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Suppressing unwanted memories: where there is a will, there is a way?
Behaviour Research and Therapy 41 (2003) 727–736 www.elsevier.com/locate/brat
Shorter communication
Suppressing unwanted memories: where there is a will, there is a way? E. Rassin a,∗, A. van Brakel b, E. Diederen b a
Erasmus University Rotterdam, Faculty of Social Sciences, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands b Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands Received 10 July 2002; received in revised form 20 January 2003; accepted 3 February 2003
Abstract Research suggests that suppressing unwanted thoughts, generally, is an ineffective thought control strategy, because suppression attempts oftentimes fail, and, furthermore, result in a paradoxical increase of unwanted thoughts, later on. The present study sought to investigate whether manipulated expectations about suppression efficacy determine actual effects of suppression attempts. To test this hypothesis, participants listened to an audiotaped story, and were subsequently appointed to one of four conditions: a noinstruction-control (n = 20), suppression (n = 20), suppression-works (n = 20; participants were told that suppression generally is a fruitful strategy), or suppression-does-not-work (n = 25; participants were told that suppression primarily has paradoxical effects) condition. Two hours later, participants’ memories of the story were tested, and several metamemory questions were answered. Induced expectations actually determined the perceived efficacy of suppression attempts, as well as thought frequency, although perceived or actual accuracy of recollections was not affected by the instructions. 2003 Elsevier Science Ltd. All rights reserved. Keywords: Memory; Metacognition; Thought suppression
1. Introduction In 1987, Wegner, Schneider, Carter, and White introduced the thought suppression paradigm, in which the participant is instructed to try not to think of a discrete thought (e.g., a white bear) for a 5-min period. Wegner et al. found that in spite of their suppression attempts, participants reported to have thought seven times of white bears. Furthermore, suppression seemed to result ∗
Corresponding author. E-mail address: [email protected] (E. Rassin).
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in a rebound of target thoughts, when suppression instructions no longer applied. Hence, these results suggest that people are unable to suppress a target thought, and moreover suppression seems to be a counterproductive strategy. The paradoxical effect of thought suppression has been considered to be an etiological factor in the development of intrusion-based psychiatric syndromes, such as obsessive-compulsive disorder (OCD; see Wegner, 1989). Notwithstanding the thought suppression paradigm’s relevance for theories of obsession, its implications do not by definition apply to conditions in which intrusive thoughts other than obsessions are crucial (e.g., traumatic memories as occurring in post traumatic stress disorder [PTSD]; American Psychiatric Association, 1994). It is likely that suppression of a single word (e.g., white bear), an obsessional fantasy about jumping before a train, or the memory of a traumatic incident all require different mental operations. For example, one difference is that compared to other target thoughts, a recollection is more elaborated, because it pertains to at least several minutes of an experienced event. In their meta-analysis of suppression experiments, Abramowitz, Tolin and Street (2001) found evidence to suggest that suppression efficacy and target elaborateness are negatively related. In their words: “larger rebound effects were found with nondiscrete target thoughts (e.g., a story) than with discrete thoughts (e.g., a white bear)” (p. 700). In 1996, Wegner, Quillian, and Houston modified the original Wegner, Schneider, Carter and White (1987) thought suppression paradigm in order to make it more suitable as a model of real life situations in which recollections are the target of suppression attempts. These authors showed their participants a film clip and subsequently divided them into suppression, expression, and control groups. Participants had to carry out their instructions for 5 h and then returned to the lab, where their memory of the film was tested. Findings suggested that suppression resulted in a perceived fragmentation of memory (i.e., snapshot likeness). Furthermore, suppression participants performed less well on questions pertaining to the chronology of the film. Based on these findings, Wegner, Quillian and Houston (1996) concluded that suppression has a partial memory undermining potential. In