Hypnotic blindness: a behavioral and experiential analysis

This research examined the influence of visual information on a decision task that subjects were administered during hypnotically suggested blindness. Real, hypnotizable subjects and simulating, unhypnotizable subjects were tested in two experiments. Experiment 1 focused on behavioral responses, and Experiment 2 focused on experiential reactions. In both experiments, the findings indicated that the behavioral responses of reals were influenced by visual information despite their reported blindness. The behavioral responses of reals and simulators were essentially similar. The experiential data in Experiment 2 provided information about the phenomenal nature of subjects' reported blindness. The experimental reactions of reals and simulators were essentially different. The research is discussed in terms of the issues that need to be considered in the development of a model of hypnotic blindness.     

Hypnotic blindness and the relevance of cognitive style

Real, hypnotized and simulating, unhypnotized subjects were instructed to use either a constructive or a concentrative cognitive style when attempting to respond to a suggestion for hypnotic blindness; also, some subjects were administered the suggestion without any instructions about cognitive style. More reals who received the constructive rather than the concentrative instructions reported complete blindness; a similar number of simulators who received the different instructions reported complete blindness. Moreover, reals who received the constructive instruction reported a more rapidly developed belief in their blindness. The findings are discussed in terms of the relevance of cognitive style to subjects' reports of hypnotic blindness, and the possibility is considered that both reports of and belief in hypnotic blindness are determined in part by cognitive style.     

Dissociating spatial attention and awareness in emotion-induced blindness

Emotional stimuli attract spatial attention, sometimes improving perception at their location. But they also can disrupt awareness of targets at their location, a phenomenon known as emotion-induced blindness. Such discrepant findings might reflect the impact of emotional stimuli on different perception mechanisms. We dissociated spatial attention and awareness by investigating the spatial distribution of emotion-induced blindness. Participants searched for a target within two simultaneous rapid streams of pictures, one of which could also contain a preceding emotional distractor. When targets were followed by additional stream items, emotion-induced blindness occurred only at the location of the distractor. However, when no items appeared after the target, so that it could persist in iconic memory and its temporal position was easily discernible, emotional disruption of target perception was more robust away from the distractor's location than at the distractor's location. The results suggest that although emotional distractors attract spatial attention, they inhibit identification of competing items potentially linked to the same spatiotemporal position.     

Repetition blindness in rapid lists: activation and inhibition versus construction and attribution

The authors examine the repetition blindness effect--the failure to report one of the occurrences of a word presented twice in a rapid list. This phenomenon has been ascribed to inhibitory processes that prevent immediate tokenization of the 2nd occurrence of a repeated word. The authors present several kinds of evidence against that account, including observations that repetition blindness (a) does not occur when repetitions are not embedded in a list of familiar orthographic units, (b) is alleviated by precuing the subject with the identity of the word that may repeat within a rapid list, and (c) can be caused by cues presented after the list, when the opportunity for inhibition has passed. It is proposed that repetition blindness can better be understood through the principles of construction and attribution.     

Dissociation of processing time and awareness by the inattentional blindness paradigm

Consciousness researchers are interested in distinguishing between mental activity that occurs with and without awareness (i.e., explicit versus implicit processes). The inattentional blindness (IB) paradigm is an excellent tool for this question because it permits the independent manipulation of processing time and awareness. In the present study, we show that implicit texture segregation can occur during inattentional blindness, provided that the texture is exposed for a sufficient duration. In contrast, a Simon effect does not occur during inattentional blindness, even with similar exposure duration of the critical stimulus. This reveals a dissociation between processing time and awareness, consistent with the possibility of separate processing streams for explicit and implicit visual perception.     

Preceding stimulus awareness augments offset-evoked potentials: Evidence from motion-induced blindness

Event-related potentials (ERPs) were measured in response to the objective offset of a visual disk under two physically similar conditions: (1) visible conditions in which the target disk was well perceived and (2) invisible conditions in which participants reported to have not seen the target because of motion-induced blindness (Bonneh, Cooperman, & Sagi in Nature 411:798-801, 2001). Electrophysiological responses to the physical offset of the target disk were almost completely absent in the invisible conditions (Experiment 2). In the same conditions, the physical offset was almost completely invisible (Experiment 1). Results suggest an augmenting function of prior awareness of a stimulus for the offset-triggered ERP of that stimulus.     

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.     

Hypnotic suggestibility,cognitive inhibition,and dissociation

We examined two potential correlates of hypnotic suggestibility: dissociation and cognitive inhibition. Dissociation is the foundation of two of the major theories of hypnosis and other theories commonly postulate that hypnotic responding is a result of attentional abilities (including inhibition). Participants were administered the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C. Under the guise of an unrelated study, 180 of these participants also completed: a version of the Dissociative Experiences Scale that is normally distributed in non-clinical populations; a latent inhibition task, a spatial negative priming task, and a memory task designed to measure negative priming. The data ruled out even moderate correlations between hypnotic suggestibility and all the measures of dissociation and cognitive inhibition overall, though they also indicated gender differences. The results are a challenge for existing theories of hypnosis.     

Imaging,empathy, and causal attribution

Three studies were conducted to test whether imagery accounts for the effects of empathy on attributions, that is, whether attributers construct and scan a mental image of social scenarios the same way that actual participants scan a real environment. According to this interpretation, attributers “see” the world as the participant does and make vicarious attributions. An alternative interpretation holds that subjects base vicarious attributions on recreating the motivations and affect of the actor, so that imaging is irrelevant to empathy and attributions. In the first study, subjects who imagined a story from the perspective of a particular character later showed differential recall of story details as a function of role, but not differential attributions. In Experiment 2, role-taking subjects showed clear effects of imaged perspective on recall for story details, but no effects on attributions of causality for an accident. Further, recall and attribution were uncorrelated. In the last study, empathy and imagery role-taking instructions produced independent effects: imagers showed pronounced perspective-relevant recall and empathizers did not. Neither showed unambiguous vicarious attributions. Recall and attribution were again uncorrelated. These studies suggest that the imagery explanation of empathy effects is untenable, and imply that the recall of perspective-relevant details is unlikely to mediate attributions of causality in imaginary scenarios.     

