Journal of Abnormal Psychology 1992, Vol. 101, No. 1,192-199
Copyright 1992 by the American Psychological Association, Inc. 0021-843X/92/S3.00
Hypnosis, Reporting Bias, and Suggested Negative Hallucinations Nicholas P. Spanos, Cheryl A. Burgess, Patricia A. Cross, and Geoffrey MacLeod
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Carleton University, Ottawa, Ontario, Canada
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.
For more than a century, hypnosis has been associated with reports of dramatic, suggestion-induced changes in memory and perception. In most cases, however, the only available indexes of suggestion-induced experiential change have been either verbal report or other behaviors under subjects' direct voluntary control. Some researchers have used indirect indexes of perceptual and memory change. For example, response to delayed auditory feedback has been used to index hypnotic deafness (e.g., Sutcliffe, 1961). The results of these studies have typically indicated no evidence for perceptual or memory change on the indirect indexes despite subjects' reports of experiencing suggested changes. One interpretation of such findings is that hypnotic suggestions rarely if ever produce actual changes in perception or memory, but instead induce subjects to compliantly bias their reports in line with suggested demands (Sutcliffe, 1961; Wagstaff, 1981,1986). Compliant responding is biased responding, and it may be said to occur when subjects report experiences that they did not have or exaggerate experiences that they did have, in terms of situational demands (Orne & Scheibe, 1964; Wagstaff, 1981). Response biases of this kind may reflect either demand-induced lying or demand-induced retrospective reinterpretation of experience. In either case, demand-induced response biases reflect misdescriptions motivated by the desire to meet role expectations (Spanos, 1991; Wagstaff, 1981). Although the compliance hypothesis is an old one, it has failed to gain general acceptance for at least two reasons. First, a number of investigators have suggested that indirect indexes of perceptual and memory functioning do not validly reflect subjects' experiences. According to this hypothesis, for example, subjects might show at least partial hearing reduction in
response to deafness suggestions despite behaving in a "nondeaf" manner during delayed auditory feedback (Jones & Flynn, 1989). A second and more fundamental difficulty with the compliance hypothesis stems from the lack of a methodology with which to assess reporting bias independently of perceptual experience. For instance, reports of reduced pain or hearing after suggestion may to some extent reflect both actual perceptual change and demand-induced reporting bias. In the absence of some means for separating biased responding from perceptual change, investigators have been free to accept or reject suggestion-induced biased responding as a hypothesis on the basis of personal preference rather than data. Recently, we developed a paradigm that enabled suggestioninduced reporting bias to be assessed directly and independently of experiential changes during hypnotic deafness (Spanos, Burgess, & Perlini, in press) and hypnotic analgesia (Spanos, Perlini, Patrick, Bell & Gwynn, 1990). For instance, with respect to hypnotic deafness, the paradigm involved administering an easily audible tone on three successive trials. A 10-s waiting period followed termination of the tone on each trial, and after the waiting period subjects rated the loudness of the preceding tone. The first trial was a baseline, and the second was preceded by a hypnotic suggestion for deafness. After the second trial, the hypnotic suggestion was canceled and subjects were administered the third tone. After termination of Tone 3, but before subjects made their loudness ratings, different procedures were followed for experimental and control subjects. Control subjects simply waited 10 s and then rated the loudness of Tone 3, as they did on previous trials. In contrast, during the waiting period between the termination of the Tone 3 and the loudness rating, experimental subjects were informed that they had probably slipped into hypnosis and heard the last tone less loudly than they heard the baseline tone. This instruction was designed to produce reduction in the rated loudness of Tone 3 independent of subjects' actual perceptual experience of Tone 3.
This research was supported by a grant from the Natural Sciences and Engineering Research Council of Canada. Correspondence concerning this article should be addressed to Nicholas P. Spanos, Department of Psychology, Carleton University, Ottawa, Ontario K1S 5B6, Canada. 192
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HYPNOSIS, COMPLIANCE AND HALLUCINATION It is important to keep in mind that up to the termination of Tone 3, control subjects and experimental subjects were administered identical procedures and, therefore, presumably experienced equivalent levels of loudness during presentation of Tone 3. Consequently, any reduction in the rated loudness of this tone by experimental subjects relative to controls must reflect a reporting bias rather than a difference in perceptual experience. Control subjects tested in this paradigm reported no significant differences in the loudness of Tones 1 and 3. Therefore, for experimental subjects, reduction in Tone 3 loudness ratings relative to Tone 1 loudness ratings served as an index of the degree to which the demand instruction led subjects to bias their Tone 3 loudness reports. To investigate hypnotic analgesia, we (Spanos, Perlini, et al., 1990) replaced the tone with a pain stimulus and replaced the suggestion for deafness with a suggestion for pain reduction. Thus the two studies (Spanos et al., in press; Spanos et al., 1990) in which we have employed this paradigm have yielded the following findings. Subjects administered the demand instruction exhibited significant levels of reporting bias relative to controls. In fact, the degree of Trial 3 reporting bias was usually about half as large as the ratings of deafness and analgesia given after the hypnotic suggestion on Trial 2. It is important to note that the degree of Trial 3 reporting bias correlated strongly with Trial 2 ratings of deafness and analgesia. In other words, people who reported high levels of hypnotic deafness or analgesia on Trial 2 tended to be the same people who exhibited large reporting biases on Trial 3. In our paradigm, response to the Trial 3 demand instruction correlated with hypnotizability to the same extent that hypnotizability correlated with Trial 2 ratings of deafness and analgesia. Furthermore, when level of Trial 3 reporting bias was statistically controlled, the correlations between hypnotizability and deafness scores and hypnotizability and analgesia scores were much reduced and sometimes no longer statistically significant. In short, these findings suggest that demand-induced reporting bias plays an integral role in hypnotic responding and that much of the reporting change that follows hypnotic suggestions appears to be explicable in terms of reporting bias rather than in terms of actual changes in subjective experience. The present study included two experiments aimed at extending the findings thus far obtained with this paradigm. Experiment 1 was concerned with both the internal validity of the paradigm and the influence of reporting bias on open-ended subjective reports as well as on perceptual ratings. In Experiment 2 we assessed response to suggestions for negative visual hallucination as well as for deafness, and examined the role of strategy use and reporting bias at influencing reports of negative visual hallucination.
Experiment 1 In our earlier study on hypnotic deafness and reporting bias (Spanos et al., in press), both experimental and control subjects were administered a hypnotic deafness suggestion before Tone 2, but received no instructions before Tone 3. As already described, controls returned to baseline levels of reported loudness on Tone 3, whereas those administered the demand instruction reported less loudness than they had on baseline, but
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more loudness than they had on the hypnotic deafness trial (Tone 2). The increase in loudness reported by these subjects from Trial 2 to Trial 3 is open to several interpretations. One possibility is that subjects would have reported an increase in loudness across these trials even if they had been administered a hypnotic deafness suggestion before each trial. Alternatively, the higher loudness reported after the demand instruction (Tone 3) than after the suggestion (Tone 2) may indicate that the demand manipulation was less potent than hypnotic suggestion at lowering loudness ratings. One purpose of the present study was to assess these alternative hypotheses by testing three groups of highly hypnotizable subjects on three tone trials. Subjects in Groups 1 and 2 were administered, respectively, the control sequence and the demand instruction sequence described earlier. Those in Group 3 were also administered a Trial 1 baseline tone and a hypnotic deafness suggestion before Tone 2. However, instead of canceling the hypnosis and suggestion after Trial 2, we gave these subjects another deafness suggestion before Trial 3. This design enabled us to determine whether the increase in rated loudness that occurs from Trial 2 (deafness suggestion) to Trial 3 (demand instruction) reflects differences in the potency of the suggestion and instruction manipulations or is a result of repeated exposure to the tone after either suggestion or demand instruction. Hypnotic suggestions for perceptual change often explicitly instruct subjects to use cognitive strategies to bring about the requisite experiences. Furthermore, subjects who report the perceptual experiences called for often report using the strategies contained in the suggestion or other strategies of their own making (e.g., Spanos, Radtke-Bodorik, Ferguson, & Jones, 1979). After Trial 3 all subjects in the present experiment completed four increasingly explicit questionnaires that asked them to describe their experiences on Trial 3. This procedure allowed us to determine whether subjects given the demand instruction would bias their postexperimental reports by reporting the use of cognitive strategies and whether any such biasing effects were a function of the amount of information supplied to subjects by the questionnaires that purported to assess their experience.