their words: “The snapshot effect of suppression suggests that people might indeed do something that resembles the effect attributed to classical repression” (p. 689). This implies that, contrary to the results of the bulk of thought suppression studies pertaining to discrete thoughts (e.g., white bears), suppression of autobiographical recollections seemed to be partly successful. It is important to note that this differential finding may have to do with the employed dependent variables. Whereas in the original thought suppression study (Wegner et al., 1987), target thought frequency (i.e., intrusive memory) was the main variable, the Wegner et al. (1996) experiment (also) addressed participants’ recollection of the content of the target thought (i.e., explicit memory). To date, a handful of studies has built on the Wegner et al. (1996) work. Rassin (2001) used an audiotaped story as to be suppressed stimulus and found results similar to those reported by Wegner et al. (1996). Rassin, Merckelbach and Muris (1997), however, found that suppressing thoughts of an emotional film clip did not result in a decline of memory. On the contrary, these authors reported that suppression resulted in a paradoxical increase of film-related thoughts, and furthermore in an increased perceived clarity of memory. The conflicting findings may be explained in terms of the employed stimuli. Whereas the Wegner et al. (1996) and the Rassin (2001) study relied on neutral stimuli (a film clip about a union strike, and a written story about a vacation in Spain, respectively), Rassin et al. (1997) used an emotional film (an amateur film of a tourist being attacked by a grizzly bear). Perhaps then, suppression has some desired (i.e.,
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memory undermining) effects in case of neutral memories, but not with emotional recollections. Davies and Clark (1998), as well as Harvey and Bryant (1998) employed the Wegner et al. (1996) paradigm, although these authors were not interested in the effects of suppression on memory, but merely in suppression effects on thought frequency. Davies and Clark (1998) found that suppressing thoughts of an emotional film clip resulted in a rebound of film-related thoughts, while such an effect was absent in case of a neutral film. Interestingly, Harvey and Bryant (1998) reported that suppression resulted in a thought rebound, regardless of whether participants saw a neutral, pleasant, or aversive film clip. These divergent findings across studies may imply that other factors are involved in the determination of suppression efficacy. One such factor may be individual differences in the ability to suppress unwanted thoughts. To date, little is known about the factors that determine which individuals are successful suppressors (see Bowers & Woody, 1996; Kelly & Nauta, 1997; Rutledge, Hancock, & Rutledge, 1996; Rutledge, Hollenberg, & Hancock, 1993). It has been argued that the precise technique use to suppress target thoughts may determine suppression efficacy (Wegner et al., 1987; Wells & Davies, 1994). For example, individuals may suppress a target thought by means environmental distraction, cognitive distraction (e.g., concentrating on recent worries), or mental or physical selfpunishment. Wegner (1994) argued that people might become successful suppressors through practice, but this hypothesis has not yet been tested. Brewin and Beaton (2002) argue that fluid intelligence contributes to the ability to successfully suppress unwanted thoughts. The present study set out to explore the effect of prior expectations on the efficacy of attempts to suppress autobiographical recollections. More specifically, it was tested whether the prior idea that suppression can be successful, actually results in successful suppression. It could be argued that a strong belief in the efficacy of suppression may foster the perception of suppression as a fruitful strategy. In other words, people who are convinced that it is possible to suppress a recollection may actually be better at suppressing recollections (cf. a self-fulfilling prophecy effect). Results from a study by Crombag and Van Koppen (1994) suggest that a vast majority (i.e., 90%) of the respondents (268 healthy volunteers) believes in the possibility of successful suppression. Approximately 50% of these respondents were so convinced of suppression efficacy that they were open to the possibility that they themselves had experienced extremely traumatic events in the past of which they no longer had recollections, due to suppression. The present study sought to explore whether prior expectations about suppression efficacy influence the actual effects of suppression in an experimental set-up.
