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Hypnotic responding and the Five Factor Personality Model: Hypnotic analgesia and Openness to Experience
Journal of Research in Personality 47 (2013) 128–131
Contents lists available at SciVerse ScienceDirect
Journal of Research in Personality journal homepage: www.elsevier.com/locate/jrp
Brief Report
Hypnotic responding and the Five Factor Personality Model: Hypnotic analgesia and Openness to Experience Leonard S. Milling ⇑, Danielle S. Miller, Danelle L. Newsome, Emily S. Necrason University of Hartford, West Hartford, CT, USA
a r t i c l e
i n f o
Article history: Available online 25 October 2012 Keywords: Hypnosis Pain Individual differences Openness to Experience Five Factor Personality Model
a b s t r a c t This study evaluated Openness to Experience as a moderator of the effect of hypnosis on pain. Four hundred and sixty-one introductory psychology students were randomly assigned to analogue versions of hypnotic analgesia, cognitive-behavioral, or placebo-control pain treatments. Thereafter, participants completed a questionnaire measure of the Big Five factors. Openness to Experience moderated the effect of treatment condition. Openness was more strongly related to the relief produced by our hypnotic analgesia condition than to the relief generated by our cognitive-behavioral and placebo-control conditions. This study is the first to clearly place individual differences in hypnotic pain reduction, and by extension, individual differences in hypnotic responding, within the broad domain of the Openness to Experience factor of the Five Factor Personality Model. Ó 2012 Elsevier Inc. All rights reserved.
1. Introduction There are large individual differences in responding to hypnosis (Gwynn & Spanos, 1996). Commonly, these individual differences are measured using standardized hypnotic suggestibility scales consisting of a hypnotic induction and a series of test suggestions. The number of test suggestions to which a person responds provides an index of his or her level of suggestibility. Research with these scales has demonstrated that hypnotic suggestibility is associated with responding to a variety of specific suggestions (see de Groh, 1989). Perhaps the most robust of these associations is with suggestions for hypnotic analgesia (see Montgomery, DuHamel, & Redd, 2000). However, few personality traits have been shown to be associated with hypnotic responding or standardized measures of hypnotic suggestibility. Absorption and fantasy-proneness are exceptions to this pattern. Absorption is the tendency to become immersed in a variety of sensory and imaginative experiences (Tellegen & Atkinson, 1974). Fantasy-proneness is the preference for intense imaginative involvements in reading, watching movies and television programs, play activities, and mystical/religious experiences (Lynn & Rhue, 1986). Attempts to identify associations between hypnotic responding and other personality traits have not been fruitful. For example, a number of studies examined associations between hypnotic suggestibility and the Five Factor Personality ⇑ Corresponding author. Address: University of Hartford, Department of Psychology, 200 Bloomfield Avenue, West Hartford, CT 06117, USA. E-mail address: [email protected] (L.S. Milling). 0092-6566/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jrp.2012.10.006
Model. Conceptually, Openness to Experience appears to be the Big Five factor most closely related to hypnotic responding. Openness is the tendency to have an active imagination, preference for variety, and intellectual curiosity. Nordenstrom, Council, and Meier (2002) reported small, but significant correlations between Openness and suggestibility (r = .18 and r = .16). Likewise, Glisky, Tataryn, Tobias, Kihlstrom, and McConkey (1991) noted a weak, but significant association between these variables (r = .16). On the other hand, Glisky and Kihlstrom (1993) found that suggestibility was weakly correlated with 12 items draw from the Tellegen Absorption scale (r = .15), and not at all with Intellectance (comparable to the Openness to Ideas facet) and Liberalism (comparable to a combination of the Openness to Values and Actions facets). Furthermore, several studies failed to show an association between suggestibility and Openness as measured by NEO PIR (Green, 2004), the NEO (Radtke & Stam, 1991) or the NEO-FFI (Malinoski & Lynn, 1999). All in all, the literature is conflicted and when significant correlations are obtained, they are quite small, typically accounting for less than 4% of the shared variance. To our knowledge, there has been no research examining associations between Openness and responding to specific hypnotic suggestions, such as hypnotic analgesia. The purpose of this study was to evaluate the moderator function of Openness to Experience in hypnotic pain reduction. We compared analogue versions of a hypnotic analgesia treatment, a cognitive-behavioral treatment, and a placebo-control condition in reducing experimental pain, and also administered a measure of the Big Five factors. We hypothesized that Openness would be more strongly related to the effect of our hypnotic analgesia condition than to the effect of our cognitive-behavioral and placebo-control conditions.
L.S. Milling et al. / Journal of Research in Personality 47 (2013) 128–131
2. Method
129
During the intervention phase, an experimenter working live administered the glove analgesia suggestion during the posttrial.