Method Subjects. Forty-five Carleton University undergraduates volunteered to participate in a one-session study on suggestion and auditory perception. These subjects had previously been scored as highly hypnotizable (scores of 5-7) on the objective dimension of the Carleton University Responsiveness to Suggestion Scale (CURSSrO; Spanos, Radtke, Hodgins, Stam, & Bertrand, 1983). All subjects received course credit for their participation. Apparatus and materials. Three identical repetitions of a 30-s, 60dB, 1000-Hz pure tone were prerecorded on a BASF magnetic tape and presented to subjects over Sony DR-27 headphones from a Philips D8270 tape recorder. Half the subjects received the tone in the left ear, and half received it in the right ear. On each trial, 10 s after termination of the tone, subjects verbally rated its loudness using a 21-point category rating scale. This scale contained alternatives ranging from no sound (Q) to intensely loud (20). Procedure. All subjects were individually tested by the same female experimenter. Subjects were randomly assigned to one of three condi-
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tions, with the restriction that there be an equal number of subjects (n = 15) in each condition. Before their baseline trial, subjects were instructed to give their loudness ratings after the termination of the tone, when the experimenter tapped the back of their hands (10s after stimulus termination). Subjects were requested to close their eyes and were presented with the baseline auditory test trial. After the baseline loudness reports, a 10-min hypnotic induction procedure (adapted from Barber, 1969) was administered to all 45 subjects. This was followed by a suggestion for deafness that informed subjects that hypnosis would enable them to use their imaginal and attentional processes to control sensory input and that on the next trial they were to use these abilities to reduce the loudness of the tone. After providing their Trial 2 loudness ratings, subjects were administered their respective treatments. Fifteen subjects (the hypnosis group) were given a reinforced hypnotic deafness suggestion that informed them that they were to continue to relax and drift deeper into hypnosis. This was followed by the same deafness suggestion administered on Trial 2. After their Trial 3 loudness reports, these subjects were awakened and the deafness suggestion was canceled. After making their Trial 2 ratings, the remaining subjects (n = 30) were administered a wake-up procedure and cancellation of the deafness suggestion. For these subjects, Trial 3 was preceded with the instruction that this last trial would be "just like Trial 1." In the 10 s after termination of the Trial 3 tone, but before making their loudness ratings, half of these subjects (n = 15) received the following demand instruction: People who are exposed to the tone more than once tend to drift back into hypnosis, and this greatly reduces the intensity of the sound that they hear. You probably drifted into hypnosis on this last trial, and for this reason, heard very little of the tone. The other half (the control group) were not given any instruction before making their final loudness ratings. At the end of the third trial (after their loudness ratings), subjects in all conditions were given three open-ended questionnaires designed to assess their reported subjective experience of the Trial 3 tone. On the first questionnaire subjects described everything they had experienced on the last trial (Trial 3). On the second questionnaire subjects provided more details about what they had experienced on the last trial. On the third they reported what, if anything, they had done on the last trial in order to hear the tone less loudly. Subjects who reported using a strategy on the first questionnaire received a score of 3, those who first reported strategy use on the second questionnaire were scored 2, and those who first reported strategy use on the third questionnaire were scored 1. Subjects who failed to report strategy use on any of the questionnaires were scored 0. Two independent judges who were unaware of subjects' treatment assignment agreed on their strategy score 89% of the time. After completing these open-ended questionnaires, subjects were administered a 9-point Likert-type scale on which they rated the extent to which they had used imaginal or distraction techniques in order to reduce the loudness of the Trial 3 tone. The scale alternatives ranged from not at all (1) to all the time (9).
Results Reductions in reported loudness. A 3 X 3 (Group [hypnosis, demand, or control] X Trial [1,2, or 3]) mixed analysis of variance (ANOYA) performed on the loudness ratings yielded a significant Group X Trial interaction, F(4,84) = 15.84, p < .001. This interaction was analyzed further in terms of simple main effects, and the relevant means are shown in Table 1. The simple
main effects for group at Trials 1 and 2 failed to approach significance. In other words, subjects in the three groups reported equivalent levels of loudness on both the baseline trial and Trial 2. Within-group simple effects analyses revealed that subjects given the reinforced hypnotic deafness suggestion, F(2, 84) = 33.58, p < .001, subjects given the demand instruction, F(2, 84) = 35.64, p < .001, and the control subjects, F(2,84) = 35.53, p < .001, reported significant changes in the loudness of the tone across the three trials. Post hoc comparisons indicated that subjects given the reinforced hypnotic deafness suggestion reported the tone as significantly less loud on Trials 2 and 3 than on the baseline trial. The latter two means failed to differ significantly. Subjects administered the demand instruction also reported significantly lower loudness on Trial 2 (suggested deafness) and on Trial 3 (demand instruction) than on the baseline trial. However, the Trial 3 loudness ratings of these subjects were slightly but significantly higher than their Trial 2 loudness ratings. For the control subjects, Trial 2 loudness reports were substantially lower than those of either the baseline trial or Trial 3. Furthermore, the Trial 3 ratings of these subjects did not differ significantly from their baseline ratings. In summary, all subjects reported equivalent and substantial hearing loss in response to the deafness suggestion on Trial 2. However, subjects in the three conditions exhibited different patterns of response from Trial 2 to Trial 3. Subjects who received hypnotic deafness suggestions on both Trials 2 and 3 reported equivalent hearing loss on these two trials. Subjects given the demand instruction also reported significant Trial 3 loudness reduction, but to a less degree than that exhibited on Trial 2. In contrast, Trial 3 loudness reports for the control subjects did not differ from their baseline trial reports. Reported deafness and cognitive strategies. A one-way ANOVA performed on the cognitive strategy scores obtained from the open-ended questionnaires was significant, F(2,42) = 5.22, p < .01. Subjects who received the reinforced hypnotic deafness suggestion on Trial 3 attained significantly higher cognitive strategy scores (M = 2.20, SD = .94) than did subjects given the demand instruction (M = 1.47, SD = 1.06) and the control subjects (M = 1.00, SD = 1.07). Those in the latter two groups did not differ significantly in cognitive strategy scores. A one-way ANOVA performed on subjects' scale ratings of strategy use was significant, F(2, 42) = 6.84, p < .01. Post hoc comparisons revealed that both the reinforced hypnosis subjects (M = 6.53, SD =1.51) and the demand instruction subjects (M = 6.60, SD = 1.24) rated themselves as using cognitive strategies to a greater extent than did the control subjects (M = 4.60, SD = 2.16). The strategy use ratings of demand instruction Table 1 Mean Loudness Ratings by Group Trial 1
Trial 2
Trial3
Group
M
SD
M
SD
M
SD
Hypnosis Demand Instruction Control
14.27 13.47 14.93
3.49 4.02 3.13
10.40 8.07 10.80
4.66 2.71 3.99
9.27 10.87 15.87
5.02 4.57 3.78
HYPNOSIS, COMPLIANCE AND HALLUCINATION subjects failed to differ significantly from the ratings of subjects in the hypnosis condition.