2. Method 2.1. Participants Eighty-five undergraduate students (69 women) participated in the experiment. Mean age in the sample was 20.60 years (SD = 2.26 years; range: 18–31). Participants were randomly assigned to one of four conditions: a no-instruction-control condition (n = 20), a suppression (per se) condition (n = 20), a “suppression-works” condition (n = 20), or a “suppression-does-not-work” condition (n = 25). There were no age (F[3] ⬍ 1.0) or sex (χ2[3, N = 85] = 4.77, p = 0.19)
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differences between the four groups. Participants were tested individually, and received a small financial compensation. 2.2. Procedure Upon arrival at the laboratory, an audiotaped story was played to the participant (see below). He/she was instructed to identify with the main character in the story. After this, participants were randomly assigned to the control, suppression, suppression-works, or suppression-does-notwork condition. Participants in the no-instruction-control condition were instructed as follows: “During the next two hours you are free to think about anything you want to. You may think of the story, or of anything else. In two hours, you must return to the laboratory in order to complete several questionnaires. The second session will take approximately half an hour”. Participants in the suppression condition received the following written instruction: “During the next two hours you are free to think about anything you want to. However, there is one exception: you must try not to think about the story. If thoughts about the story come into consciousness, you should use any means necessary to make them go away. What you should do, is comparable to what you might be tempted to do if you found out bad news just before an exam. You would try to push that bad news out of your mind during the exam. That is exactly what I would like you to do with every thought of the story—if any—for the next two hours. In two hours, you must return to the laboratory in order to complete several questionnaires. The second session will take approximately half an hour”. Participants in the suppression-works condition received the following additional instruction: “In daily life, people often claim to have suppressed certain memories. Recent studies indicate that it is, indeed, possible to suppress recollections to the point that one cannot remember them. This memory undermining effect has been observed after no more than a few hours. The present study seeks to further investigate the effects of suppression on memory”. Participants in the suppression-does-not-work condition received the following additional instruction: “In daily life, people often claim to have suppressed certain memories. Recent studies indicate, however, that it is impossible to suppress recollections. Moreover, if one tries to suppress a certain recollection, that recollection will come to mind more often. In fact, trying to suppress information is a very good way to remember it well. This effect of improved memory due to suppression attempts has been observed after no more than a few hours. The present study seeks to further investigate the effects of suppression on memory”. Before leaving the lab, participants answered two questions concerning the emotional valence of the story, and their identification with the main character. In the second session, participants were first asked to complete a short questionnaire that was constructed for this study (see below). After this, they had to recall the story as literally as possible. This free recall task was carried out in writing. Following the free recall, participants were asked two final questions (see below). 2.3. Materials The story that was used as stimulus was derived from the work of Wenzlaff, Wegner and Roper (1988). This story is about a person who is late for an important job interview. On his way, he
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speeds and passes a red traffic light. A severe accident in which his car crashes with another is the result. The story ends with a description of the driver of the other car who has a dead infant in her arms. Immediately after the story had been played to the participants, they were asked to rate its unpleasantness on a visual analogue scale (VAS; 0 = not at all unpleasant; 100 very unpleasant). The mean score on this VAS was 67.32 (SD = 24.75) indicating that the story was judged to be fairly unpleasant. Participants were also asked to report the extent to which they could identify with the main character in the story (0 = not at all; 100 = completely). The questionnaire that was constructed for this study consisted of 13 items. The first question (“How many times did you think of the story, during the past two hours?”) pertained to the number of story-related intrusions. Second, the respondent was asked to what extent he/she had tried to engage in suppression. This item, as were all the following, was answered on a VAS (0 = not at all; 100 = very strongly). The third item pertained to the perceived efficacy of suppression attempts (0 = not at all successful; 100 = very successful). The next item asked how accurate participants estimated their own memory of the story (0 = not at all accurate; 100 = very accurate). The following four items pertained to the perceived clarity of participants’ memories (i.e., clarity, detailedness, liveliness, and intensity). These four items were clustered into a mean overall metamemory variable (range: 0–100; Cronbach’s alpha = 0.87), with higher scores indicating that the participant experienced his memory as clearer (these items were adopted from Johnson, Foley, Suengas, & Raye, 1988). Based on the Wegner et al. (1996) findings, the next three items specifically pertained to sequence memory. Participants were asked whether the chronology of the story was still clear to them, whether they thought of the story as a collection of snapshots or as a fluent whole, and whether they, now, tended to think of the whole story or rather only of specific parts of it. These three items were conjoined into one snapshot likeness variable (range: 0–100; a = 0.46), with higher scores indicating perceived snapshot likeness. Lastly, participants were asked the same two questions which they had answered in the morning session, that is, they had to rate the unpleasantness of the story, as well as the extent to which they, now, were able to identify with the main character in the story. As to the scoring of the free recall, the number of correctly recalled propositions was counted (this was done, blind to condition, by the third author). The maximal score on this variable was set at 79 units. As mentioned before, participants answered two final questions after the free recall task. First, they had to indicate how much effort the free recall task had taken. This question was answered on a VAS ranging from 0 (very little) to 100 (very much). The last question asked what the effect of suppression on memory is according to the respondent. This item had a multiple choice answer format with the following three categories: 1) The story is forgotten more rapidly, 2) The story remains better remembered, and 3) Do not know. 3. Results Table 1 presents the mean scores for the control, suppression, suppression-works, and suppression-does-not-work groups on the various variables. As can be seen in this table, several group differences (i.e., thought frequency, suppression effort, perceived suppression efficacy, and
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Table 1 Mean scores (and standard deviations) for the control, suppression, suppression-works, and suppression-does-not-work group on the various variables
Thought-frequency Efforts to suppress Success of suppression Estimated memory accuracy Metamemory (clarity) Snapshot likeness Unpleasantness of the story a Identification with main character a Correctly reproduced details Perceived difficulty of free recall
Control
Suppression
Suppression works
Suppression F(3) does not work
p
3.20 (2.38) 10.55 (12.40) 62.12 (29.49) 71.79 (15.02) 62.75 (20.06) 38.91 (17.77) 53.68 (26.05) 58.11 (24.65)
3.50 (2.26) 64.75 (21.89) 69.00 (26.54) 70.25 (14.55) 64.59 (11.17) 48.48 (17.73) 51.95 (19.80) 44.70 (23.91)
2.90 (1.92) 50.80 (25.05) 79.80 (13.86) 76.95 (15.81) 58.10 (17.64) 45.38 (18.39) 38.30 (19.55) 41.95 (21.97)
6.32 (4.03) 53.52 (24.01) 59.58 (23.00) 68.32 (16.65) 59.50 (15.84) 52.05 (13.70) 57.04 (20.50) 54.28 (22.05)
7.14 ⬍ 0.01 24.31 ⬍ 0.01 3.02 0.04 1.20 0.31 ⬍ 1.00 2.32 0.08 3.08 0.03 2.23 0.09
31.20 (6.23) 32.05 (23.12)
30.50 (6.21) 34.85 (21.97)
30.90 (6.78) 26.95 (20.34)
31.96 (7.12) 29.92 (22.13)
⬍ 1.00 ⬍ 1.00
a Scores displayed in this table were obtained during the second session, although these questions were also asked during the first session, immediately after the story.
unpleasantness ratings) reached significance (a was set at 0.05) in the analyses of variance (ANOVAs). Post hoc analyses (Tukey honestly significant difference) revealed that, with respect to thought frequency, the suppression-does-not-work group scored higher than the other three groups. The difference in suppression effort scores was due to the low score in the control condition. As to perceived suppression efficacy, as well as perceived unpleasantness, the differences were located between the suppression-works and suppression-does-not-work groups. Mean scores of the unpleasantness ratings obtained immediately after the story were 71.05 (SD = 24.09), 61.50 (SD = 25.27), 72.35 (SD = 20.95), and 75.08 (SD = 20.95) for the control, suppression, suppression-works, and suppression-does-not-work group, respectively (F[3] = 1.42, p = 0.24). These scores were analyzed together with the corresponding scores obtained during the second session (see Table 1) in a 4 (groups) x 2 (times) ANOVA with repeated measures on the last factor. Results yielded a main effect of time (F[1] = 59.49, p ⬍ 0.01), and an interaction effect (F[3,82] = 4.12, p = 0.01), but no group effect (F[3] = 1.51, p = 0.22). As to identification with the main character, immediately after having heard the story, control participants scored 66.50 (SD = 23.78), suppression 54.45 (SD = 27.80), suppression-works 60.85 (SD = 21.86), and suppression-does-not-work 67.32 (SD = 21.92): F(3) = 1.32, p = 0.27. Again, these scores were, together with corresponding second time scores, analyzed by means of ANOVA, which yielded a main effect of time (F[1] = 28.82, p ⬍ 0.01), but no group (F[3] = 1.82, p = 0.15), or interaction effect (F[3,82] = 1.21, p = 0.31). The last item pertained to the expected consequences of suppression. Chi-square analysis revealed that participants in the control condition were more strongly convinced that suppression results in a declination of memory than were participants in the three suppression conditions. Suppression-does-not-work instructions seemed to have the most extreme influence, in that none of the participants in this condition reported to believe that suppression has a memory undermining