2.1. Participants Participants in the study were 167 male and 294 female introductory psychology students who took part to satisfy a course requirement. The mean age of participants was 19.54 (SD = 3.36, range = 16–48). Seventy-one percent of the sample described themselves as Caucasian, 16% as African–American, 7% as Hispanic, 2% as Asian or Pacific Islander, 1% as American Indian or Alaskan native, and 5% as other. 2.2. Apparatus Finger pressure pain was administered using a Forgione–Barber Strain Gauge Pain Stimulator (Forgione & Barber, 1971). This apparatus consists of a doughnut-shaped weight (900 g) attached to a bar (231 g) that pivots from a hinged support stand at the far end. Participants place their index finger on top of a 5-cm finger stand in the middle of the device and their other fingers rest on a platform between the finger stand and the support stand. The bar is about 2 mm wide where it contacts the index finger. When the bar is lowered onto the index finger, it produces 2041 g of force. 2.3. Instruments 2.3.1. Pain intensity rating Pain intensity was measured on an 11-point visual analog scale ranging from 0 (no pain at all) to 10 (pain as intense as one can imagine). An 18-cm line showing the eleven numbers and verbal anchors was displayed in a placard in front of participants. When participants placed their finger in the stimulator, an audiotape prompted them to report a whole number reflecting pain intensity every 20 s for one min. The sum of these reports yielded an index of overall intensity ranging from 0 to 30. Baseline intensity ratings were obtained before treatment and postintensity ratings were made while participants utilized a pain control intervention. Cronbach’s alpha was .94 for both baseline intensity and postintensity ratings. 2.3.2. NEO Personality Inventory-Revised (NEO PI-R; Costa & McRae, 1992). The NEO PI-R is a 240-item selfreport measure of the Five Factor Personality Model. Each of the 240 items is rated on a 5-point scale ranging from strongly agree to strongly disagree. The 48 items comprising the Openness to Experience scale tap the tendency to have an active imagination, aesthetic sensitivity, preference for variety, and intellectual curiosity. Cronbach’s alpha is reported to be .87 and validity is suggested by correlations with alternative measures of Openness (Costa & McRae, 1992). 2.4. Analogue treatment conditions The three analogue treatments were delivered in two phases. During the preparation phase, participants heard information about pain management and were given an opportunity to practice or experience an intervention without placing their finger in the stimulator. Then, during the intervention phase, participants were helped to utilize the intervention while placing their finger in the stimulator and making postintensity ratings. 2.4.1. Hypnotic analgesia condition During the preparation phase, the 67 males and 115 females assigned to this condition listened to an audiotape presenting information designed to correct misconceptions about hypnosis, a hypnotic induction, and an opportunity to practice a 45-s glove analgesia suggestion (see Milling, Reardon, & Carosella, 2006).
2.4.2. Cognitive-behavioral condition During the preparation phase, the 51 males and 81 females assigned to this condition listened to an audiotape presenting information about the gate control theory of pain, as well as information and practice in the use of progressive muscle relaxation, guided imagery, and coping self-statements (see Milling et al., 2006). During the intervention phase, an experimenter working live helped participants to use these techniques during the posttrial. 2.4.3. Placebo-control condition The placebo consisted of an inert solution described to participants as an experimental topical analgesic. During the preparation phase, the 49 male and 98 female participants assigned to this condition heard information about the nature of medical analgesics. During the intervention phase, participants made postintensity ratings with the solution applied to their index finger. 2.5. Procedure Participants were recruited to take part in a study comparing an experimental topical analgesic with psychological pain control techniques. To begin, participants provided written informed consent and completed a medical screening form. Eligible participants could not have a medical condition that affected the sensitivity of their left index finger or an allergy to the placebo solution. Participants assigned to the hypnotic analgesia condition were not told the study involved hypnosis until after the baseline trial to prevent a hold-back effect (Zamansky, Scharf, & Brightbill, 1964). In a hold-back effect, participants exaggerate the pain on the baseline trial to leave room for improvement on the posttrial due to the effects of hypnosis. Participants in the cognitive-behavioral and placebo-control conditions were not told the experiment involved hypnosis until the study was over to prevent them from mistakenly concluding they were somehow being hypnotized. To further minimize the chance that participants assigned to the cognitive-behavioral and placebo-control conditions might incorrectly assume they were being hypnotized, all cues associated with hypnosis (e.g., books) were removed from the lab. Each participant was run through the experiment individually by two experimenters. One experimenter delivered the analogue treatments and the other administered the NEO PI-R. This was intended to reduce the demand on participants to respond consistently across the two parts of the experiment. Each experimenter was blind to information collected during the part of the experiment he or she had not run. In the initial part of the study, the first experimenter provided the analogue treatments. During the baseline trial, participants placed their left index finger in the stimulator and made baseline intensity ratings once every 20 s for one min. Each participant was then randomly assigned to one of the three experimental conditions and underwent the preparation and intervention phases of treatment. During the intervention phase, participants placed their finger in the stimulator and made postintensity ratings every 20 s for one min. At this point, the participant was escorted to another room where the second experimenter administered the NEO PI-R. 3. Results 3.1. Preliminary analyses Pain intensity ratings yielded mean scores of 13.74 (SD = 6.01; range = 0–30) at baseline and 11.07 (SD = 6.09; range = 0–30) at
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L.S. Milling et al. / Journal of Research in Personality 47 (2013) 128–131
post. Openness to Experience ratings produced a mean score of 117.57 (SD = 18.49; range = 53–168). Means and standard deviations for these variables by treatment condition are shown in Table S1 in the Supplementary materials. 3.2. Reduction of pain intensity A one-way analysis of covariance (ANCOVA) on postintensity ratings, with baseline intensity ratings as the covariate, produced a significant main effect for treatment condition, F (2457) = 57.14, p < .001, eta2 = .20. A least significant difference test (LSD) on estimated marginal means with a Bonferroni adjustment for the number of statistical comparisons revealed that participants in the placebo-control condition reported more intense pain (adjusted mean = 13.87) than those in the cognitive-behavioral (adjusted mean = 9.89) and hypnotic analgesia (adjusted mean = 9.65) conditions. The difference between the cognitivebehavioral and hypnotic analgesia conditions was not significant. Within condition, paired-comparisons of baseline and post intensity ratings indicated that baseline to post decreases in intensity were significantly different from 0 for the hypnotic analgesia (t181 = 11.10, p < .001) and cognitive-behavioral (t131 = 11.43, p < .001) conditions. However, baseline to post changes in intensity in the placebo-control condition were not significantly different from 0 (t146 = 0.30, ns). 3.3. Moderator analysis of Openness to Experience We hypothesized that Openness to Experience would be more strongly related to the relief produced by the hypnotic intervention than to the relief produced by the cognitive-behavioral and placebo interventions. The Baron and Kenny (1986) analytic strategy for testing moderation involves examining whether there is an interaction between the hypothesized moderator and the independent variable. Accordingly, we performed three simultaneous regressions and tested the interaction of Openness and treatment condition in predicting pain reduction. In each analysis, we regressed postintensity on baseline intensity, Openness, treatment condition, and the interaction of Openness and treatment condition. Table 1 shows the results of these regressions. In the first regression, we compared the effects of our hypnotic analgesia condition with that of a cluster of our cognitive-behavioral and placebo-control conditions. After controlling for baseline intensity, postintensity was predicted by Openness and the interaction of condition and Openness. This suggests that the effect of the hypnotic condition was moderated by Openness to Experience.
