Hypnotic suggestion modulates cognitive conflict: the case of the flanker compatibility effect

The present work was aimed at investigating whether the flanker compatibility effect can be eliminated by means of a posthypnotic suggestion influencing attentional focusing. In Experiment 1, participants who scored high and low on hypnotic susceptibility performed the flanker compatibility task when naturally awake and when under a posthypnotic suggestion aimed at increasing the target's discriminability from the flankers. Results showed that the posthypnotic suggestion effectively eliminated the flanker compatibility effect in highly susceptible participants, whereas low-susceptibility participants did not show any reduction in the effect. In Experiment 2, highly susceptible participants performed the task after receiving a suggestion but without the induction of hypnosis. Results showed that the suggestion alone was not sufficient to reduce the flanker compatibility effect. These results support the view that in highly susceptible participants, hypnotic suggestion can influence the ability to focus on relevant information.     

Posthypnotic suggestion and the modulation of Stroop interference under cycloplegia

Recent data indicate that under a specific posthypnotic suggestion to circumvent reading, highly suggestible subjects successfully eliminated the Stroop interference effect. The present study examined whether an optical explanation (e.g., visual blurring or looking away) could account for this finding. Using cyclopentolate hydrochloride eye drops to pharmacologically prevent visual accommodation in all subjects, behavioral Stroop data were collected from six highly hypnotizables and six less suggestibles using an optical setup that guaranteed either sharply focused or blurred vision. The highly suggestibles performed the Stroop task when naturally vigilant, under posthypnotic suggestion not to read, and while visually blurred; the less suggestibles ran naturally vigilant, while looking away, and while visually blurred. Although visual accommodation was precluded for all subjects, posthypnotic suggestion effectively eliminated Stroop interference and was comparable to looking away in controls. These data strengthen the view that Stroop interference is neither robust nor inevitable and support the hypothesis that posthypnotic suggestion may exert a top-down influence on neural processing.     

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.     

Hypnotically induced emotional numbing: a real-simulating analysis

This study compared 20 real, hypnotized and 20 simulating, unhypnotized participants who were administered a hypnotic induction and then presented with emotionally distressing and neutral visual images. Half were administered a hypnotic suggestion for emotional numbing. Reals and simulators who received the emotional numbing suggestion reported comparably less responsivity to distressing stimuli than others. Whereas emotionally numb reals displayed little change in electromyographic (EMG) activity during the distressing stimuli, simulators displayed marked reduction in EMG activity. Reals (not simulators) displayed a dissociation between their affective response and awareness of the negative content of the stimuli following the numbing suggestion.     

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

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

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 pseudomemories,prehypnotic warnings,and the malleability of suggested memories

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

Temporal constraints of the word blindness posthypnotic suggestion on Stroop task performance

The present work investigated possible temporal constraints on the posthypnotic word blindness suggestion effect. In a completely within-subjects and counterbalanced design 19 highly suggestible individuals performed the Stroop task both with and without a posthypnotic suggestion that they would be unable to read the word dimension of the Stroop stimulus, both when response-stimulus interval (RSI) was short (500 ms) or equivalent to previous studies (3500 ms). The suggestion reduced Stroop interference in the short RSI condition (54 vs. 6 ms) but not in the long RSI condition (52 vs. 56 ms), and did not affect Stroop facilitation. Our results suggest that response to the suggestion involves reactive top-down control processes that persist only if levels of activation can be maintained. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Posthypnotic Responding Away from the Hypnotic Setting

We examined posthypnotic suggestion away from the laboratory. In Experiment 1, high-hypnotizable subjects were given a posthypnotic suggestion (of limited or unlimited duration) or a social request (of unlimited duration) to mail one postcard every day to the experimenter. Subjects given a social request rather than a posthypnotic suggestion sent more postcards, and those given a limited-duration suggestion responded differently from those given an unlimited-duration suggestion. In Experiment 2, real, hypnotized and simulating, unhypnotized subjects were given a posthypnotic suggestion, and nonhypnotic control subjects were given a social request, to mail one postcard every day; the suggestion or request was of either limited or unlimited duration. Real, hypnotized subjects sent more postcards than simulators; control subjects sent as many postcards as real, hypnotized subjects; and subjects given a suggestion or request of limited duration sent more than those given one of unlimited duration. The findings highlight the interaction of individual differences and the social context of the suggestion or request. They underscore important aspects of experience and behavior associated with posthypnotic responding away from the hypnotic setting.     