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effect. This difference was statistically significant: χ2(6, N = 85) = 28.01, p ⬍ 0.01. The frequency of endorsed answers is presented in Table 2. 4. Discussion The main purpose of this study was to investigate the influence of expectations about suppression on the actual efficacy of attempts to suppress recollections. More specifically, it was hypothesized that people who are convinced of the possibility of successful suppression will do better in an experimental set-up in which a recollection of an elaborated stimulus is to be suppressed. What do our findings tell us with respect to this hypothesis? First, given that participants in the three suppression conditions reported equal effort to engage in suppression attempts, it seems that participants who had received the suppression-works instruction actually experienced their suppression attempts as more fruitful than those who had been told that suppression generally does not work. Apparently, the explicit instructions sufficed to create certain expectations, which led participants to perceive their suppression efforts in a concordant manner. Second, the suppression-does-not-work instruction seemed to have resulted in an increased frequency of storyrelated thoughts, while such an increase was not found in the suppression or suppression-works conditions. Third, compared to no-instruction-control, suppression (per se, with positive, or negative instruction) seemed to have no effect on perceived (i.e., estimated accuracy, metamemory, snapshot likeness, and recall difficulty) or actual (i.e., free recall) memory, although the nonsignificant trend (p = 0.08) of suppression participants perceiving their recollections as more snapshot like than did controls, is reminiscent of the findings reported by Wegner et al. (1996). Fourth, the prior expectation that suppression works resulted in decreased unpleasantness ratings after suppression, compared to the expectation that suppression does not work. In summary, our findings suggest that prior expectations about suppression efficacy actually determine perceived suppression efficacy, in an experimental set-up. This self-fulfilling prophecy effect was not limited to perceived efficacy, but also affected the frequency of stimulus-related thoughts, as well as the emotional impact of the stimulus. The induced expectations had no influence on the quality of participants’ explicit recollection of the stimulus material. Given their effect on target thought frequency estimates, prior expectations may explain some of the contradictory Table 2 Number of participants endorsing answers describing expected consequences of suppression in the control, suppression, suppression-works, and suppression-does-not-work Group (N = 85)
Rapid decline of memory Memory improvement Do not know
Control
Suppression
Suppression works
Suppression does not work
11 (55%) 6 (30%) 3 (15%)
4 (20%) 13 (65%) 3 (15%)
6 (30%) 11 (55%) 3 (15%)
0 (0%) 24 (96%) 1 (4%)
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findings obtained in thought suppression research to date. Whereas some researchers found that thought suppression instructions result in immediate and rebound increases of target thought frequency, others failed to find such paradoxical effects (see, for reviews, Abramowitz et al., 2001; Purdon, 1999). Perhaps, part of this contradiction is due to individual differences in the (expectation-driven) capability to suppress target thoughts at will. Contrary to our hypothesis, participants who were convinced of the efficacy of suppression were not found to have poorer explicit memory than participants who were not convinced of suppression efficacy. Apparently, it is possible for people to think of their suppression attempts as successful, without developing poorer recollection of the suppressed information. Perhaps then, participants have evaluated the efficacy of their suppression attempts by using the number of stimulus-related thoughts as criteria, while leaving other possible parameters (such as clarity and estimated accuracy of their recollection) out of the equation. Whereas our results suggest that metacognitions about suppression can diverge from actual accuracy of recollections (see, for comparable divergences, Belli, Winkielman, Read, Schwarz, & Lynn, 1998; Kindt & Van den Hout, in press), Christianson and Bylin (1999) found that metacognition can actually affect memory. These authors instructed their participants to read a story about a murder, and subsequently asked them several questions (including a free recall assignment). After one week, participants, again, had to answer questions pertaining to the story. All participants had to identify with the perpetrator in the story. Half of the participants were instructed to simulate amnesia for the story content, as if they wanted to evade legal responsibility for the crime. This instruction applied to the first interview, while during the second questioning, after one week, all participants had to answer the questions to the best of