Table 1 Simultaneous regressions testing moderation of effects of treatment condition by Openness to Experience. Comparison and predictor
F
p<
Beta
Eta2
Hypnotic vs. cognitive-behavioral and placebo Baseline intensity 486.97 Openness to Experience (O) 13.41 Treatment condition (TC) 1.25 TC O 4.24
.001 .001 .265 .040
.70 .05 .23 .43
.52 .03 .00 .01
Hypnotic vs. cognitive-behavioral Baseline intensity Openness to Experience (O) Treatment condition (TC) TC O
334.03 8.03 4.00 4.48
.001 .005 .046 .035
.71 .03 .50 .54
.52 .03 .01 .01
Hypnotic vs. placebo Baseline intensity Openness to Experience (O) Treatment condition (TC) TC O
365.07 10.80 0.10 3.32
.001 .001 .750 .069
.67 .05 .07 .42
.53 .03 .20 .01
Fig. 1. Interaction of Openness to Experience and treatment condition on residualized pain intensity change scores.
In the second regression, we compared the effects of our hypnotic analgesia condition with that of our cognitive-behavioral condition. After controlling for baseline intensity, postintensity was predicted by Openness, condition, and the interaction of condition and Openness. Once again, this suggests that the hypnotic condition was moderated by Openness to Experience. In the third regression, we compared the effects of our hypnotic analgesia condition with our placebo-control condition. After controlling for baseline intensity, postintensity was predicted only by the main effect of Openness. However, the interaction of condition and Openness approached significance (p = .069). Fig. 1 summarizes the interaction of Openness and treatment condition in the three regressions. Residualized change scores in pain intensity were generated by regressing postintensity on baseline intensity. A scatterplot of residualized change scores and Openness was created, and a regression line was generated for each of the three conditions. Fig. 1 shows that higher levels of Openness were associated with more pain reduction in the hypnotic analgesia condition than in the cognitive-behavioral and placebo-control conditions. Figs. S1, S2, and S3 in the Supplementary materials show the scatterplots of Openness and residualized change scores, as well as the regression lines for the hypnotic analgesia, cognitivebehavioral, and placebo-control conditions respectively. The NEO PI-R Openness to Experience scale is composed of six facet subscales: Openness to Fantasy, Aesthetics, Feelings, Actions, Ideas, and Values. When the three simultaneous regressions were repeated substituting each of the facet scores in turn for the overall Openness score, only the Openness to Aesthetics facet subscale showed a significant interaction with treatment condition in predicting pain reduction. Table S2 in the Supplementary materials shows the results of the three regressions for the Openness to Aesthetics facet subscale.
4. Discussion We found a clear relationship between Openness to Experience and responding to hypnosis. Specifically, Openness moderated the effect of our hypnotic analgesia suggestion. The relationship between Openness and pain reduction was stronger in our hypnotic analgesia condition than in our cognitive-behavioral and placebocontrol conditions. This moderator effect appears to have been carried primarily by the Openness to Aesthetics facet.
L.S. Milling et al. / Journal of Research in Personality 47 (2013) 128–131
In contrast, past research has reported weak (Glisky et al., 1991; Nordenstrom et al., 2002) or nonexistent (Glisky & Kihlstrom, 1993; Green, 2004; Malinoski & Lynn, 1999; Radtke & Stam, 1991) relations between Openness and hypnotic suggestibility. Why were we able to demonstrate a relationship between Openness and hypnotic pain reduction when past research has generally failed to show clear associations between Openness and hypnotic suggestibility? Perhaps our use of an experimental manipulation and moderator analysis made it easier to identify a relationship than the correlational approach employed in past research. Another possible explanation involves the difference between our hypnotic analgesia suggestion and kind of suggestions typically comprising hypnotic suggestibility scales. There are three types of hypnotic suggestions. In an ideomotor suggestion, the person is invited to experience a motor movement. In a challenge suggestion, the person is told he or she will not be able to perform a particular behavior and then is asked to carry out the prohibited action. In a cognitive suggestion, the person is invited to experience an alteration in cognitive functioning. Thus, ideomotor and most challenge suggestions tend to focus on the performance or inhibition of a motor movement. Cognitive suggestions focus more on alterations in sensations, perceptions, thoughts, and feelings. Our hypnotic analgesia suggestion (i.e., ‘‘your hand is becoming more and more numb. . . more and more insensitive. . . as if it were covered in a thick, thick glove. . . you may not be able to feel anything at all through that glove on your hand. . .’’) is an example of a cognitive suggestion. Of note, standardized hypnotic suggestibility scales typically consist of a mix of ideomotor, challenge, and cognitive test suggestions. Perhaps we were able to identify a clear association between Openness and hypnotic responding because the content of some of the items on the NEO PI-R Openness to Aesthetics scale (e.g., ‘‘Sometimes when I am reading poetry or looking at a work of art, I feel a chill or wave of excitement‘‘) is similar to the experience of cognitive suggestions like hypnotic analgesia. In contrast, items on the Openness to Aesthetics scale seem less similar to the experience of ideomotor and challenge suggestions, which comprise the majority of test suggestions on standardized suggestibility scales. Indeed, the measure of hypnotic suggestibility (i.e., the Harvard Group Scale of Hypnotic Susceptibility) used in all past research in this area is composed almost exclusively of ideomotor and challenge suggestions. Demonstrating that Openness to Experience moderated the effect of our hypnotic treatment has important theoretical implications. This is the first study to clearly place individual differences in hypnotic behavior within the sphere of one of the Big Five factors. Most individual differences variables are embedded in a rich network of constructs. In contrast, hypnosis has been characterized as a field lacking a nomological network (Nadon, 1997). Showing that Openness was more strongly related to the effect of our hypnotic analgesia condition than to that of our non-hypnotic conditions suggests that hypnotic responding may be subsumed within the nomological net of Openness to Experience. Our results may also have useful clinical implications. Pain patients scoring high on Openness to Experience might be good candidates for hypnotic pain interventions. It is sometimes recommended that hypnotic suggestibility be assessed when hypnosis is considered as a treatment. However, administering a standardized measure of hypnotic suggestibility can be timeconsuming and requires the services of a professional who is skilled in hypnosis. Alternatively, Openness can assessed in a relatively brief period of time using standardized paper and pencil measures that do not require the presence of a professional hypnotist. Future research might beneficially explore whether Openness moderates the effect of hypnosis on clinical pain.
