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.     

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.     

Hypnotizability and automaticity: toward a parallel distributed processing model of hypnotic responding

We tested a hypothesis from parallel distributed processing theory that highly hypnotizable subjects have greater connection strengths along verbal pathways and would show greater Stroop effects than low hypnotizable subjects. Using Cheesman & Merikle's (1986) paradigm, which varied cue visibility and probability, we assessed automatic and strategic effects on Stroop performance. Compared with 9 low and 9 moderately hypnotizable subjects, 9 highly hypnotizable ones showed significantly greater Stroop effects for both visible- and degraded-word trials. No strategic differences emerged for the 3 hypnotizability groups. These findings support the contention that highly hypnotizable persons have stronger verbal connection strengths than their moderately and low susceptible counterparts, and they may account for highly hypnotizable persons' propensity to disregard personal attributions and label their responses in hypnosis as being involuntary.     

焦虑个体“冷”、“热”执行功能Stroop效应量比较

该文采用Stroop实验范式对筛选出的49名高焦虑个体和48名低焦虑个体的“冷”、“热”执行功能进行测量,以探讨不同焦虑程度个体“冷”、“热”执行功能间的差异。结果表明,在“冷”执行功能方面,高焦虑个体与低焦虑个体Stroop效应量之间没有显著差异;在“热”执行功能方面,两组被试情绪Stroop的效应量无差异;两类词;12的Stroop效应量差异显著;词汇类型×被试类型的交互作用非常显著;进一步的简单效应分析表明,两组被试的情绪Stroop效应量在消极词汇水平差异显著,两类词汇Stroop效应量在低焦虑组差异显著。说明高、低焦虑个体在“冷”执行功能上没有显著差异,高焦虑个体的“冷”执行功能正常,而“热”执行功能下降,表现为高焦虑个体对两极情绪的趋避关系失调,即对消极情绪具有偏向性,对积极情绪具有回避性。     

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.     

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.     

Attentional bias and anxiety in individuals with coronary heart disease

This study examined whether in an emotional Stroop task, individuals with coronary heart disease (CHD) would show greater attention towards the threatening words related to their disease than healthy persons, and if such an attentional bias is associated with anxiety. An emotional Stroop task with threatening words related to CHD as well as positive, negative and neutral words was administered to 35 individuals with CHD and 35 healthy controls. Additionally, the original Stroop task, the Beck anxiety inventory and the state-trait anxiety inventory were administered. The results indicated an attentional bias towards threatening words related to CHD in the individuals with CHD. They experienced higher interference than healthy participants from threatening words related to CHD but not from positive or negative words. Moreover, the level of interference was associated with their level of anxiety, and a vicious circle may exist in this association. In addition, results indicated a possible deficit of executive functioning among individuals with CHD. Attentional bias, as well as its association with anxiety, and an indication of deficit in executive functioning among individuals with CHD might be the risk factors for these individuals’ quality of life and for further development of their disease.     

Suggestion overrides the Stroop effect in highly hypnotizable individuals

Cognitive scientists distinguish between automatic and controlled mental processes. Automatic processes are either innately involuntary or become automatized through extensive practice. For example, reading words is a purportedly automatic process for proficient readers and the Stroop effect is consequently considered the "gold standard" of automated performance. Although the question of whether it is possible to regain control over an automatic process is mostly unasked, we provide compelling data showing that posthypnotic suggestion reduced and even removed Stroop interference in highly hypnotizable individuals. Drawing on a large sample of highly hypnotizable participants, we examined the effects of suggestion on Stroop performance both with and without a posthypnotic suggestion to perceive the input stream as meaningless symbols. We show that suggestion administered to highly hypnotizable persons significantly reduced Stroop interference and derailed a seemingly automatic process.     

Attentional focus, processing load, and Stroop interference

Although the effects of attentional focus and perceptual load on selective attention when targets and distractors are distinct objects that occupy separate locations are well known, there has been little examination of their role when both relevant and irrelevant information pertains to the same object. In four experiments, participants were shown Stroop color words or strings of letters in a task of speeded color identification. When the participants' attentional focus was manipulated via cue validity or precue size, greater Stroop interference was observed when the attentional focus was narrow than when it was broad. However, when the participants were induced to adopt a comparable attentional focus in a dual-task paradigm, the differential Stroop interference was eliminated. Furthermore, contrary to the prediction of the perceptual load hypothesis, different levels of processing load did not lead to differential Stroop interference. These results emphasize the importance of stimulus structure in understanding distractor processing. They indicate that when relevant and irrelevant information pertains to the same object, narrowing attentional focus increases distractor processing, and perceptual load has a negligible effect on the extent of distractor processing.     