their knowledge. It seemed that participants who had feigned amnesia during the first interview, recalled fewer details after one week. Hence, simulated amnesia had resulted in actual amnesia. These findings suggest that amnesia may be rooted in cognitive operations that involve metacognitions about memory and amnesia. However, the instructions given to participants in the Christianson and Bylin (1999) study were explicitly directed at amnesia, while our study focused on suppression, leaving the goal of suppression attempts (i.e., absence of intrusions, memory loss, or both) unsaid. Although suppression did not affect explicit memory, results suggest that suppression-works instructions decreased the emotional impact of the recollection. This is in line with Walker, Vogl, and Thompson’s (1997) finding that people tend to minimize the emotional impact of unpleasant memories. Walker, Vogl and Thompson (1997) argue that the reduction of emotional valence is in contradiction with the old Freudian idea of suppression, because their results indicate that people tend to decrease the emotional aspect of unpleasant events, while remembering these events well, whereas Freud claimed that the memory itself becomes inaccessible due to suppression. Evidently, our findings are more in favour of the mechanism proposed by Walker et al. (1997). The main limitation of the present study lies in the circumstance that it is a laboratory model of real-life situations in which people want to suppress memories of traumatic experiences. It seems likely that in real life people are more motivated to get rid of traumatic memories than were the participants in our experiment. Therefore, it might be expected that the influence of expectations on suppression efficacy is more pronounced in real life. Another limitation is the possibility that experimental demand has accounted for a part of the results. However, if experimental demand effects are responsible for the observed group differences, it remains unclear why participants indulged some variables (e.g., thought frequency, perceived suppression efficacy, and
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unpleasantness ratings), but not others (e.g., estimated memory accuracy, metamemory, the free recall task, and perceived difficulty of the free recall task). Although thought frequency and perceived suppression efficacy are obvious variables to be affected by experimental demand, the unpleasantness rating is less so. As to the clinical implications, the current findings contradict the bulk of the suppression research that highlights the inefficacy of suppression attempts (see Abramowitz et al., 2001; Purdon, 1999). Our findings suggest that individuals who are sincerely convinced of suppression efficacy appear to be somewhat successful in their suppression attempts, in that they report experiencing few intrusions. Furthermore suppression appears to alleviate discomfort in the sense that the emotional impact of the suppressed recollection is reduced. To sum up, our study sought to elucidate whether expectations about suppression efficacy determine actual efficacy in an experimental set-up. The data give rise to the following conclusions. First, it seems that expectations regarding suppression efficacy could be manipulated relatively easily (i.e., by means of a short written instruction). Second, induced expectations determined perceived suppression efficacy. More specifically, participants who were told that successful suppression is possible, experienced their suppression efforts as more effective, reported to experience fewer intrusions, and evaluated the stimulus as less aversive, compared to participants who were told that suppression is a counterproductive strategy. The induced expectations did not seem to extend to perceived or actual accuracy of recollections. Third, our findings suggest that, compared to no-instruction-control, suppression had little or no effect on explicit memory. Acknowledgements The first author received a grant from NWO to complete this study. References Abramowitz, J. S., Tolin, D. F., & Street, G. P. (2001). Paradoxical effects of thought suppression: A meta-analysis of controlled studies. Clinical Psychology Review, 21, 683–703. American Psychiatric Association (APA) (1994). Diagnostic and statistical manual for mental disorders. (4th ed.) (DSM IV). Washington: APA. Belli, R. F., Winkielman, P., Read, J. D., Schwarz, N., & Lynn, S. J. (1998). Recalling more childhood events leads to judgments of poorer memory: Implications for the recovered/false memory debate. Psychonomic Bulletin & Review, 5, 318–323. Bowers, K. S., & Woody, E. Z. (1996). Hypnotic amnesia and the paradox of intentional forgetting. Journal of Abnormal Psychology, 105, 381–390. Brewin, C. R., & Beaton, A. (2002). Thought suppression, intelligence, and working memory capacity. Behaviour Research and Therapy, 40, 923–930. Christianson, S., & Bylin, S. (1999). Does simulating amnesia mediate genuine forgetting for a crime event? Applied Cognitive Psychology, 13, 495–511. Crombag, H., & Van Koppen, P. (1994). Verdringen als sociaal verschijnsel [Repression as a social phenomenon]. De Psycholoog, 29, 409–415 in Dutch. Davies, M. I., & Clark, D. M. (1998). Thought suppression produces a rebound effect with analogue post-traumatic intrusions. Behaviour Research and Therapy, 36, 571–582.