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Some limitations of this study should be noted. First, participants completed the NEO PI-R after they were administered the pain interventions. It is possible that among participants assigned to the hypnotic analgesia condition, the experience of the analgesia suggestion affected subsequent responses on the NEO PI-R, thereby accounting for the moderator effect. Second, our sample overrepresented females and young people relative to their numbers in the general population. Finally, compared with clinical pain, the experimental pain stimulus used in this study was relatively mild and had no health implications. In sum, we found that our hypnotic analgesia condition was moderated by Openness to Experience. The relationship between Openness and pain reduction was stronger in our hypnotic analgesia condition than in the non-hypnotic conditions. Our study is the first to clearly place individual differences in hypnotic pain reduction, and by extension, individual differences in hypnotic responding, within the broad domain of the Openness to Experience factor of the Five Factor Personality Model. A logical progression in this line of inquiry would involve exploring interrelationships of Openness to Experience, absorption, fantasy-proneness, hypnotic suggestibility, and responding to suggestions for hypnotic analgesia. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jrp.2012.10.006. References Baron, R. M., & Kenny, D. A. (1986). The moderator-mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations. Journal of Personality and Social Psychology, 51, 1173–1182. Costa, P. T., & McRae, R. R. (1992). Revised NEO Personality Inventory (NEO PI-R) and Neo Five-Factor Inventory (NEO-FFI) Professional Manual. Odessa, FL: Psychological Assessment Resources. de Groh, M. (1989). Correlates of hypnotic susceptibility. In N. P. Spanos & J. F. Chaves (Eds.), Hypnosis: The Cognitive-Behavioral Perspective (pp. 32–63). Amherst, NY: Prometheus Books. Forgione, A. G., & Barber, T. X. (1971). A strain-gauge pain stimulator. Psychophysiology, 8, 102–106. Glisky, M. L., & Kihlstrom, J. F. (1993). Hypnotizability and facets of openness. International Journal of Clinical and Experimental Hypnosis, 41, 112–123. Glisky, M. L., Tataryn, D. J., Tobias, B. A., Kihlstrom, J. F., & McConkey, K. M. (1991). Absorption, openness to experience, and hypnotizability. Journal of Personality and Social Psychology, 60, 263–272. Green, J. P. (2004). The five factor model of personality and hypnotizability. Little variance in common. Contemporary Hypnosis, 21, 161–168. Gwynn, M. I., & Spanos, N. P. (1996). Hypnotic responsiveness, nonhypnotic suggestibility, and responsiveness to social influence. In R. G. Kunzendorf, N. P. Spanos, & B. Wallace (Eds.), Hypnosis and Imagination (pp. 147–175). Amityville, NY: Baywood Publishing. Lynn, S. J., & Rhue, J. W. (1986). The fantasy-prone person: Hypnosis, imagination, and creativity. Journal of Personality and Social Psychology, 51, 404–408. Malinoski, P. T., & Lynn, S. J. (1999). The plasticity of early memory reports: Social pressure, hypnotizability, compliance and interrogative suggestibility. International Journal of Clinical and Experimental Hypnosis, 47, 320–345. Milling, L. S., Reardon, J. M., & Carosella, G. M. (2006). Mediation and moderation of psychological pain treatments: Response expectancies and hypnotic suggestibility. Journal of Consulting and Clinical Psychology, 74, 253–262. Montgomery, G. H., DuHamel, K. N., & Redd, W. H. (2000). A meta-analysis of hypnotically induced analgesia: How effective is hypnosis? International Journal of Clinical and Experimental Hypnosis, 48, 138–153. Nadon, R. (1997). What this field needs is a good nomological network. International Journal of Clinical and Experimental Hypnosis, 45, 314–323. Nordenstrom, B. K., Council, J. R., & Meier, B. P. (2002). The ‘Big Five’ and hypnotic suggestibility. International Journal of Clinical and Experimental Hypnosis, 50, 276–281. Radtke, H. L., & Stam, H. J. (1991). The relationship between absorption, openness to experience, anhedonia, and susceptibility. International Journal of Clinical and Experimental Hypnosis, 39, 39–56. Tellegen, A., & Atkinson, G. (1974). Openness to absorbing and self-altering experiences (‘‘absorption’’), a trait related to hypnotic susceptibility. Journal of Abnormal Psychology, 83, 268–277. Zamansky, H. S., Scharf, B., & Brightbill, R. (1964). The effect of expectancy for hypnosis on prehypnotic performance. Journal of Personality, 32, 236–248.