Investigating the stability of and relationships among global/local processing measures

Global/local stimuli have been used to estimate global processing biases in individuals and groups, as well as in response to various manipulations. Throughout the literature, multiple different versions of global/local stimuli have been used, such as traditional hierarchical letters and numbers (i.e., Navon letters), abstract hierarchical shapes, and high- and low-spatial-frequency gratings and faces. However, currently it is unclear how reliable or stable performance is on these measures within individuals over time, and whether these seemingly different measures are tapping into the same underlying process. As such, the purpose of the present study was to examine the stability of individual performance on three distinct global/local measures over time and to examine the relationships among the measures. In two studies, we examined the reliability of the biases within, and the relationships among, standard Navon letters in a traditional interference task, hierarchical shapes in a forced choice task, and superimposed high- and low-pass spatial frequency faces in a forced choice task. In both studies, participants completed all three of the tasks, and then returned 7–10 days later to again complete the same tasks. The degree of global/local bias within an individual was found to be highly reliable in the hierarchical shape task and the spatial frequency face task, but less reliable in the traditional Navon letter task. Interestingly, in both studies we found that none of the three measures of global bias were related to each other. Therefore, while these measures do appear to be reliable over time, they may be tapping into distinct aspects of global/local processing.     

Working memory and stroop interference: an individual differences investigation

We investigated the claim that individual differences in working-memory capacity reflect limitations on the ability to inhibit task-irrelevant information and/or to maintain activation in the face of distracting or interfering events. Specifically, we investigated whether high- and low-capacity individuals differed in their susceptibility to interference on the Stroop task and whether high-capacity individuals employed a strategy for minimizing Stroop interference. In Experiment 1, we found that high-capacity participants showed substantial interference when conflict trials were infrequent, but almost no interference when conflict trials were frequent. In contrast, low-capacity participants showed substantial interference irrespective of the proportion of conflict trials. In Experiment 2, we found that high-capacity participants experienced substantial negative priming, slow responses when the to-be-named color was the irrelevant word on the previous trial. We discuss these results and their implications for high-capacity individuals' ability to reduce Stroop interference in light of both inhibitory and noninhibitory accounts of negative priming.     

SNARC for numerosities is modulated by comparative instruction (and resembles some non-numerical effects)

The spatial–numerical association of response codes (SNARC) effect is observed for both numerical (Arabic digits) and non-numerical stimuli (size, duration, height). However, in a context of comparative judgment, Arabic numbers are mapped onto space differently from sizes and heights: SNARC for Arabic digits is formed consistently in a certain cultural reading direction, whereas SNARC for sizes and heights is additionally modulated by comparative instruction (it reverses when participants choose larger magnitudes). In the present study, we test whether the spatial characteristic of magnitude processing revealed in a context of comparison is determined by a presence or lack of numerical content of the processed information, or it depends on specific directional experience (e.g., left-to-right ordering) associated with the processed magnitude format. We examine the SNARC effect with the pairwise comparison design, by using non-symbolic numerical stimuli (objects’ collections), for which the left-to-right spatial structure is not as exceedingly overlearned as for Arabic numbers. We asked participants from two reading cultures (left-to-right vs. mixed reading culture) to compare numerosities of two sets, choosing either a larger or smaller one. SNARC emerged in both groups. Additionally, it was modulated by comparative instruction: It appeared in a left-to-right direction when participants selected a smaller set, but it tended to reverse when participants selected a larger set. We conclude that spatial processing of numerosities is dissociated from spatial processing of Arabic numbers, at least in a context of comparative judgment. This dissociation could reflect differences in spatial ordering experience specific to a certain numerical input.     

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.     