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Harvey, A. G., & Bryant, R. A. (1998). The role of valence in attempted thought suppression. Behaviour Research and Therapy, 36, 757–763. Johnson, M. K., Foley, M. A., Suengas, A. G., & Raye, C. L. (1988). Phenomenal characteristics of memories for perceived and imagined autobiographical events. Journal of Experimental Psychology: General, 117, 371–376. Kelly, A. E., & Nauta, M. M. (1997). Reactance and thought suppression. Personality and Social Psychology Bulletin, 23, 1123–1132. Kindt, M., & Van den Hout, M. (2003). Dissociation and memory fragmentation: Experimental effects on meta-memory but not on actual memory performance. Behaviour Research and Therapy, Purdon, C. (1999). Thought suppression and psychopathology. Behaviour Research and Therapy, 37, 1029–1054. Rassin, E. (2001). Thought suppression, memory, and interrogative suggestibility. Psychology, Crime & Law, 7, 45–55. Rassin, E., Merckelbach, H., & Muris, P. (1997). Effects of thought suppression on episodic memory. Behaviour Research and Therapy, 35, 1035–1038. Rutledge, P. C., Hancock, R. A., & Rutledge, J. H. (1996). Predictors of thought rebound. Behaviour Research and Therapy, 34, 555–562. Rutledge, P. C., Hollenberg, D., & Hancock, R. A. (1993). Individual differences in the Wegner rebound effect: Evidence for a moderator variable in thought rebound following thought suppression. Psychological Reports, 72, 867–880. Walker, W. R., Vogl, R. J., & Thompson, C. P. (1997). Autobiographical memory: Unpleasantness fades faster than pleasantness over time. Applied Cognitive Psychology, 11, 399–413. Wegner, D. M. (1989). White bears and other unwanted thoughts: Suppression, obsession, and the psychology of mental control. London: The Guilford Press. Wegner, D. M. (1994). Ironic processes of mental control. Psychological Review, 101, 34–52. Wegner, D. M., Quillian, F., & Houston, C. (1996). Memories out of order: Thought suppression and the disassembly of remembered experience. Journal of Personality and Social Psychology, 71, 680–691. Wegner, D. M., Schneider, D. J., Carter, S. R., & White, T. L. (1987). Paradoxical effects of thought suppression. Journal of Personality and Social Psychology, 53, 5–13. Wells, A., & Davies, M. I. (1994). The thought control questionnaire: A measure of individual differences in the control of unwanted thoughts. Behaviour Research and Therapy, 32, 871–878. Wenzlaff, R. M., Wegner, D. M., & Roper, D. (1988). Depression and mental control: The resurgence of unwanted negative thoughts. Journal of Personality and Social Psychology, 55, 882–892.
Shorter communication
Suppressing unwanted memories: where there is a will, there is a way? E. Rassin a,∗, A. van Brakel b, E. Diederen b a
Erasmus University Rotterdam, Faculty of Social Sciences, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands b Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands Received 10 July 2002; received in revised form 20 January 2003; accepted 3 February 2003
Abstract Research suggests that suppressing unwanted thoughts, generally, is an ineffective thought control strategy, because suppression attempts oftentimes fail, and, furthermore, result in a paradoxical increase of unwanted thoughts, later on. The present study sought to investigate whether manipulated expectations about suppression efficacy determine actual effects of suppression attempts. To test this hypothesis, participants listened to an audiotaped story, and were subsequently appointed to one of four conditions: a noinstruction-control (n = 20), suppression (n = 20), suppression-works (n = 20; participants were told that suppression generally is a fruitful strategy), or suppression-does-not-work (n = 25; participants were told that suppression primarily has paradoxical effects) condition. Two hours later, participants’ memories of the story were tested, and several metamemory questions were answered. Induced expectations actually determined the perceived efficacy of suppression attempts, as well as thought frequency, although perceived or actual accuracy of recollections was not affected by the instructions. 2003 Elsevier Science Ltd. All rights reserved. Keywords: Memory; Metacognition; Thought suppression
1. Introduction In 1987, Wegner, Schneider, Carter, and White introduced the thought suppression paradigm, in which the participant is instructed to try not to think of a discrete thought (e.g., a white bear) for a 5-min period. Wegner et al. found that in spite of their suppression attempts, participants reported to have thought seven times of white bears. Furthermore, suppression seemed to result ∗
Corresponding author. E-mail address: [email protected] (E. Rassin).