Contents lists available at SciVerse ScienceDirect
Journal of Research in Personality journal homepage: www.elsevier.com/locate/jrp
Brief Report
Hypnotic responding and the Five Factor Personality Model: Hypnotic analgesia and Openness to Experience Leonard S. Milling ⇑, Danielle S. Miller, Danelle L. Newsome, Emily S. Necrason University of Hartford, West Hartford, CT, USA
a r t i c l e
i n f o
Article history: Available online 25 October 2012 Keywords: Hypnosis Pain Individual differences Openness to Experience Five Factor Personality Model
a b s t r a c t This study evaluated Openness to Experience as a moderator of the effect of hypnosis on pain. Four hundred and sixty-one introductory psychology students were randomly assigned to analogue versions of hypnotic analgesia, cognitive-behavioral, or placebo-control pain treatments. Thereafter, participants completed a questionnaire measure of the Big Five factors. Openness to Experience moderated the effect of treatment condition. Openness was more strongly related to the relief produced by our hypnotic analgesia condition than to the relief generated by our cognitive-behavioral and placebo-control conditions. This study is the first to clearly place individual differences in hypnotic pain reduction, and by extension, individual differences in hypnotic responding, within the broad domain of the Openness to Experience factor of the Five Factor Personality Model. Ó 2012 Elsevier Inc. All rights reserved.
1. Introduction There are large individual differences in responding to hypnosis (Gwynn & Spanos, 1996). Commonly, these individual differences are measured using standardized hypnotic suggestibility scales consisting of a hypnotic induction and a series of test suggestions. The number of test suggestions to which a person responds provides an index of his or her level of suggestibility. Research with these scales has demonstrated that hypnotic suggestibility is associated with responding to a variety of specific suggestions (see de Groh, 1989). Perhaps the most robust of these associations is with suggestions for hypnotic analgesia (see Montgomery, DuHamel, & Redd, 2000). However, few personality traits have been shown to be associated with hypnotic responding or standardized measures of hypnotic suggestibility. Absorption and fantasy-proneness are exceptions to this pattern. Absorption is the tendency to become immersed in a variety of sensory and imaginative experiences (Tellegen & Atkinson, 1974). Fantasy-proneness is the preference for intense imaginative involvements in reading, watching movies and television programs, play activities, and mystical/religious experiences (Lynn & Rhue, 1986). Attempts to identify associations between hypnotic responding and other personality traits have not been fruitful. For example, a number of studies examined associations between hypnotic suggestibility and the Five Factor Personality ⇑ Corresponding author. Address: University of Hartford, Department of Psychology, 200 Bloomfield Avenue, West Hartford, CT 06117, USA. E-mail address: [email protected] (L.S. Milling). 0092-6566/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jrp.2012.10.006
Model. Conceptually, Openness to Experience appears to be the Big Five factor most closely related to hypnotic responding. Openness is the tendency to have an active imagination, preference for variety, and intellectual curiosity. Nordenstrom, Council, and Meier (2002) reported small, but significant correlations between Openness and suggestibility (r = .18 and r = .16). Likewise, Glisky, Tataryn, Tobias, Kihlstrom, and McConkey (1991) noted a weak, but significant association between these variables (r = .16). On the other hand, Glisky and Kihlstrom (1993) found that suggestibility was weakly correlated with 12 items draw from the Tellegen Absorption scale (r = .15), and not at all with Intellectance (comparable to the Openness to Ideas facet) and Liberalism (comparable to a combination of the Openness to Values and Actions facets). Furthermore, several studies failed to show an association between suggestibility and Openness as measured by NEO PIR (Green, 2004), the NEO (Radtke & Stam, 1991) or the NEO-FFI (Malinoski & Lynn, 1999). All in all, the literature is conflicted and when significant correlations are obtained, they are quite small, typically accounting for less than 4% of the shared variance. To our knowledge, there has been no research examining associations between Openness and responding to specific hypnotic suggestions, such as hypnotic analgesia. The purpose of this study was to evaluate the moderator function of Openness to Experience in hypnotic pain reduction. We compared analogue versions of a hypnotic analgesia treatment, a cognitive-behavioral treatment, and a placebo-control condition in reducing experimental pain, and also administered a measure of the Big Five factors. We hypothesized that Openness would be more strongly related to the effect of our hypnotic analgesia condition than to the effect of our cognitive-behavioral and placebo-control conditions.
L.S. Milling et al. / Journal of Research in Personality 47 (2013) 128–131
2. Method
129
During the intervention phase, an experimenter working live administered the glove analgesia suggestion during the posttrial.