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Discussion Our findings replicate those of earlier studies (Spanos et al, in press; Spanos et al., 1990) and provide strong support for the hypothesis that reports of suggestion-induced perceptual alteration proffered by highly hypnotizable hypnotic subjects reflect, to a substantial degree, reporting biases rather than actual changes in perceptual processing. In addition, the present findings indicate that the increase in loudness reported from Trial 2 (hypnotic deafness) to Trial 3 (demand instruction) by subjects given the demand manipulation cannot be explained in terms of repeated exposure to the tone. Subjects who were given the hypnotic suggestion before Trial 2 and again before Trial 3 continued to report the same low levels of loudness on both trials. These findings indicate that hypnotic suggestions were slightly but significantly more potent at inducing reports of deafness than was the demand instruction employed in this research. These findings might mean that Trial 2 loudness reduction scores reflect a small perceptual alteration component that was added to a reporting bias component. Alternatively, these findings might simply mean that hypnotic suggestions contained stronger demands to bias perceptual reports than did our demand instruction. Regardless of which hypothesis eventually proves true, the present findings clearly support Wagstaff's (1981,1986) contention that suggestion-induced reporting bias is a central component in hypnotic responding. Subjects given the deafness suggestion before Trial 3 reported more use of cognitive strategies in their open-ended reports than did either control subjects or subjects given the demand instruction. As already mentioned, only subjects given the Trial 3 suggestion maintained equivalent levels of reported loudness reduction across Trials 2 and 3. One interpretation of these findings is that strategy use led to the greater-than-demand loudness reductions in subjects given the Trial 3 suggestion. On the other hand, these findings could indicate that subjects who received the Trial 3 suggestion were particularly likely to indicate strategy use because only these subjects had been given a suggestion that explicitly instructed them to use strategies on Trial 3. The open-ended questionnaires, by themselves, contained few cues that strategy reporting was required. Consequently, most subjects given the demand instruction may have been unaware that such reporting was called for. However, when these subjects were given the final Likert-type scale that explicitly asked them to rate the extent of their strategy use, their ratings on this dimension were as high as those of the subjects given the Trial 3 deafness suggestion. In other words, subjects were quite willing to bias their reports of strategy use as well as their loudness reports. However, such biasing was unlikely to occur in the demand instruction condition until these subjects were provided (via an explicit questionnaire) with the requisite information about the responses called for. Such information was provided by the suggestion for those subjects who received a suggestion before Trial 3. Consequently, for subjects in this condition, open-ended reports of strategy use and the relationship between such reports and reported loudness reductions remain ambiguous. It would be of interest in a future
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study to administer deafness suggestions that did not provide cognitive strategies. If subjects who received these suggestions continued to report greater strategy use on open-ended questionnaires and greater loudness reductions on Trial 3 than subjects given a demand instruction, support would be provided for the hypothesis that strategy use produces effects on perceptual reports above and beyond the effects of reporting bias.
Experiment 2 Negative visual hallucinations are suggestion-induced reports of an inability to see a target stimulus. Negative visual hallucination suggestions are among the most difficult items on standardized hypnotizability scales (Hilgard, 1965) and are usually "passed" by only highly hypnotizable subjects. Although relatively little empirical work has focused on negative visual hallucinations, some evidence indicates that reporting bias may play a prominent role in this phenomenon. Spanos, Flynn, and Gabora (1989) gave highly hypnotizable subjects the suggestion that, on opening their eyes, they would see only a blank piece of paper. In fact, the number 8 was displayed prominently on the paper. Subjects who reported seeing nothing on the paper were interviewed by a second experimenter, who implied to them that seeing nothing was the response typically given only by fakers, whereas seeing a figure that gradually faded over 1 min was typical of truly hypnotized people. Subjects were then given the opportunity to draw what they had seen on the paper at successive points after they had opened their eyes. Under these circumstances, 14 out of 15 subjects who had initially insisted that they saw nothing on the paper now drew a number 8 as the figure seen when they first opened their eyes. In other words, when demands to report having "seen nothing" were lifted, almost all of these highly hypnotizable subjects acknowledged through their drawings that they had seen the target figure they had earlier denied seeing. These findings do not mean that subjects in the Spanos et al. (1989) experiment failed to experience any perceptual distortion after the suggestion. By employing simple ocular strategies such as unfocusing the eyes, or averting gaze from the target stimulus, subjects can easily produce blurring and other distortions of visual perception. Subjects in the Spanos et al. experiment and in other experiments on negative hallucination may well have employed such strategies to induce perceptual distortions. Nevertheless, Spanos et al.'s findings suggest that, regardless of any such distortions in perception, subjects clearly exaggerated their experiences in line with suggested demands by stating that they could see nothing on the paper. Although hypnotic subjects are exposed to explicit demands to gear their reports in line with the requests of suggestions, they are also exposed to implicit demands to report honestly and accurately about their experiences (deGroot & Gwynn, 1989; Spanos, 1986). Furthermore, hypnotic subjects are likely to differ substantially in the extent to which they are sensitive to norms for honest reporting. Consequently, such subjects are likely to exaggerate and distort their experiences to different degrees in response to experimental demands. Although the Spanos et al. (1989) study indicated that negative hallucinators exaggerate their experiences in terms of sug-
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gested demands, it provided no means of assessing individual differences in the degree of such reporting bias. Moreover, neither Spanos et al. nor other researchers have assessed the cognitive strategies that subjects employ in order to distort their perceptual experiences and define themselves as "not seeing." In Experiment 2, we assessed the strategies for "not seeing" that subjects reported in response to a negative visual hallucination suggestion and examined the relationship between the use of such strategies and the degree to which subjects reported blindness. In addition, the role of reporting bias in negative visual hallucination responding was assessed by testing subjects in the deafness paradigm described in Experiment 1 and examining the relationship between bias scores obtained in that paradigm and blindness scores obtained in response to a negative visual hallucination suggestion. We anticipated that reporting bias in the deafness paradigm would correlate significantly with reports of blindness after the suggestion for negative visual hallucination. Method Subjects. Forty-nine Carleton University undergraduates volunteered to participate in a study of perception and hypnosis. These subjects had previously tested as either medium (scores of 3 or 4) or high (scores of 5-7) on the CURS&O (Spanos et al., 1983). All subjects received course credit for their participation. Procedure. All subjects were tested individually by the same male experimenter in two sessions. In the first session subjects were asked to close their eyes and were administered the 10-min hypnotic induction procedure used in Experiment 1. This was followed by a suggestion for blindness that informed subjects that they were to become actively involved in the suggestion and were to use whatever strategies they could to make a word disappear from a piece of paper. Subjects were then instructed to look at an 8.5 in. X 11 in. sheet of white paper that was held approximately 50 cm in front of their eyes. On the paper was printed the word DINOSAUR in letters 20 mm in height. The suggestion instructed subjects to notice that the word was fading more and more, until it completely disappeared and the paper was blank. They were then asked to describe what they saw on the paper. Following Bryant and McConkey (1989), subjects who reported seeing all or part of the word DINOSAUR were given a prompt that encouraged them to try harder and to use whatever strategies they could to make the word fade and disappear. After the prompt, these subjects were again asked what they saw on the paper. After their verbal reports, a wake-up procedure was administered and the blindness suggestion was canceled. Blindness scores were computed as follows. Subjects who in their initial descriptions reported seeing nothing on the paper were given a blindness score of 2. Subjects who initially reported seeing all or part of the word but reported complete blindness after the prompt received a score of 1. Finally, subjects who failed to report blindness despite the prompt received a score of 0. Subjects were next administered a 5-point scale asking them to rate the extent of their blindness. Scale alternatives ranged from not at all (0) to completely (4). After completion of this hypnotic blindness selfrating, subjects wrote responses to a one-page, open-ended questionnaire that asked them what, if anything, they had done in order to "not see" the word. This questionnaire was scored for cognitive strategy use by two independent judges who were unaware of subjects' experimental condition and level of hypnotizability. Judges scored each subject as reporting strategy use (1) or not reporting strategy use (0). Judges agreed 92% of the time, and discrepancies were resolved through discussion. Finally, the subjects were given a list of seven possible strategies and
