the analogue treatment of pain. Individuals scoring in the high (n = 135) and low (n = 150) ranges of hypnotic suggestibility were randomly assigned to 1 of 6 conditions: Stress Inoculation Training, the same treatment provided hypnotically, nonhypnotic analgesia suggestions, hypnotic analgesia suggestions, a hypnotic induction treatment, or a control condition. The 5 analogue treatments reduced experimental pain more than the control condition, but were not different from one another. Under circumstances optimized to detect an enhancement effect, neither Stress Inoculation Training nor analgesia suggestions produced more relief when delivered in a hypnotic context than identical treatments provided nonhypnotically.     

Hypnosis, reporting bias, and suggested negative hallucinations.

We examined the role of reporting bias in hypnotic negative hallucinations by using a paradigm in which reporting bias was assessed independently of perceptual change. In Experiment 1, highly hypnotizable subjects reported significant loudness reductions when tested for hypnotic deafness. Later, however, these subjects biased their reported loudness reductions in the absence of perceptual change, and their reporting bias scores were almost as large as their hypnotic deafness reports. Subjects also biased their ratings of strategy use. In Experiment 2, ratings of blindness given in response to a hypnotic negative visual hallucination suggestion were significantly correlated with reporting bias scores obtained in this paradigm. Although hypnotic blindness and hypnotic deafness correlated significantly, the partial correlation between these variables was nonsignificant when reporting bias scores were statistically controlled. Theoretical implications are discussed.     

Pseudomemory effects over time in the hypnotic setting

Highly (n = 36), moderately (n = 26), and low (n = 48) susceptible subjects were administered either hypnosis or waking instruction to examine the hypothesis that pseudomemory will occur for hypnotic subjects as long as 2 weeks after suggestions are given for accepting false events. Accuracy and confidence of memory were measured for all subjects, and memory was examined for free recall, structured recall, and recognition. Results indicated persistence of pseudomemory for the 2-week period for both highly and moderately susceptible subjects. Data highlighted the multifaceted operation of skill, contextual, and state instruction factors, and an hypothesis that ambiguity of communication when suggestion is delivered plays a part in the maintenance of pseudomemory over time is offered for further testing.     

Hypnotic susceptibility, visual distraction, and reports of Necker cube apparent reversals

Subjects, either susceptible (n = 50) or resistant (n = 50) to hypnotic suggestion, were asked to report on frequency of apparent reversals (ARs) to the Necker cube illusion. Such reports were made in the presence or absence of various types of visual, geometric surrounds (squares, triangles, crosses, or parallelograms). In agreement with a number of previous experiments, susceptible subjects reported perceiving more ARs than did resistant subjects. This difference held whether visual surrounds were present or absent. The presence of surrounds did serve to reduce AR reports regardless of hypnotic susceptibility level. The results are examined in terms of the ability of subjects to selectively attend when confronted with potential visual distractors.     

Hypnotizability, preference for an imagic cognitive style, and memory creation in hypnosis

We sought to extend the finding (Laurence & Perry, 1983) that it is possible through hypnosis to create a pseudomemory of a specific event. Subjects were compared on their responses to a hypnotic suggestion. We also examined the relation between nonhypnotic measures (Preference for an Imagic Cognitive Style [PICS] test and the Tellegen Absorption Scale [TAS]) and response to the suggestion. Highly (45.45%) and moderately-highly (46.15%) susceptible subjects believed that the pseudomemory was veridical, but none of the low susceptible subjects did so. Together, hypnotic susceptibility, the PICS, and their interaction more strongly predicted pseudomemory creation than any of these main effects alone. Performance on the TAS was also related to the occurrence of pseudomemory, but this relation was redundant with performance on the other measures. These results point to the complexity of the variables involved in pseudomemory creation during hypnosis.     

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.     

Gradual increase in cutaneous threshold induced by repeated hypnosis of healthy individuals and patients with atopic eczema

Gradual increase in cutaneous pain threshold was found in healthy subjects and patients with atopic eczema during repeated hypnotic sessions with specific suggestions. This increase was less in the former than in the latter group. Repeated threshold measurements did not influence the threshold. The analgesic effect outlasted the hypnotic sessions by several months. It could be, however, suddenly reduced by appropriate hypnotic suggestion.     