2.1. Participants Participants in the study were 167 male and 294 female introductory psychology students who took part to satisfy a course requirement. The mean age of participants was 19.54 (SD = 3.36, range = 16–48). Seventy-one percent of the sample described themselves as Caucasian, 16% as African–American, 7% as Hispanic, 2% as Asian or Pacific Islander, 1% as American Indian or Alaskan native, and 5% as other. 2.2. Apparatus Finger pressure pain was administered using a Forgione–Barber Strain Gauge Pain Stimulator (Forgione & Barber, 1971). This apparatus consists of a doughnut-shaped weight (900 g) attached to a bar (231 g) that pivots from a hinged support stand at the far end. Participants place their index finger on top of a 5-cm finger stand in the middle of the device and their other fingers rest on a platform between the finger stand and the support stand. The bar is about 2 mm wide where it contacts the index finger. When the bar is lowered onto the index finger, it produces 2041 g of force. 2.3. Instruments 2.3.1. Pain intensity rating Pain intensity was measured on an 11-point visual analog scale ranging from 0 (no pain at all) to 10 (pain as intense as one can imagine). An 18-cm line showing the eleven numbers and verbal anchors was displayed in a placard in front of participants. When participants placed their finger in the stimulator, an audiotape prompted them to report a whole number reflecting pain intensity every 20 s for one min. The sum of these reports yielded an index of overall intensity ranging from 0 to 30. Baseline intensity ratings were obtained before treatment and postintensity ratings were made while participants utilized a pain control intervention. Cronbach’s alpha was .94 for both baseline intensity and postintensity ratings. 2.3.2. NEO Personality Inventory-Revised (NEO PI-R; Costa & McRae, 1992). The NEO PI-R is a 240-item selfreport measure of the Five Factor Personality Model. Each of the 240 items is rated on a 5-point scale ranging from strongly agree to strongly disagree. The 48 items comprising the Openness to Experience scale tap the tendency to have an active imagination, aesthetic sensitivity, preference for variety, and intellectual curiosity. Cronbach’s alpha is reported to be .87 and validity is suggested by correlations with alternative measures of Openness (Costa & McRae, 1992). 2.4. Analogue treatment conditions The three analogue treatments were delivered in two phases. During the preparation phase, participants heard information about pain management and were given an opportunity to practice or experience an intervention without placing their finger in the stimulator. Then, during the intervention phase, participants were helped to utilize the intervention while placing their finger in the stimulator and making postintensity ratings. 2.4.1. Hypnotic analgesia condition During the preparation phase, the 67 males and 115 females assigned to this condition listened to an audiotape presenting information designed to correct misconceptions about hypnosis, a hypnotic induction, and an opportunity to practice a 45-s glove analgesia suggestion (see Milling, Reardon, & Carosella, 2006).
2.4.2. Cognitive-behavioral condition During the preparation phase, the 51 males and 81 females assigned to this condition listened to an audiotape presenting information about the gate control theory of pain, as well as information and practice in the use of progressive muscle relaxation, guided imagery, and coping self-statements (see Milling et al., 2006). During the intervention phase, an experimenter working live helped participants to use these techniques during the posttrial. 2.4.3. Placebo-control condition The placebo consisted of an inert solution described to participants as an experimental topical analgesic. During the preparation phase, the 49 male and 98 female participants assigned to this condition heard information about the nature of medical analgesics. During the intervention phase, participants made postintensity ratings with the solution applied to their index finger. 2.5. Procedure Participants were recruited to take part in a study comparing an experimental topical analgesic with psychological pain control techniques. To begin, participants provided written informed consent and completed a medical screening form. Eligible participants could not have a medical condition that affected the sensitivity of their left index finger or an allergy to the placebo solution. Participants assigned to the hypnotic analgesia condition were not told the study involved hypnosis until after the baseline trial to prevent a hold-back effect (Zamansky, Scharf, & Brightbill, 1964). In a hold-back effect, participants exaggerate the pain on the baseline trial to leave room for improvement on the posttrial due to the effects of hypnosis. Participants in the cognitive-behavioral and placebo-control conditions were not told the experiment involved hypnosis until the study was over to prevent them from mistakenly concluding they were somehow being hypnotized. To further minimize the chance that participants assigned to the cognitive-behavioral and placebo-control conditions might incorrectly assume they were being hypnotized, all cues associated with hypnosis (e.g., books) were removed from the lab. Each participant was run through the experiment individually by two experimenters. One experimenter delivered the analogue treatments and the other administered the NEO PI-R. This was intended to reduce the demand on participants to respond consistently across the two parts of the experiment. Each experimenter was blind to information collected during the part of the experiment he or she had not run. In the initial part of the study, the first experimenter provided the analogue treatments. During the baseline trial, participants placed their left index finger in the stimulator and made baseline intensity ratings once every 20 s for one min. Each participant was then randomly assigned to one of the three experimental conditions and underwent the preparation and intervention phases of treatment. During the intervention phase, participants placed their finger in the stimulator and made postintensity ratings every 20 s for one min. At this point, the participant was escorted to another room where the second experimenter administered the NEO PI-R. 3. Results 3.1. Preliminary analyses Pain intensity ratings yielded mean scores of 13.74 (SD = 6.01; range = 0–30) at baseline and 11.07 (SD = 6.09; range = 0–30) at
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post. Openness to Experience ratings produced a mean score of 117.57 (SD = 18.49; range = 53–168). Means and standard deviations for these variables by treatment condition are shown in Table S1 in the Supplementary materials. 3.2. Reduction of pain intensity A one-way analysis of covariance (ANCOVA) on postintensity ratings, with baseline intensity ratings as the covariate, produced a significant main effect for treatment condition, F (2457) = 57.14, p < .001, eta2 = .20. A least significant difference test (LSD) on estimated marginal means with a Bonferroni adjustment for the number of statistical comparisons revealed that participants in the placebo-control condition reported more intense pain (adjusted mean = 13.87) than those in the cognitive-behavioral (adjusted mean = 9.89) and hypnotic analgesia (adjusted mean = 9.65) conditions. The difference between the cognitivebehavioral and hypnotic analgesia conditions was not significant. Within condition, paired-comparisons of baseline and post intensity ratings indicated that baseline to post decreases in intensity were significantly different from 0 for the hypnotic analgesia (t181 = 11.10, p < .001) and cognitive-behavioral (t131 = 11.43, p < .001) conditions. However, baseline to post changes in intensity in the placebo-control condition were not significantly different from 0 (t146 = 0.30, ns). 3.3. Moderator analysis of Openness to Experience We hypothesized that Openness to Experience would be more strongly related to the relief produced by the hypnotic intervention than to the relief produced by the cognitive-behavioral and placebo interventions. The Baron and Kenny (1986) analytic strategy for testing moderation involves examining whether there is an interaction between the hypothesized moderator and the independent variable. Accordingly, we performed three simultaneous regressions and tested the interaction of Openness and treatment condition in predicting pain reduction. In each analysis, we regressed postintensity on baseline intensity, Openness, treatment condition, and the interaction of Openness and treatment condition. Table 1 shows the results of these regressions. In the first regression, we compared the effects of our hypnotic analgesia condition with that of a cluster of our cognitive-behavioral and placebo-control conditions. After controlling for baseline intensity, postintensity was predicted by Openness and the interaction of condition and Openness. This suggests that the effect of the hypnotic condition was moderated by Openness to Experience.