were asked to circle as many as they had used in their attempt to make the word disappear. These strategies were listed as follows: 1. I unfocused my eyes. 2. I crossed my eyes. 3. I looked above, below, or away from the word, rather than looking right at it. 4. I created a visual image to cover or block the word. 5. I tried to imagine a different word. 6. I tried to think of other things, so as not to notice the word. 7. Other (specify). Subjects were tested in a second individual session within 2 weeks of the first. During the second session, 34 subjects were administered the deafness paradigm with the demand instruction after Tone 3 in the same manner as in Experiment 1. The remaining 15 subjects were administered the control sequence of the paradigm. After their loudness ratings all subjects were administered two open-ended questionnaires taken from Experiment 1 (Questionnaires 1 and 3) that assessed reported strategy use during the Trial 3 tone. Subjects were scored 2 if they reported strategy use on the first questionnaire, 1 if they reported strategy use on the second questionnaire, and 0 if they failed to report strategy use on either questionnaire. Two independent judges agreed on these ratings 92% of the time. Results Compliance and control. A Hotelling's T2 analysis that compared the scores of Session 2 experimental and control subjects on the CURSS dimensions, open-ended blindness reports, blindness scale self-ratings, and judges' blindness strategy use ratings failed to approach significance. Thus subjects in the demand instruction and control conditions were equivalent on these measures. Session 2 experimental effects. A 2 X 3 (Condition [demand instruction or control] X Trial [1, 2, or 3]) mixed ANOV\ on loudness ratings yielded a significant interaction, F(2, 94) = 3.88, p < .025, that was analyzed further in terms of simple main effects. As shown in Table 2, the simple main effects for condition at Trials 1 and 2 failed to approach significance, indicating that subjects in the demand instruction and control conditions of Session 2 reported equivalent levels of loudness on these two trials. However, a significant simple main effect was found for condition at Trial 3, F(l, 70) = 6.28, p < .025. Subjects who received the demand instruction reported significantly lower Trial 3 loudness ratings than did the nondemand (control) subjects. Analyses within conditions revealed that significant changes in the loudness of the tone across trials were reported by subjects given the demand instruction, F(2,94) = 30.14, p< .001, and also by subjects not given the demand instruction (con-
Table 2 Mean Loudness Ratings for Demand Instruction and Control Subjects Trial 1
Trial 2
Trial 3
Subjects
M
SD
M
SD
M
SD
Demand Instruction Control
13.29 14.20
3.94 3.65
9.47 10.20
3.32 4.02
11.44 14.40
3.82 4.42
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HYPNOSIS, COMPLIANCE AND HALLUCINATION trols), F(2, 94) = 20.42, p < .001. Post hoc comparisons (least significant difference) indicated that subjects given the demand instruction reported significant loudness reductions on Trial 2 (suggested deafness) and on Trial 3 (demand instruction). However, Trial 3 reported loudness reductions were significantly smaller than those of Trial 2. The nondemand subjects reported significantly lower loudness on Trial 2 than on Trial 1 or 3. Loudness ratings on Trials 1 and 3 failed to differ significantly. Reporting bias in "blind" and"not blind"subjects. Analyses of relationships between Session 2 reporting bias and response to the Session 1 negative visual hallucination suggestion included only those subjects who were administered the demand instruction in Session 2. For each of these subjects, a Session 2 reporting bias score was obtained by subtracting their Trial 3 (demand instruction) loudness score from their Trial 1 score. We anticipated that subjects who reported complete blindness in Session 1 would report greater Session 2 reporting bias then subjects who reported little or no blindness in Session 1. This hypothesis was tested in an analysis that included only those subjects who rated themselves as exhibiting complete blindness (self-rating of 4, n = 11) or little or no blindness (selfrating of 1 or 0,« = 9) in Session 1. As predicted, subjects who reported complete blindness (M = 3.73, SD = 2.65) exhibited substantially and significantly greater Session 2 reporting bias than those who did not report blindness (M= .33, SD = 3.24), /(18) = 2.58 p < .05. Strategies for blindness and deafness. On the basis of their Session 1 open-ended reports, 40 subjects (82%) were rated as using one or more strategies in an attempt to "not see" the target word. However, in response to the seven-item list of strategies, all subjects reported using at least one strategy. The percentages of subjects who chose each listed strategy are given in Table 3. Twelve subjects (24%) chose Strategy 7 on the strategy checklist, indicating that they had used strategies other than the available choices. Closer examination revealed that 8 of these subjects (67%) reported ocular fixation on only a limited aspect of the stimulus (i.e., staring fixedly at a letter or portion of the word DINOSAUR); 2 subjects (17%) described sensations experienced during the suggestion, such as a blurriness of vision, rather than reporting a specific strategy; 1 subject reiterated that he had visualized a piece of white paper covering the
Table 3 Number and Percentage of Subjects Who Reported Using Each Strategy Strategy
1.
2. 3. 4. 5. 6. 7.
I unfocused my eyes. I crossed my eyes. I looked above, below, or away from the word, rather than looking right at it. I created a visual image to cover or block the word. I tried to imagine a different word. I tried to think of other things, so as not to notice the word. Other (specify).
No. of subjects
%
33 7
67 14
29
59
13 4
27 8
6 12
12 24
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word (Strategy 4); and the remaining subject simply reported "I blanked my mind." A t test comparing Session 2 demand instruction and control subjects on auditory strategy scores obtained from the openended questionnaires failed to approach significance. As in Experiment 1, subjects who received the demand instruction (M= .74, SD = .57) reported no greater use of cognitive strategies to reduce the loudness of the Trial 3 tone than did control subjects Correlations. Table 4 shows the correlations among the dependent variables assessed in Sessions 1 and 2 for subjects given the demand instruction in Session 2. Difference scores were used to compute Session 2 deafness scores (baseline-Trial 2) and reporting bias scores (baseline-Trial 3). In Session 2, the correlation between Trial 2 deafness scores and Trial 3 reporting bias scores was substantial and indicated that to a large extent subjects who reported high levels of hypnotic deafness were the same persons who, on the next trial, biased their reports in terms of experimental demands. Interestingly, the extent to which subjects biased their reports on Trial 3 also correlated significantly with the extent to which they reported use of cognitive strategies on that trial. In other words, subjects who biased their reports of hearing reduction to a relatively large degree also tended to be attuned enough to experimental demands to generate reports of strategy use on the basis of the minimal cues provided by the open-ended questionnaires. In Session 1, the correlation between open-ended reports of blindness and self-ratings of blindness was very high and supports the notion that these two indexes assessed the same response dimension. Neither of these Session 1 blindness indexes correlated significantly with the extent of strategy use reported by subjects in response to the negative visual hallucination suggestion. On the other hand, both Session 1 blindness indexes correlated significantly with Session 2 deafness ratings and reporting bias scores. More important, the partial correlations between deafness ratings and open-ended reports of blindness, r(31) = .03, and between deafness ratings and self-ratings of blindness, r(31) = .22, were not significant when the effects of reporting bias scores were statistically controlled. Reporting bias scores, like blindness scores, did not correlate significantly with the extent of subjects' strategy use in response to the Session 1 suggestion. Taken together, these findings indicate that reporting bias influenced response to suggestions for negative visual hallucination as well as response to deafness suggestions. Moreover, the correlation between reports of suggested blindness and deafness was mediated by subjects' tendency to bias their perceptual reports in terms of suggested demands.
General Discussion The findings of Experiment 2 concerning suggested deafness replicate those of Experiment 1 as well as those of Spanos et al. (in press) and indicate that demand-induced reporting bias plays an important role in the phenomenon of hypnotic deafness. The results of Experiments 1 and 2 further indicate that compliance pressures lead subjects to bias their reports of auditory strategy use as well as their reports of reduced hearing. When assessment procedures explicitly implied that the report-
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Table 4 Correlations Among Session 1 and Session 2 Dependent Variables in Experiment 2 Variable 1. 2. 3. 4. 5. 6.