Posthypnotic suggestions and behavior change: Highly hypnotizables compared with simulators

The authenticity of a posthypnotically released emotion was examined to see whether this emotion also could modify the reaction times (RTs) of subjects. The simulant design proposed by Orne (1979) was utilized, with 10 highly hypnotizable subjects and 10 non-hypnotizable simulators participating in the experiment. The subjects received a post-hypnotic suggestion to the effect that every presentation of a light stimulus would release a feeling of discomfort and that a second light stimulus would be neutral. They were informed that they could terminate the stimulation by pressing a RT switch and received a suggestion of amnesia for the posthypnotic suggestion. The simulators skilfully imitated the objective behavior of the hypnotic subjects; their physiological reactions increased and their RTs were shorter when exposed to the aversive stimulation. The main differences occurred in the subjective reports. The hypnotic subjects reported that the emotion was released involuntarily and found relief in escaping from it, while the simulators reported no corresponding experiences, saying that they had deliberately manipulated the objective behavior.     

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.     

Posthypnotic amnesia for recently learned material: Interactions with “episodic” and “semantic” memory

In two experiments, posthypnotic amnesia was suggested for a word list memorized during hypnosis. After an initial test of amnesia the subjects gave word associations (Experiment 1) or category instances (Experiment 2) to stimuli intended to elicit the critical (word list) items covered by the amnesia. The extent of initial amnesia observed was strongly associated with measured hypnotic susceptibility. Even among the most hypnotizable subjects, however, the dense amnesia did not prevent the critical items from being elicited by the semantic memory tasks, nor did it modulate the priming which these associations received by virtue of the prior learning experience. Moreover, production of the critical items did not, in general, remind the amnesic subjects of those items which they had previously learned, but could not now remember. Full memory was restored after the amnesia suggestion was canceled by a prearranged cue. Posthypnotic amnesia appears to represent a temporary dissociation of episodic features from memory traces, so that the subject has difficulty in reconstructing the context in which the target events occurred.     

Individual differences in afterimage persistence: relationships to hypnotic susceptibility and visuospatial skills.

To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images.     

Reality versus suggestion: pseudomemory in hypnotizable and simulating subjects

Assigned hypnotizable (N = 56) and simulating Ss (N = 44) to 1 of 4 conditions: heard a phone ring and conversation, received a suggestion to hear a phone ring and conversation, received a suggestion and heard a phone ring and conversation, or neither heard a phone nor received a suggestion. Hypnotizable Ss successfully discriminated objective events from suggested sources of input. When Ss received a suggestion to hear a phone ring, only 11.5% indicated it actually rang in their open-ended reports; in response to a forced-choice question, none did so. In spontaneous reports, none of the hypnotizable Ss who heard a phone ring indicated it was suggested; only one did so in response to a forced-choice item (vs. 2 simulators). In the no-phone/no-suggestion condition, more simulators than hypnotizable Ss indicated that a phone rang or was suggested.     

认知神经科学视角的催眠研究述评

催眠被广泛的应用在临床心理治疗中, 但是, 关于催眠方面的研究却相当匮乏, 而且相当模糊。近年来, 随着fMRI, ERP和PET等技术的引入, 我们对催眠引导和催眠暗示有了更加深入的理解。对于疼痛和幻觉的研究表明, 至少对于高暗示性被试而言, 催眠暗示可以引起与真实刺激同样的大脑皮层的激活; 而催眠后暗示对于注意策略的调控, 可以使原有的认知过程发生改变, 其中之一是使用催眠后暗示来抑制“Stroop效应”语义加工过程; 催眠后遗忘更是实现了内隐记忆和外显记忆遗忘的分离。未来研究者将继续从探讨催眠本身的神经属性和催眠暗示所引起的认知过程的改变两个角度去认识催眠, 揭开催眠的实质。