Table 1 Simultaneous regressions testing moderation of effects of treatment condition by Openness to Experience. Comparison and predictor
F
p<
Beta
Eta2
Hypnotic vs. cognitive-behavioral and placebo Baseline intensity 486.97 Openness to Experience (O) 13.41 Treatment condition (TC) 1.25 TC O 4.24
.001 .001 .265 .040
.70 .05 .23 .43
.52 .03 .00 .01
Hypnotic vs. cognitive-behavioral Baseline intensity Openness to Experience (O) Treatment condition (TC) TC O
334.03 8.03 4.00 4.48
.001 .005 .046 .035
.71 .03 .50 .54
.52 .03 .01 .01
Hypnotic vs. placebo Baseline intensity Openness to Experience (O) Treatment condition (TC) TC O
365.07 10.80 0.10 3.32
.001 .001 .750 .069
.67 .05 .07 .42
.53 .03 .20 .01
Fig. 1. Interaction of Openness to Experience and treatment condition on residualized pain intensity change scores.
In the second regression, we compared the effects of our hypnotic analgesia condition with that of our cognitive-behavioral condition. After controlling for baseline intensity, postintensity was predicted by Openness, condition, and the interaction of condition and Openness. Once again, this suggests that the hypnotic condition was moderated by Openness to Experience. In the third regression, we compared the effects of our hypnotic analgesia condition with our placebo-control condition. After controlling for baseline intensity, postintensity was predicted only by the main effect of Openness. However, the interaction of condition and Openness approached significance (p = .069). Fig. 1 summarizes the interaction of Openness and treatment condition in the three regressions. Residualized change scores in pain intensity were generated by regressing postintensity on baseline intensity. A scatterplot of residualized change scores and Openness was created, and a regression line was generated for each of the three conditions. Fig. 1 shows that higher levels of Openness were associated with more pain reduction in the hypnotic analgesia condition than in the cognitive-behavioral and placebo-control conditions. Figs. S1, S2, and S3 in the Supplementary materials show the scatterplots of Openness and residualized change scores, as well as the regression lines for the hypnotic analgesia, cognitivebehavioral, and placebo-control conditions respectively. The NEO PI-R Openness to Experience scale is composed of six facet subscales: Openness to Fantasy, Aesthetics, Feelings, Actions, Ideas, and Values. When the three simultaneous regressions were repeated substituting each of the facet scores in turn for the overall Openness score, only the Openness to Aesthetics facet subscale showed a significant interaction with treatment condition in predicting pain reduction. Table S2 in the Supplementary materials shows the results of the three regressions for the Openness to Aesthetics facet subscale.
4. Discussion We found a clear relationship between Openness to Experience and responding to hypnosis. Specifically, Openness moderated the effect of our hypnotic analgesia suggestion. The relationship between Openness and pain reduction was stronger in our hypnotic analgesia condition than in our cognitive-behavioral and placebocontrol conditions. This moderator effect appears to have been carried primarily by the Openness to Aesthetics facet.
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In contrast, past research has reported weak (Glisky et al., 1991; Nordenstrom et al., 2002) or nonexistent (Glisky & Kihlstrom, 1993; Green, 2004; Malinoski & Lynn, 1999; Radtke & Stam, 1991) relations between Openness and hypnotic suggestibility. Why were we able to demonstrate a relationship between Openness and hypnotic pain reduction when past research has generally failed to show clear associations between Openness and hypnotic suggestibility? Perhaps our use of an experimental manipulation and moderator analysis made it easier to identify a relationship than the correlational approach employed in past research. Another possible explanation involves the difference between our hypnotic analgesia suggestion and kind of suggestions typically comprising hypnotic suggestibility scales. There are three types of hypnotic suggestions. In an ideomotor suggestion, the person is invited to experience a motor movement. In a challenge suggestion, the person is told he or she will not be able to perform a particular behavior and then is asked to carry out the prohibited action. In a cognitive suggestion, the person is invited to experience an alteration in cognitive functioning. Thus, ideomotor and most challenge suggestions tend to focus on the performance or inhibition of a motor movement. Cognitive suggestions focus more on alterations in sensations, perceptions, thoughts, and feelings. Our hypnotic analgesia suggestion (i.e., ‘‘your hand is becoming more and more numb. . . more and more insensitive. . . as if it were covered in a thick, thick glove. . . you may not be able to feel anything at all through that glove on your hand. . .’’) is an example of a cognitive suggestion. Of note, standardized hypnotic suggestibility scales typically consist of a mix of ideomotor, challenge, and cognitive test suggestions. Perhaps we were able to identify a clear association between Openness and hypnotic responding because the content of some of the items on the NEO PI-R Openness to Aesthetics scale (e.g., ‘‘Sometimes when I am reading poetry or looking at a work of art, I feel a chill or wave of excitement‘‘) is similar to the experience of cognitive suggestions like hypnotic analgesia. In contrast, items on the Openness to Aesthetics scale seem less similar to the experience of ideomotor and challenge suggestions, which comprise the majority of test suggestions on standardized suggestibility scales. Indeed, the measure of hypnotic suggestibility (i.e., the Harvard Group Scale of Hypnotic Susceptibility) used in all past research in this area is composed almost exclusively of ideomotor and challenge suggestions. Demonstrating that Openness to Experience moderated the effect of our hypnotic treatment has important theoretical implications. This is the first study to clearly place individual differences in hypnotic behavior within the sphere of one of the Big Five factors. Most individual differences variables are embedded in a rich network of constructs. In contrast, hypnosis has been characterized as a field lacking a nomological network (Nadon, 1997). Showing that Openness was more strongly related to the effect of our hypnotic analgesia condition than to that of our non-hypnotic conditions suggests that hypnotic responding may be subsumed within the nomological net of Openness to Experience. Our results may also have useful clinical implications. Pain patients scoring high on Openness to Experience might be good candidates for hypnotic pain interventions. It is sometimes recommended that hypnotic suggestibility be assessed when hypnosis is considered as a treatment. However, administering a standardized measure of hypnotic suggestibility can be timeconsuming and requires the services of a professional who is skilled in hypnosis. Alternatively, Openness can assessed in a relatively brief period of time using standardized paper and pencil measures that do not require the presence of a professional hypnotist. Future research might beneficially explore whether Openness moderates the effect of hypnosis on clinical pain.