Suggested deafness Reporting bias Deafness strategies Judges' blindness ratings Self-ratings of blindness Blindness strategies
1
.79**
.39* .35*
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Copyright 1992 by the American Psychological Association, Inc. 0021-843X/92/S3.00
Hypnosis, Reporting Bias, and Suggested Negative Hallucinations Nicholas P. Spanos, Cheryl A. Burgess, Patricia A. Cross, and Geoffrey MacLeod
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Carleton University, Ottawa, Ontario, Canada
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.
For more than a century, hypnosis has been associated with reports of dramatic, suggestion-induced changes in memory and perception. In most cases, however, the only available indexes of suggestion-induced experiential change have been either verbal report or other behaviors under subjects' direct voluntary control. Some researchers have used indirect indexes of perceptual and memory change. For example, response to delayed auditory feedback has been used to index hypnotic deafness (e.g., Sutcliffe, 1961). The results of these studies have typically indicated no evidence for perceptual or memory change on the indirect indexes despite subjects' reports of experiencing suggested changes. One interpretation of such findings is that hypnotic suggestions rarely if ever produce actual changes in perception or memory, but instead induce subjects to compliantly bias their reports in line with suggested demands (Sutcliffe, 1961; Wagstaff, 1981,1986). Compliant responding is biased responding, and it may be said to occur when subjects report experiences that they did not have or exaggerate experiences that they did have, in terms of situational demands (Orne & Scheibe, 1964; Wagstaff, 1981). Response biases of this kind may reflect either demand-induced lying or demand-induced retrospective reinterpretation of experience. In either case, demand-induced response biases reflect misdescriptions motivated by the desire to meet role expectations (Spanos, 1991; Wagstaff, 1981). Although the compliance hypothesis is an old one, it has failed to gain general acceptance for at least two reasons. First, a number of investigators have suggested that indirect indexes of perceptual and memory functioning do not validly reflect subjects' experiences. According to this hypothesis, for example, subjects might show at least partial hearing reduction in
response to deafness suggestions despite behaving in a "nondeaf" manner during delayed auditory feedback (Jones & Flynn, 1989). A second and more fundamental difficulty with the compliance hypothesis stems from the lack of a methodology with which to assess reporting bias independently of perceptual experience. For instance, reports of reduced pain or hearing after suggestion may to some extent reflect both actual perceptual change and demand-induced reporting bias. In the absence of some means for separating biased responding from perceptual change, investigators have been free to accept or reject suggestion-induced biased responding as a hypothesis on the basis of personal preference rather than data. Recently, we developed a paradigm that enabled suggestioninduced reporting bias to be assessed directly and independently of experiential changes during hypnotic deafness (Spanos, Burgess, & Perlini, in press) and hypnotic analgesia (Spanos, Perlini, Patrick, Bell & Gwynn, 1990). For instance, with respect to hypnotic deafness, the paradigm involved administering an easily audible tone on three successive trials. A 10-s waiting period followed termination of the tone on each trial, and after the waiting period subjects rated the loudness of the preceding tone. The first trial was a baseline, and the second was preceded by a hypnotic suggestion for deafness. After the second trial, the hypnotic suggestion was canceled and subjects were administered the third tone. After termination of Tone 3, but before subjects made their loudness ratings, different procedures were followed for experimental and control subjects. Control subjects simply waited 10 s and then rated the loudness of Tone 3, as they did on previous trials. In contrast, during the waiting period between the termination of the Tone 3 and the loudness rating, experimental subjects were informed that they had probably slipped into hypnosis and heard the last tone less loudly than they heard the baseline tone. This instruction was designed to produce reduction in the rated loudness of Tone 3 independent of subjects' actual perceptual experience of Tone 3.
This research was supported by a grant from the Natural Sciences and Engineering Research Council of Canada. Correspondence concerning this article should be addressed to Nicholas P. Spanos, Department of Psychology, Carleton University, Ottawa, Ontario K1S 5B6, Canada. 192
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HYPNOSIS, COMPLIANCE AND HALLUCINATION It is important to keep in mind that up to the termination of Tone 3, control subjects and experimental subjects were administered identical procedures and, therefore, presumably experienced equivalent levels of loudness during presentation of Tone 3. Consequently, any reduction in the rated loudness of this tone by experimental subjects relative to controls must reflect a reporting bias rather than a difference in perceptual experience. Control subjects tested in this paradigm reported no significant differences in the loudness of Tones 1 and 3. Therefore, for experimental subjects, reduction in Tone 3 loudness ratings relative to Tone 1 loudness ratings served as an index of the degree to which the demand instruction led subjects to bias their Tone 3 loudness reports. To investigate hypnotic analgesia, we (Spanos, Perlini, et al., 1990) replaced the tone with a pain stimulus and replaced the suggestion for deafness with a suggestion for pain reduction. Thus the two studies (Spanos et al., in press; Spanos et al., 1990) in which we have employed this paradigm have yielded the following findings. Subjects administered the demand instruction exhibited significant levels of reporting bias relative to controls. In fact, the degree of Trial 3 reporting bias was usually about half as large as the ratings of deafness and analgesia given after the hypnotic suggestion on Trial 2. It is important to note that the degree of Trial 3 reporting bias correlated strongly with Trial 2 ratings of deafness and analgesia. In other words, people who reported high levels of hypnotic deafness or analgesia on Trial 2 tended to be the same people who exhibited large reporting biases on Trial 3. In our paradigm, response to the Trial 3 demand instruction correlated with hypnotizability to the same extent that hypnotizability correlated with Trial 2 ratings of deafness and analgesia. Furthermore, when level of Trial 3 reporting bias was statistically controlled, the correlations between hypnotizability and deafness scores and hypnotizability and analgesia scores were much reduced and sometimes no longer statistically significant. In short, these findings suggest that demand-induced reporting bias plays an integral role in hypnotic responding and that much of the reporting change that follows hypnotic suggestions appears to be explicable in terms of reporting bias rather than in terms of actual changes in subjective experience. The present study included two experiments aimed at extending the findings thus far obtained with this paradigm. Experiment 1 was concerned with both the internal validity of the paradigm and the influence of reporting bias on open-ended subjective reports as well as on perceptual ratings. In Experiment 2 we assessed response to suggestions for negative visual hallucination as well as for deafness, and examined the role of strategy use and reporting bias at influencing reports of negative visual hallucination.
Experiment 1 In our earlier study on hypnotic deafness and reporting bias (Spanos et al., in press), both experimental and control subjects were administered a hypnotic deafness suggestion before Tone 2, but received no instructions before Tone 3. As already described, controls returned to baseline levels of reported loudness on Tone 3, whereas those administered the demand instruction reported less loudness than they had on baseline, but
193
more loudness than they had on the hypnotic deafness trial (Tone 2). The increase in loudness reported by these subjects from Trial 2 to Trial 3 is open to several interpretations. One possibility is that subjects would have reported an increase in loudness across these trials even if they had been administered a hypnotic deafness suggestion before each trial. Alternatively, the higher loudness reported after the demand instruction (Tone 3) than after the suggestion (Tone 2) may indicate that the demand manipulation was less potent than hypnotic suggestion at lowering loudness ratings. One purpose of the present study was to assess these alternative hypotheses by testing three groups of highly hypnotizable subjects on three tone trials. Subjects in Groups 1 and 2 were administered, respectively, the control sequence and the demand instruction sequence described earlier. Those in Group 3 were also administered a Trial 1 baseline tone and a hypnotic deafness suggestion before Tone 2. However, instead of canceling the hypnosis and suggestion after Trial 2, we gave these subjects another deafness suggestion before Trial 3. This design enabled us to determine whether the increase in rated loudness that occurs from Trial 2 (deafness suggestion) to Trial 3 (demand instruction) reflects differences in the potency of the suggestion and instruction manipulations or is a result of repeated exposure to the tone after either suggestion or demand instruction. Hypnotic suggestions for perceptual change often explicitly instruct subjects to use cognitive strategies to bring about the requisite experiences. Furthermore, subjects who report the perceptual experiences called for often report using the strategies contained in the suggestion or other strategies of their own making (e.g., Spanos, Radtke-Bodorik, Ferguson, & Jones, 1979). After Trial 3 all subjects in the present experiment completed four increasingly explicit questionnaires that asked them to describe their experiences on Trial 3. This procedure allowed us to determine whether subjects given the demand instruction would bias their postexperimental reports by reporting the use of cognitive strategies and whether any such biasing effects were a function of the amount of information supplied to subjects by the questionnaires that purported to assess their experience.