Auditory local bias and reduced global interference in autism

Processing local elements of hierarchical patterns at a superior level and independently from an intact global influence is a well-established characteristic of autistic visual perception. However, whether this confirmed finding has an equivalent in the auditory modality is still unknown. To fill this gap, 18 autistics and 18 typical participants completed a melodic decision task where global and local level information can be congruent or incongruent. While focusing either on the global (melody) or local level (group of notes) of hierarchical auditory stimuli, participants have to decide whether the focused level is rising or falling. Autistics showed intact global processing, a superior performance when processing local elements and a reduced global-to-local interference compared to typical participants. These results are the first to demonstrate that autistic processing of auditory hierarchical stimuli closely parallels processing of visual hierarchical stimuli. When analyzing complex auditory information, autistic participants present a local bias and a more autonomous local processing, but not to the detriment of global processing.     

Adaptation to (non)valent task disturbance

The cognitive system adapts to disturbances caused by task-irrelevant information. For example, interference due to irrelevant spatial stimulation (e.g., the spatial Simon effect) typically diminishes right after a spatially incongruent event. These adaptation effects reflect processes that help to overcome the impact of task-irrelevant information. Interference with (or interruption of) task processing can also result from valent (i.e., positive or negative) stimuli, such as in the ??affective Simon?? task. In the present study, we tested whether the resolution of valence-based task disturbances generalizes to the resolution of other cognitive (spatial) types of interference, and vice versa. Experiments 1 and 2 explored the interplay of adaptation effects triggered by spatial and affective interference. Incongruent spatial information modified the spatial Simon effect but not affective interference effects, whereas incongruent affective information modified affective interference effects to some extent, but not spatial Simon effects. In Experiment 3, we investigated the interplay of adaptation effects triggered by spatial interference and by the interruption of task processing from valent information that did not overlap with the main task (??emotional Stroop?? effect). Again we observed domain-specific adaptation for the spatial Simon effect but found no evidence for cross-domain modulations. We assume that the processes used to resolve task disturbance from irrelevant affective and spatial information operate in largely independent manners.     

Absorbed in thought: the effect of mind wandering on the processing of relevant and irrelevant events

This study used event-related potentials to explore whether mind wandering (task-unrelated thought, or TUT) emerges through general problems in distraction, deficits of task-relevant processing (the executive-function view), or a general reduction in attention to external events regardless of their relevance (the decoupling hypothesis). Twenty-five participants performed a visual oddball task, in which they were required to differentiate between a rare target stimulus (to measure task-relevant processes), a rare novel stimulus (to measure distractor processing), and a frequent nontarget stimulus. TUT was measured immediately following task performance using a validated retrospective measure. High levels of TUT were associated with a reduction in cortical processing of task-relevant events and distractor stimuli. These data contradict the suggestion that mind wandering is associated with distraction problems or specific deficits in task-relevant processes. Instead, the data are consistent with the decoupling hypothesis: that TUT dampens the processing of sensory information irrespective of that information's task relevance.     

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

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

Temporal preparation facilitates perceptual identification of letters

Recent evidence has suggested that perceptual processing of single stimulus features improves when participants are temporally prepared for the occurrence of the stimuli. This study was conducted to investigate whether the benefit of temporal preparation generalizes to perceptual identification of more complex stimuli, such as letters. In three experiments, participants discriminated masked letters under high- and low-temporal-preparation conditions. Visual discrimination performance in all experiments improved when the participants were temporally prepared. Therefore, the present results support the notion that perception benefits from temporal preparation not only at the feature level, but also at subsequent levels at which feature information is integrated.     

Suggested visual hallucinations in and out of hypnosis

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

Hypnotic ingroup-outgroup suggestion influences economic decision-making in an Ultimatum Game

Studies in economic decision-making have demonstrated that individuals appreciate social values supporting equity and disapprove unfairness when distributing goods between two or more parties. However, this seems to critically depend on psychological mechanisms partly pertaining to the ingroup-outgroup distinction. Little is known as to what extent economic bargaining can be manipulated by means of psychological interventions such has hypnosis. Here we show that a hypnotic ingroup versus outgroup suggestion impacts the tolerance of unfairness in an Ultimatum Game. Specifically, the ingroup suggestion was associated with significantly greater acceptance rates of unfair offers than the outgroup suggestion, whereas hypnosis alone exerted only small effects on unfairness tolerance. These findings indicate that psychological interventions such as hypnotic suggestion can contribute to ingroup favoritism and outgroup rejection.