Abstracts

Two studies were designed to establish whether high anxiety sensitive (AS) university students selectively process threat cues pertaining to their feared catastrophic consequences of anxiety, and to examine potential gender differences in the selective processing of such threat cues among high versus low AS subjects. Forty students (20 M; 20 F) participated in Study 1. Half were high AS and half low AS, according to scores on the Anxiety Sensitivity Index (ASI). Subjects completed a computerised Stroop colournaming task involving social/psychological threat (e.g. EMBARRASS; CRAZY), physical threat (e.g. CORONARY; SUFFOCATED), and neutral (e.g. MOTEL; TOWEL) target words. High AS subjects demonstrated more threat-related interference in colour-naming than did low AS subjects, overall. High AS menevidencedgreater interference relative to low AS men only for the social/psychological threat stimuli; highAS women evidencedgreater interference relative to low AS women only for the physical threat stimuli. Study 2 was designed to replicate and extend the novel Study 1 finding of a cognitive bias favouring the processing of social/psychological threat cues among high AS men. Participants were 20 male university students (10 high AS; 10 low AS). In addition to social/psychological threat, physical threat, and neutral words, a category of positive emotional words (e.g. HAPPINESS; CELEBRATION) was included as a supplementary control on the Stroop. Consistent with Study 1, high AS males evidenced greater Stroop interference than did low AS males, but only for social/psychological threat words. No AS group differences in Stroop interference were revealed for the physical threat or positive words. Clinical implications, and potential theoretical explanations for the gender differences, are discussed.     

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.     

材料类型和颜色典型性影响颜色-物体Stroop效应

通过两个实验考查材料类型和颜色典型性对颜色-物体Stroop效应的影响。实验1,考查颜色-物体（图片）Stroop效应。结果颜色典型性差异显著,命名图片的颜色和图片的名称都产生显著的颜色-物体Stroop效应。实验2,考查颜色-物体（词语）Stroop效应。结果颜色典型性差异显著,命名词语的颜色产生颜色-物体Stroop效应,命名词语的名称未产生颜色-物体Stroop效应。结论,材料类型和颜色典型性影响颜色-物体Stroop效应。     

Reflections on the varieties of hypnotizables: A commentary on Terhune and Cardeña

This commentary reflects on the varieties of high hypnotizable subjects suggested in the works by Barber, Barrett, Pekala and colleagues, and Terhune and Cardeña (2010). These different studies point to the existence of different types of low, medium, and high hypnotizable subjects. However, types of high hypnotizables have received the most attention. Two main concerns are raised in this commentary: (a) drawing parallels between the suggested typologies is not without problems given methodological differences among different studies, and (b) the low base rates of these special types is likely not to appeal to a typical clinician, already resistant to testing for hypnotizability, to conduct initial assessments so as to tailor suggestion to fit specific typologies.     

Stress reduces attention to irrelevant information: Evidence from the Stroop task

Stroop interference can be reduced by stress, and this has been taken as evidence that stress decreases the attention paid to irrelevant information, a theory known as ‘Easterbrook’s hypothesis’. This contradicts more recent theories, which state that attentional control deteriorates in stress. Fifty-five participants undertook a Stroop task under high stress (loud white noise) and low stress conditions. Attention to the irrelevant word information was assessed by manipulating the proportion of congruent trials (e.g. the word RED in the colour red); it is known that Stroop interference increases when many such trials are presented. This effect was reduced when participants were stressed, which is evidence that stress does indeed reduce attention to irrelevant information. This pattern of results was not present in participants with low working memory spans, presumably because these participants had less attentional control. These findings highlight an important weakness in contemporary theories of cognition in stress.     

Patterns of hypnotic response,revisited

It has long been speculated that there are discrete patterns of responsiveness to hypnotic suggestions, perhaps paralleling the factor structure of hypnotizability. An earlier study by Brenneman and Kihlstrom (1986), employing cluster analysis, found evidence for 12 such profiles. A new study by Terhune (2015), employing latent profile analysis, found evidence for three such patterns among highly hypnotizable subjects, and a fourth comprising subjects of medium hypnotizability. Some differences between the two studies are described. Convincing identification of discrete “types” of high hypnotizability, such as dissociative and nondissociative, may require a larger dataset than is currently available, but also data pertaining directly to divisions in conscious awareness and experienced involuntariness.     