Method Subjects. Forty-five Carleton University undergraduates volunteered to participate in a one-session study on suggestion and auditory perception. These subjects had previously been scored as highly hypnotizable (scores of 5-7) on the objective dimension of the Carleton University Responsiveness to Suggestion Scale (CURSSrO; Spanos, Radtke, Hodgins, Stam, & Bertrand, 1983). All subjects received course credit for their participation. Apparatus and materials. Three identical repetitions of a 30-s, 60dB, 1000-Hz pure tone were prerecorded on a BASF magnetic tape and presented to subjects over Sony DR-27 headphones from a Philips D8270 tape recorder. Half the subjects received the tone in the left ear, and half received it in the right ear. On each trial, 10 s after termination of the tone, subjects verbally rated its loudness using a 21-point category rating scale. This scale contained alternatives ranging from no sound (Q) to intensely loud (20). Procedure. All subjects were individually tested by the same female experimenter. Subjects were randomly assigned to one of three condi-
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SPANOS, BURGESS, CROSS, AND MACLEOD
tions, with the restriction that there be an equal number of subjects (n = 15) in each condition. Before their baseline trial, subjects were instructed to give their loudness ratings after the termination of the tone, when the experimenter tapped the back of their hands (10s after stimulus termination). Subjects were requested to close their eyes and were presented with the baseline auditory test trial. After the baseline loudness reports, a 10-min hypnotic induction procedure (adapted from Barber, 1969) was administered to all 45 subjects. This was followed by a suggestion for deafness that informed subjects that hypnosis would enable them to use their imaginal and attentional processes to control sensory input and that on the next trial they were to use these abilities to reduce the loudness of the tone. After providing their Trial 2 loudness ratings, subjects were administered their respective treatments. Fifteen subjects (the hypnosis group) were given a reinforced hypnotic deafness suggestion that informed them that they were to continue to relax and drift deeper into hypnosis. This was followed by the same deafness suggestion administered on Trial 2. After their Trial 3 loudness reports, these subjects were awakened and the deafness suggestion was canceled. After making their Trial 2 ratings, the remaining subjects (n = 30) were administered a wake-up procedure and cancellation of the deafness suggestion. For these subjects, Trial 3 was preceded with the instruction that this last trial would be "just like Trial 1." In the 10 s after termination of the Trial 3 tone, but before making their loudness ratings, half of these subjects (n = 15) received the following demand instruction: People who are exposed to the tone more than once tend to drift back into hypnosis, and this greatly reduces the intensity of the sound that they hear. You probably drifted into hypnosis on this last trial, and for this reason, heard very little of the tone. The other half (the control group) were not given any instruction before making their final loudness ratings. At the end of the third trial (after their loudness ratings), subjects in all conditions were given three open-ended questionnaires designed to assess their reported subjective experience of the Trial 3 tone. On the first questionnaire subjects described everything they had experienced on the last trial (Trial 3). On the second questionnaire subjects provided more details about what they had experienced on the last trial. On the third they reported what, if anything, they had done on the last trial in order to hear the tone less loudly. Subjects who reported using a strategy on the first questionnaire received a score of 3, those who first reported strategy use on the second questionnaire were scored 2, and those who first reported strategy use on the third questionnaire were scored 1. Subjects who failed to report strategy use on any of the questionnaires were scored 0. Two independent judges who were unaware of subjects' treatment assignment agreed on their strategy score 89% of the time. After completing these open-ended questionnaires, subjects were administered a 9-point Likert-type scale on which they rated the extent to which they had used imaginal or distraction techniques in order to reduce the loudness of the Trial 3 tone. The scale alternatives ranged from not at all (1) to all the time (9).
Results Reductions in reported loudness. A 3 X 3 (Group [hypnosis, demand, or control] X Trial [1,2, or 3]) mixed analysis of variance (ANOYA) performed on the loudness ratings yielded a significant Group X Trial interaction, F(4,84) = 15.84, p < .001. This interaction was analyzed further in terms of simple main effects, and the relevant means are shown in Table 1. The simple
main effects for group at Trials 1 and 2 failed to approach significance. In other words, subjects in the three groups reported equivalent levels of loudness on both the baseline trial and Trial 2. Within-group simple effects analyses revealed that subjects given the reinforced hypnotic deafness suggestion, F(2, 84) = 33.58, p < .001, subjects given the demand instruction, F(2, 84) = 35.64, p < .001, and the control subjects, F(2,84) = 35.53, p < .001, reported significant changes in the loudness of the tone across the three trials. Post hoc comparisons indicated that subjects given the reinforced hypnotic deafness suggestion reported the tone as significantly less loud on Trials 2 and 3 than on the baseline trial. The latter two means failed to differ significantly. Subjects administered the demand instruction also reported significantly lower loudness on Trial 2 (suggested deafness) and on Trial 3 (demand instruction) than on the baseline trial. However, the Trial 3 loudness ratings of these subjects were slightly but significantly higher than their Trial 2 loudness ratings. For the control subjects, Trial 2 loudness reports were substantially lower than those of either the baseline trial or Trial 3. Furthermore, the Trial 3 ratings of these subjects did not differ significantly from their baseline ratings. In summary, all subjects reported equivalent and substantial hearing loss in response to the deafness suggestion on Trial 2. However, subjects in the three conditions exhibited different patterns of response from Trial 2 to Trial 3. Subjects who received hypnotic deafness suggestions on both Trials 2 and 3 reported equivalent hearing loss on these two trials. Subjects given the demand instruction also reported significant Trial 3 loudness reduction, but to a less degree than that exhibited on Trial 2. In contrast, Trial 3 loudness reports for the control subjects did not differ from their baseline trial reports. Reported deafness and cognitive strategies. A one-way ANOVA performed on the cognitive strategy scores obtained from the open-ended questionnaires was significant, F(2,42) = 5.22, p < .01. Subjects who received the reinforced hypnotic deafness suggestion on Trial 3 attained significantly higher cognitive strategy scores (M = 2.20, SD = .94) than did subjects given the demand instruction (M = 1.47, SD = 1.06) and the control subjects (M = 1.00, SD = 1.07). Those in the latter two groups did not differ significantly in cognitive strategy scores. A one-way ANOVA performed on subjects' scale ratings of strategy use was significant, F(2, 42) = 6.84, p < .01. Post hoc comparisons revealed that both the reinforced hypnosis subjects (M = 6.53, SD =1.51) and the demand instruction subjects (M = 6.60, SD = 1.24) rated themselves as using cognitive strategies to a greater extent than did the control subjects (M = 4.60, SD = 2.16). The strategy use ratings of demand instruction Table 1 Mean Loudness Ratings by Group Trial 1
Trial 2
Trial3
Group
M
SD
M
SD
M
SD
Hypnosis Demand Instruction Control
14.27 13.47 14.93
3.49 4.02 3.13
10.40 8.07 10.80
4.66 2.71 3.99
9.27 10.87 15.87
5.02 4.57 3.78
HYPNOSIS, COMPLIANCE AND HALLUCINATION subjects failed to differ significantly from the ratings of subjects in the hypnosis condition.