Frustration,attribution of blame,and aggression

In contrast to most recent studies of human aggression, multiple measures of naturally occurring aggressive behavior were examined in a realistic and involving setting. Consistent with attributional formulations, it was found that aggression increased in accord with attributions of blame, and that more blame was attributed to another in response to inadequately justified thwartings than to adequately justified thwartings. As anticipated, anger, other-directed attributions of blame, and other-directed aggression were greatest in response to unjustified (illegitimate) thwartings. Justified (legitimate) thwartings produced intermediate anger and intermediate levels of blame and aggression internally and externally. Self-caused (internal) thwartings, ostensibly caused neither by the other's disposition nor by situational factors, produced the least anger and other-directed aggression but the most self-blame/self-aggression. In addition, unexpected thwartings produced independently more anger than did expected thwartings, and high-drive thwartings produced independently less other-directed aggression than did low-drive thwartings. The results are discussed with reference to both the need and the potential for studies of human aggression which employ more ecologically valid settings and measures of aggressive behavior.     

What you see is what you set: sustained inattentional blindness and the capture of awareness

This article reports a theoretical and experimental attempt to relate and contrast 2 traditionally separate research programs: inattentional blindness and attention capture. Inattentional blindness refers to failures to notice unexpected objects and events when attention is otherwise engaged. Attention capture research has traditionally used implicit indices (e.g., response times) to investigate automatic shifts of attention. Because attention capture usually measures performance whereas inattentional blindness measures awareness, the 2 fields have existed side by side with no shared theoretical framework. Here, the authors propose a theoretical unification, adapting several important effects from the attention capture literature to the context of sustained inattentional blindness. Although some stimulus properties can influence noticing of unexpected objects, the most influential factor affecting noticing is a person's own attentional goals. The authors conclude that many--but not all--aspects of attention capture apply to inattentional blindness but that these 2 classes of phenomena remain importantly distinct.     

Mental imagery, reasoning, and blindness

Although reasoning seems to be inextricably linked to seeing in the “mind's eye”, the evidence is equivocal. In three experiments, sighted, blindfolded sighted, and congenitally totally blind persons solved deductive inferences based on three sorts of relation: (a) visuo-spatial relations that are easy to envisage either visually or spatially, (b) visual relations that are easy to envisage visually but hard to envisage spatially, and (c) control relations that are hard to envisage both visually and spatially. In absolute terms, congenitally totally blind persons performed less accurately and more slowly than the sighted on all such tasks. In relative terms, however, the visual relations in comparison with control relations impeded the reasoning of sighted and blindfolded participants, whereas congenitally totally blind participants performed the same with the different sorts of relation. We conclude that mental images containing visual details that are irrelevant to an inference can even impede the process of reasoning. Persons who are blind from birth—and who thus do not tend to construct visual mental images—are immune to this visual-impedance effect.     

Mental imagery,reasoning, and blindness

Although reasoning seems to be inextricably linked to seeing in the “mind's eye”, the evidence is equivocal. In three experiments, sighted, blindfolded sighted, and congenitally totally blind persons solved deductive inferences based on three sorts of relation: (a) visuo-spatial relations that are easy to envisage either visually or spatially, (b) visual relations that are easy to envisage visually but hard to envisage spatially, and (c) control relations that are hard to envisage both visually and spatially. In absolute terms, congenitally totally blind persons performed less accurately and more slowly than the sighted on all such tasks. In relative terms, however, the visual relations in comparison with control relations impeded the reasoning of sighted and blindfolded participants, whereas congenitally totally blind participants performed the same with the different sorts of relation. We conclude that mental images containing visual details that are irrelevant to an inference can even impede the process of reasoning. Persons who are blind from birth—and who thus do not tend to construct visual mental images—are immune to this visual-impedance effect.     

Animacy,perceptual load,and inattentional blindness

Inattentional blindness is the failure to notice unexpected objects in a visual scene while engaging in an attention-demanding task. We examined the effects of animacy and perceptual load on inattentional blindness. Participants searched for a category exemplar under low or high perceptual load. On the last trial, the participants were exposed to an unexpected object that was either animate or inanimate. Unexpected objects were detected more frequently when they were animate rather than inanimate, and more frequently with low than with high perceptual loads. We also measured working memory capacity and found that it predicted the detection of unexpected objects, but only with high perceptual loads. The results are consistent with the animate-monitoring hypothesis, which suggests that animate objects capture attention because of the importance of the detection of animate objects in ancestral hunter–gatherer environments.     

Relativism, sceptical paradox, and semantic blindness

Relativism about knowledge attributions is the view that a single occurrence of ‘S knows [does not know] that p’ may be true as assessed in one context and false as assessed in another context. It has been argued that relativism is equipped to accommodate all the data from speakers’ use of ‘know’ without recourse to an error theory. This is supposed to be relativism’s main advantage over contextualist and invariantist views. This paper argues that relativism does require the attribution of semantic blindness to speakers, viz. to account for sceptical paradoxes and epistemic closure puzzles. To that end, the notion of semantic blindness is clarified by distinguishing between content-blindness and index-blindness, and it is argued that the attribution of index-blindness required by the relativist account is implausible. Along the way, it is shown that error-theoretic objections from speakers’ inter-contextual judgments fail against relativism.     

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.