Ageing and bilingualism: absence of a "bilingual advantage" in stroop interference in a nonimmigrant sample

Previous research has found an advantage for bilinguals relative to monolinguals on tasks of attentional control. This advantage has been found to be larger in older adults than in young adults, suggesting that bilingualism provides a buffer against age-related declines in executive functioning. Using a computerized Stroop task in a nonimmigrant sample of young and older monolinguals and bilinguals, the current investigation tried to replicate previous findings of a bilingual advantage. A bilingual advantage would have been demonstrated by smaller Stroop interference (i.e., smaller increases in response time for incongruent than for neutral trials) for bilinguals than for monolinguals. The results showed that bilingual young adults showed a general speed advantage relative to their monolingual counterparts, but this was not associated with smaller Stroop interference. Older adults showed no effect of bilingualism. Thus, the present investigation does not find evidence of a bilingual advantage in young or older adults and suggests limits to the robustness and/or specificity of previous findings.     

Impact of a brief auditory attention training on a modified colour-word Stroop task in a high anxiety and worry sample

Poor attentional control leads to attentional biases that are implicated in psychological distress. Attention Training Technique (ATT) is an auditory intervention designed to strengthen attentional control. Research indicates that ATT alleviates anxiety and depressive symptoms. This study is a randomised control trial with repeated measures that tested if a lab-based, single-exposure of ATT strengthened attentional control. Forty-six nonclinical, high anxiety/worry participants received either ATT or a sham control intervention. Attentional control was assessed using the standard and a modified version of the colour-word Stroop task. The modified version incorporated tactile interference to increase perceptual load. A series of mixed effects models, simple contrasts, and z-tests were used to evaluate if cross-modal interference worsened, and whether ATT was beneficial to, attentional control. Tactile interference increased reaction times but, when Stroop interference was controlled for, this was only true on incongruent trials. The impact of ATT was greatest under high perceptual load.     

Dissociative Tendencies, Attention, and Memory

Two groups of college students were selected on the basis of their scores on the Dissociative Experiences Scale (DES). The high-DES group (score > 20, M = 29.6; n = 54) and low-DES group (score < 10, M = 5.1; n = 54) both completed the standard and a new dual-task version of the Stroop ink-naming task with xs (baseline condition) and color, neutral, and emotionally charged words. Free recall results indicated that high-DES participants remembered fewer emotionally charged words than low-DES participants. We found a crossover interaction for Stroop interference: High-DES participants showed more interference (conflicting color — baseline latency for ink naming) in a selective-attention Stroop task and less interference in the dual-task Stroop task. The interaction between attentional context and dissociation for Stroop interference and the free recall results are consistent with a cognitive-environments view of dissociative tendencies. In this view, dissociative tendencies, which have been otherwise speculated to be largely deleterious, can be advantageous in certain contexts.     

Does anxiety lead to selective processing of threat-related information?

Four experiments investigating the detailed nature of the attentional bias in anxiety are reported. Previous research using the Stroop task has shown that, when compared with non-patient controls, anxious patients are relatively slower at colour naming threat-related words than non-threat words. Experiments One and Two investigated whether this apparent attentional bias is a function of anxiety per se and/or is related to patient/non-patient status. Experiment One compared colour-naming times for threat and non-threat words in low, medium and high trait anxiety normal subjects. High anxiety was not associated with slower colour-naming times for threat words. Experiment Two compared generalized anxiety disorder patients with equally anxious non-patients and found that the patients were significantly slower at colour-naming threat words. Read aloud and dwell tasks were also included in these experiments in order to identify the mechanism of Stroop interference. Experiments Three and Four investigated whether anxious patients' attentional bias is specific to threat-related material or also extends to certain positive, emotional material. In Experiment Three words used in previous Stroop studies were rated for emotionality. Threat words were more emotional, as well as more threatening, than control words, indicating that previous studies have confounded threat and emotionality. Experiment Four compared colour-naming times for threat words, equally emotional positive words, and neutral words. Consistent with the emotionality hypothesis, generalized anxiety disorder patients were slower than non-anxious controls at colour naming both threat words and positive words. The theoretical, methodological and clinical implications of these results are discussed.     

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.