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Discussion Our findings replicate those of earlier studies (Spanos et al, in press; Spanos et al., 1990) and provide strong support for the hypothesis that reports of suggestion-induced perceptual alteration proffered by highly hypnotizable hypnotic subjects reflect, to a substantial degree, reporting biases rather than actual changes in perceptual processing. In addition, the present findings indicate that the increase in loudness reported from Trial 2 (hypnotic deafness) to Trial 3 (demand instruction) by subjects given the demand manipulation cannot be explained in terms of repeated exposure to the tone. Subjects who were given the hypnotic suggestion before Trial 2 and again before Trial 3 continued to report the same low levels of loudness on both trials. These findings indicate that hypnotic suggestions were slightly but significantly more potent at inducing reports of deafness than was the demand instruction employed in this research. These findings might mean that Trial 2 loudness reduction scores reflect a small perceptual alteration component that was added to a reporting bias component. Alternatively, these findings might simply mean that hypnotic suggestions contained stronger demands to bias perceptual reports than did our demand instruction. Regardless of which hypothesis eventually proves true, the present findings clearly support Wagstaff's (1981,1986) contention that suggestion-induced reporting bias is a central component in hypnotic responding. Subjects given the deafness suggestion before Trial 3 reported more use of cognitive strategies in their open-ended reports than did either control subjects or subjects given the demand instruction. As already mentioned, only subjects given the Trial 3 suggestion maintained equivalent levels of reported loudness reduction across Trials 2 and 3. One interpretation of these findings is that strategy use led to the greater-than-demand loudness reductions in subjects given the Trial 3 suggestion. On the other hand, these findings could indicate that subjects who received the Trial 3 suggestion were particularly likely to indicate strategy use because only these subjects had been given a suggestion that explicitly instructed them to use strategies on Trial 3. The open-ended questionnaires, by themselves, contained few cues that strategy reporting was required. Consequently, most subjects given the demand instruction may have been unaware that such reporting was called for. However, when these subjects were given the final Likert-type scale that explicitly asked them to rate the extent of their strategy use, their ratings on this dimension were as high as those of the subjects given the Trial 3 deafness suggestion. In other words, subjects were quite willing to bias their reports of strategy use as well as their loudness reports. However, such biasing was unlikely to occur in the demand instruction condition until these subjects were provided (via an explicit questionnaire) with the requisite information about the responses called for. Such information was provided by the suggestion for those subjects who received a suggestion before Trial 3. Consequently, for subjects in this condition, open-ended reports of strategy use and the relationship between such reports and reported loudness reductions remain ambiguous. It would be of interest in a future
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study to administer deafness suggestions that did not provide cognitive strategies. If subjects who received these suggestions continued to report greater strategy use on open-ended questionnaires and greater loudness reductions on Trial 3 than subjects given a demand instruction, support would be provided for the hypothesis that strategy use produces effects on perceptual reports above and beyond the effects of reporting bias.
Experiment 2 Negative visual hallucinations are suggestion-induced reports of an inability to see a target stimulus. Negative visual hallucination suggestions are among the most difficult items on standardized hypnotizability scales (Hilgard, 1965) and are usually "passed" by only highly hypnotizable subjects. Although relatively little empirical work has focused on negative visual hallucinations, some evidence indicates that reporting bias may play a prominent role in this phenomenon. Spanos, Flynn, and Gabora (1989) gave highly hypnotizable subjects the suggestion that, on opening their eyes, they would see only a blank piece of paper. In fact, the number 8 was displayed prominently on the paper. Subjects who reported seeing nothing on the paper were interviewed by a second experimenter, who implied to them that seeing nothing was the response typically given only by fakers, whereas seeing a figure that gradually faded over 1 min was typical of truly hypnotized people. Subjects were then given the opportunity to draw what they had seen on the paper at successive points after they had opened their eyes. Under these circumstances, 14 out of 15 subjects who had initially insisted that they saw nothing on the paper now drew a number 8 as the figure seen when they first opened their eyes. In other words, when demands to report having "seen nothing" were lifted, almost all of these highly hypnotizable subjects acknowledged through their drawings that they had seen the target figure they had earlier denied seeing. These findings do not mean that subjects in the Spanos et al. (1989) experiment failed to experience any perceptual distortion after the suggestion. By employing simple ocular strategies such as unfocusing the eyes, or averting gaze from the target stimulus, subjects can easily produce blurring and other distortions of visual perception. Subjects in the Spanos et al. experiment and in other experiments on negative hallucination may well have employed such strategies to induce perceptual distortions. Nevertheless, Spanos et al.'s findings suggest that, regardless of any such distortions in perception, subjects clearly exaggerated their experiences in line with suggested demands by stating that they could see nothing on the paper. Although hypnotic subjects are exposed to explicit demands to gear their reports in line with the requests of suggestions, they are also exposed to implicit demands to report honestly and accurately about their experiences (deGroot & Gwynn, 1989; Spanos, 1986). Furthermore, hypnotic subjects are likely to differ substantially in the extent to which they are sensitive to norms for honest reporting. Consequently, such subjects are likely to exaggerate and distort their experiences to different degrees in response to experimental demands. Although the Spanos et al. (1989) study indicated that negative hallucinators exaggerate their experiences in terms of sug-
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gested demands, it provided no means of assessing individual differences in the degree of such reporting bias. Moreover, neither Spanos et al. nor other researchers have assessed the cognitive strategies that subjects employ in order to distort their perceptual experiences and define themselves as "not seeing." In Experiment 2, we assessed the strategies for "not seeing" that subjects reported in response to a negative visual hallucination suggestion and examined the relationship between the use of such strategies and the degree to which subjects reported blindness. In addition, the role of reporting bias in negative visual hallucination responding was assessed by testing subjects in the deafness paradigm described in Experiment 1 and examining the relationship between bias scores obtained in that paradigm and blindness scores obtained in response to a negative visual hallucination suggestion. We anticipated that reporting bias in the deafness paradigm would correlate significantly with reports of blindness after the suggestion for negative visual hallucination. Method Subjects. Forty-nine Carleton University undergraduates volunteered to participate in a study of perception and hypnosis. These subjects had previously tested as either medium (scores of 3 or 4) or high (scores of 5-7) on the CURS&O (Spanos et al., 1983). All subjects received course credit for their participation. Procedure. All subjects were tested individually by the same male experimenter in two sessions. In the first session subjects were asked to close their eyes and were administered the 10-min hypnotic induction procedure used in Experiment 1. This was followed by a suggestion for blindness that informed subjects that they were to become actively involved in the suggestion and were to use whatever strategies they could to make a word disappear from a piece of paper. Subjects were then instructed to look at an 8.5 in. X 11 in. sheet of white paper that was held approximately 50 cm in front of their eyes. On the paper was printed the word DINOSAUR in letters 20 mm in height. The suggestion instructed subjects to notice that the word was fading more and more, until it completely disappeared and the paper was blank. They were then asked to describe what they saw on the paper. Following Bryant and McConkey (1989), subjects who reported seeing all or part of the word DINOSAUR were given a prompt that encouraged them to try harder and to use whatever strategies they could to make the word fade and disappear. After the prompt, these subjects were again asked what they saw on the paper. After their verbal reports, a wake-up procedure was administered and the blindness suggestion was canceled. Blindness scores were computed as follows. Subjects who in their initial descriptions reported seeing nothing on the paper were given a blindness score of 2. Subjects who initially reported seeing all or part of the word but reported complete blindness after the prompt received a score of 1. Finally, subjects who failed to report blindness despite the prompt received a score of 0. Subjects were next administered a 5-point scale asking them to rate the extent of their blindness. Scale alternatives ranged from not at all (0) to completely (4). After completion of this hypnotic blindness selfrating, subjects wrote responses to a one-page, open-ended questionnaire that asked them what, if anything, they had done in order to "not see" the word. This questionnaire was scored for cognitive strategy use by two independent judges who were unaware of subjects' experimental condition and level of hypnotizability. Judges scored each subject as reporting strategy use (1) or not reporting strategy use (0). Judges agreed 92% of the time, and discrepancies were resolved through discussion. Finally, the subjects were given a list of seven possible strategies and