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Some limitations of this study should be noted. First, participants completed the NEO PI-R after they were administered the pain interventions. It is possible that among participants assigned to the hypnotic analgesia condition, the experience of the analgesia suggestion affected subsequent responses on the NEO PI-R, thereby accounting for the moderator effect. Second, our sample overrepresented females and young people relative to their numbers in the general population. Finally, compared with clinical pain, the experimental pain stimulus used in this study was relatively mild and had no health implications. In sum, we found that our hypnotic analgesia condition was moderated by Openness to Experience. The relationship between Openness and pain reduction was stronger in our hypnotic analgesia condition than in the non-hypnotic conditions. Our study is the first to clearly place individual differences in hypnotic pain reduction, and by extension, individual differences in hypnotic responding, within the broad domain of the Openness to Experience factor of the Five Factor Personality Model. A logical progression in this line of inquiry would involve exploring interrelationships of Openness to Experience, absorption, fantasy-proneness, hypnotic suggestibility, and responding to suggestions for hypnotic analgesia. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jrp.2012.10.006. References Baron, R. M., & Kenny, D. A. (1986). The moderator-mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations. Journal of Personality and Social Psychology, 51, 1173–1182. Costa, P. T., & McRae, R. R. (1992). Revised NEO Personality Inventory (NEO PI-R) and Neo Five-Factor Inventory (NEO-FFI) Professional Manual. Odessa, FL: Psychological Assessment Resources. de Groh, M. (1989). Correlates of hypnotic susceptibility. In N. P. Spanos & J. F. Chaves (Eds.), Hypnosis: The Cognitive-Behavioral Perspective (pp. 32–63). Amherst, NY: Prometheus Books. Forgione, A. G., & Barber, T. X. (1971). A strain-gauge pain stimulator. Psychophysiology, 8, 102–106. Glisky, M. L., & Kihlstrom, J. F. (1993). Hypnotizability and facets of openness. International Journal of Clinical and Experimental Hypnosis, 41, 112–123. Glisky, M. L., Tataryn, D. J., Tobias, B. A., Kihlstrom, J. F., & McConkey, K. M. (1991). Absorption, openness to experience, and hypnotizability. Journal of Personality and Social Psychology, 60, 263–272. Green, J. P. (2004). The five factor model of personality and hypnotizability. Little variance in common. Contemporary Hypnosis, 21, 161–168. Gwynn, M. I., & Spanos, N. P. (1996). Hypnotic responsiveness, nonhypnotic suggestibility, and responsiveness to social influence. In R. G. Kunzendorf, N. P. Spanos, & B. Wallace (Eds.), Hypnosis and Imagination (pp. 147–175). Amityville, NY: Baywood Publishing. Lynn, S. J., & Rhue, J. W. (1986). The fantasy-prone person: Hypnosis, imagination, and creativity. Journal of Personality and Social Psychology, 51, 404–408. Malinoski, P. T., & Lynn, S. J. (1999). The plasticity of early memory reports: Social pressure, hypnotizability, compliance and interrogative suggestibility. International Journal of Clinical and Experimental Hypnosis, 47, 320–345. Milling, L. S., Reardon, J. M., & Carosella, G. M. (2006). Mediation and moderation of psychological pain treatments: Response expectancies and hypnotic suggestibility. Journal of Consulting and Clinical Psychology, 74, 253–262. Montgomery, G. H., DuHamel, K. N., & Redd, W. H. (2000). A meta-analysis of hypnotically induced analgesia: How effective is hypnosis? International Journal of Clinical and Experimental Hypnosis, 48, 138–153. Nadon, R. (1997). What this field needs is a good nomological network. International Journal of Clinical and Experimental Hypnosis, 45, 314–323. Nordenstrom, B. K., Council, J. R., & Meier, B. P. (2002). The ‘Big Five’ and hypnotic suggestibility. International Journal of Clinical and Experimental Hypnosis, 50, 276–281. Radtke, H. L., & Stam, H. J. (1991). The relationship between absorption, openness to experience, anhedonia, and susceptibility. International Journal of Clinical and Experimental Hypnosis, 39, 39–56. Tellegen, A., & Atkinson, G. (1974). Openness to absorbing and self-altering experiences (‘‘absorption’’), a trait related to hypnotic susceptibility. Journal of Abnormal Psychology, 83, 268–277. Zamansky, H. S., Scharf, B., & Brightbill, R. (1964). The effect of expectancy for hypnosis on prehypnotic performance. Journal of Personality, 32, 236–248.