were asked to circle as many as they had used in their attempt to make the word disappear. These strategies were listed as follows: 1. I unfocused my eyes. 2. I crossed my eyes. 3. I looked above, below, or away from the word, rather than looking right at it. 4. I created a visual image to cover or block the word. 5. I tried to imagine a different word. 6. I tried to think of other things, so as not to notice the word. 7. Other (specify). Subjects were tested in a second individual session within 2 weeks of the first. During the second session, 34 subjects were administered the deafness paradigm with the demand instruction after Tone 3 in the same manner as in Experiment 1. The remaining 15 subjects were administered the control sequence of the paradigm. After their loudness ratings all subjects were administered two open-ended questionnaires taken from Experiment 1 (Questionnaires 1 and 3) that assessed reported strategy use during the Trial 3 tone. Subjects were scored 2 if they reported strategy use on the first questionnaire, 1 if they reported strategy use on the second questionnaire, and 0 if they failed to report strategy use on either questionnaire. Two independent judges agreed on these ratings 92% of the time. Results Compliance and control. A Hotelling's T2 analysis that compared the scores of Session 2 experimental and control subjects on the CURSS dimensions, open-ended blindness reports, blindness scale self-ratings, and judges' blindness strategy use ratings failed to approach significance. Thus subjects in the demand instruction and control conditions were equivalent on these measures. Session 2 experimental effects. A 2 X 3 (Condition [demand instruction or control] X Trial [1, 2, or 3]) mixed ANOV\ on loudness ratings yielded a significant interaction, F(2, 94) = 3.88, p < .025, that was analyzed further in terms of simple main effects. As shown in Table 2, the simple main effects for condition at Trials 1 and 2 failed to approach significance, indicating that subjects in the demand instruction and control conditions of Session 2 reported equivalent levels of loudness on these two trials. However, a significant simple main effect was found for condition at Trial 3, F(l, 70) = 6.28, p < .025. Subjects who received the demand instruction reported significantly lower Trial 3 loudness ratings than did the nondemand (control) subjects. Analyses within conditions revealed that significant changes in the loudness of the tone across trials were reported by subjects given the demand instruction, F(2,94) = 30.14, p< .001, and also by subjects not given the demand instruction (con-
Table 2 Mean Loudness Ratings for Demand Instruction and Control Subjects Trial 1
Trial 2
Trial 3
Subjects
M
SD
M
SD
M
SD
Demand Instruction Control
13.29 14.20
3.94 3.65
9.47 10.20
3.32 4.02
11.44 14.40
3.82 4.42
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HYPNOSIS, COMPLIANCE AND HALLUCINATION trols), F(2, 94) = 20.42, p < .001. Post hoc comparisons (least significant difference) indicated that subjects given the demand instruction reported significant loudness reductions on Trial 2 (suggested deafness) and on Trial 3 (demand instruction). However, Trial 3 reported loudness reductions were significantly smaller than those of Trial 2. The nondemand subjects reported significantly lower loudness on Trial 2 than on Trial 1 or 3. Loudness ratings on Trials 1 and 3 failed to differ significantly. Reporting bias in "blind" and"not blind"subjects. Analyses of relationships between Session 2 reporting bias and response to the Session 1 negative visual hallucination suggestion included only those subjects who were administered the demand instruction in Session 2. For each of these subjects, a Session 2 reporting bias score was obtained by subtracting their Trial 3 (demand instruction) loudness score from their Trial 1 score. We anticipated that subjects who reported complete blindness in Session 1 would report greater Session 2 reporting bias then subjects who reported little or no blindness in Session 1. This hypothesis was tested in an analysis that included only those subjects who rated themselves as exhibiting complete blindness (self-rating of 4, n = 11) or little or no blindness (selfrating of 1 or 0,« = 9) in Session 1. As predicted, subjects who reported complete blindness (M = 3.73, SD = 2.65) exhibited substantially and significantly greater Session 2 reporting bias than those who did not report blindness (M= .33, SD = 3.24), /(18) = 2.58 p < .05. Strategies for blindness and deafness. On the basis of their Session 1 open-ended reports, 40 subjects (82%) were rated as using one or more strategies in an attempt to "not see" the target word. However, in response to the seven-item list of strategies, all subjects reported using at least one strategy. The percentages of subjects who chose each listed strategy are given in Table 3. Twelve subjects (24%) chose Strategy 7 on the strategy checklist, indicating that they had used strategies other than the available choices. Closer examination revealed that 8 of these subjects (67%) reported ocular fixation on only a limited aspect of the stimulus (i.e., staring fixedly at a letter or portion of the word DINOSAUR); 2 subjects (17%) described sensations experienced during the suggestion, such as a blurriness of vision, rather than reporting a specific strategy; 1 subject reiterated that he had visualized a piece of white paper covering the
Table 3 Number and Percentage of Subjects Who Reported Using Each Strategy Strategy
1.
2. 3. 4. 5. 6. 7.
I unfocused my eyes. I crossed my eyes. I looked above, below, or away from the word, rather than looking right at it. I created a visual image to cover or block the word. I tried to imagine a different word. I tried to think of other things, so as not to notice the word. Other (specify).
No. of subjects
%
33 7
67 14
29
59
13 4
27 8
6 12
12 24
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word (Strategy 4); and the remaining subject simply reported "I blanked my mind." A t test comparing Session 2 demand instruction and control subjects on auditory strategy scores obtained from the openended questionnaires failed to approach significance. As in Experiment 1, subjects who received the demand instruction (M= .74, SD = .57) reported no greater use of cognitive strategies to reduce the loudness of the Trial 3 tone than did control subjects Correlations. Table 4 shows the correlations among the dependent variables assessed in Sessions 1 and 2 for subjects given the demand instruction in Session 2. Difference scores were used to compute Session 2 deafness scores (baseline-Trial 2) and reporting bias scores (baseline-Trial 3). In Session 2, the correlation between Trial 2 deafness scores and Trial 3 reporting bias scores was substantial and indicated that to a large extent subjects who reported high levels of hypnotic deafness were the same persons who, on the next trial, biased their reports in terms of experimental demands. Interestingly, the extent to which subjects biased their reports on Trial 3 also correlated significantly with the extent to which they reported use of cognitive strategies on that trial. In other words, subjects who biased their reports of hearing reduction to a relatively large degree also tended to be attuned enough to experimental demands to generate reports of strategy use on the basis of the minimal cues provided by the open-ended questionnaires. In Session 1, the correlation between open-ended reports of blindness and self-ratings of blindness was very high and supports the notion that these two indexes assessed the same response dimension. Neither of these Session 1 blindness indexes correlated significantly with the extent of strategy use reported by subjects in response to the negative visual hallucination suggestion. On the other hand, both Session 1 blindness indexes correlated significantly with Session 2 deafness ratings and reporting bias scores. More important, the partial correlations between deafness ratings and open-ended reports of blindness, r(31) = .03, and between deafness ratings and self-ratings of blindness, r(31) = .22, were not significant when the effects of reporting bias scores were statistically controlled. Reporting bias scores, like blindness scores, did not correlate significantly with the extent of subjects' strategy use in response to the Session 1 suggestion. Taken together, these findings indicate that reporting bias influenced response to suggestions for negative visual hallucination as well as response to deafness suggestions. Moreover, the correlation between reports of suggested blindness and deafness was mediated by subjects' tendency to bias their perceptual reports in terms of suggested demands.
General Discussion The findings of Experiment 2 concerning suggested deafness replicate those of Experiment 1 as well as those of Spanos et al. (in press) and indicate that demand-induced reporting bias plays an important role in the phenomenon of hypnotic deafness. The results of Experiments 1 and 2 further indicate that compliance pressures lead subjects to bias their reports of auditory strategy use as well as their reports of reduced hearing. When assessment procedures explicitly implied that the report-
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SPANOS, BURGESS, CROSS, AND MACLEOD
Table 4 Correlations Among Session 1 and Session 2 Dependent Variables in Experiment 2 Variable 1. 2. 3. 4. 5. 6.
Suggested deafness Reporting bias Deafness strategies Judges' blindness ratings Self-ratings of blindness Blindness strategies
1
.79**
.39* .35*
.31* .37* .03
.42** .38* .03 .82**
.04 .02 .11 .04 .04
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