0005-7967/03/$ - see front matter 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0005-7967(03)00035-4
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in a rebound of target thoughts, when suppression instructions no longer applied. Hence, these results suggest that people are unable to suppress a target thought, and moreover suppression seems to be a counterproductive strategy. The paradoxical effect of thought suppression has been considered to be an etiological factor in the development of intrusion-based psychiatric syndromes, such as obsessive-compulsive disorder (OCD; see Wegner, 1989). Notwithstanding the thought suppression paradigm’s relevance for theories of obsession, its implications do not by definition apply to conditions in which intrusive thoughts other than obsessions are crucial (e.g., traumatic memories as occurring in post traumatic stress disorder [PTSD]; American Psychiatric Association, 1994). It is likely that suppression of a single word (e.g., white bear), an obsessional fantasy about jumping before a train, or the memory of a traumatic incident all require different mental operations. For example, one difference is that compared to other target thoughts, a recollection is more elaborated, because it pertains to at least several minutes of an experienced event. In their meta-analysis of suppression experiments, Abramowitz, Tolin and Street (2001) found evidence to suggest that suppression efficacy and target elaborateness are negatively related. In their words: “larger rebound effects were found with nondiscrete target thoughts (e.g., a story) than with discrete thoughts (e.g., a white bear)” (p. 700). In 1996, Wegner, Quillian, and Houston modified the original Wegner, Schneider, Carter and White (1987) thought suppression paradigm in order to make it more suitable as a model of real life situations in which recollections are the target of suppression attempts. These authors showed their participants a film clip and subsequently divided them into suppression, expression, and control groups. Participants had to carry out their instructions for 5 h and then returned to the lab, where their memory of the film was tested. Findings suggested that suppression resulted in a perceived fragmentation of memory (i.e., snapshot likeness). Furthermore, suppression participants performed less well on questions pertaining to the chronology of the film. Based on these findings, Wegner, Quillian and Houston (1996) concluded that suppression has a partial memory undermining potential. In their words: “The snapshot effect of suppression suggests that people might indeed do something that resembles the effect attributed to classical repression” (p. 689). This implies that, contrary to the results of the bulk of thought suppression studies pertaining to discrete thoughts (e.g., white bears), suppression of autobiographical recollections seemed to be partly successful. It is important to note that this differential finding may have to do with the employed dependent variables. Whereas in the original thought suppression study (Wegner et al., 1987), target thought frequency (i.e., intrusive memory) was the main variable, the Wegner et al. (1996) experiment (also) addressed participants’ recollection of the content of the target thought (i.e., explicit memory). To date, a handful of studies has built on the Wegner et al. (1996) work. Rassin (2001) used an audiotaped story as to be suppressed stimulus and found results similar to those reported by Wegner et al. (1996). Rassin, Merckelbach and Muris (1997), however, found that suppressing thoughts of an emotional film clip did not result in a decline of memory. On the contrary, these authors reported that suppression resulted in a paradoxical increase of film-related thoughts, and furthermore in an increased perceived clarity of memory. The conflicting findings may be explained in terms of the employed stimuli. Whereas the Wegner et al. (1996) and the Rassin (2001) study relied on neutral stimuli (a film clip about a union strike, and a written story about a vacation in Spain, respectively), Rassin et al. (1997) used an emotional film (an amateur film of a tourist being attacked by a grizzly bear). Perhaps then, suppression has some desired (i.e.,
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memory undermining) effects in case of neutral memories, but not with emotional recollections. Davies and Clark (1998), as well as Harvey and Bryant (1998) employed the Wegner et al. (1996) paradigm, although these authors were not interested in the effects of suppression on memory, but merely in suppression effects on thought frequency. Davies and Clark (1998) found that suppressing thoughts of an emotional film clip resulted in a rebound of film-related thoughts, while such an effect was absent in case of a neutral film. Interestingly, Harvey and Bryant (1998) reported that suppression resulted in a thought rebound, regardless of whether participants saw a neutral, pleasant, or aversive film clip. These divergent findings across studies may imply that other factors are involved in the determination of suppression efficacy. One such factor may be individual differences in the ability to suppress unwanted thoughts. To date, little is known about the factors that determine which individuals are successful suppressors (see Bowers & Woody, 1996; Kelly & Nauta, 1997; Rutledge, Hancock, & Rutledge, 1996; Rutledge, Hollenberg, & Hancock, 1993). It has been argued that the precise technique use to suppress target thoughts may determine suppression efficacy (Wegner et al., 1987; Wells & Davies, 1994). For example, individuals may suppress a target thought by means environmental distraction, cognitive distraction (e.g., concentrating on recent worries), or mental or physical selfpunishment. Wegner (1994) argued that people might become successful suppressors through practice, but this hypothesis has not yet been tested. Brewin and Beaton (2002) argue that fluid intelligence contributes to the ability to successfully suppress unwanted thoughts. The present study set out to explore the effect of prior expectations on the efficacy of attempts to suppress autobiographical recollections. More specifically, it was tested whether the prior idea that suppression can be successful, actually results in successful suppression. It could be argued that a strong belief in the efficacy of suppression may foster the perception of suppression as a fruitful strategy. In other words, people who are convinced that it is possible to suppress a recollection may actually be better at suppressing recollections (cf. a self-fulfilling prophecy effect). Results from a study by Crombag and Van Koppen (1994) suggest that a vast majority (i.e., 90%) of the respondents (268 healthy volunteers) believes in the possibility of successful suppression. Approximately 50% of these respondents were so convinced of suppression efficacy that they were open to the possibility that they themselves had experienced extremely traumatic events in the past of which they no longer had recollections, due to suppression. The present study sought to explore whether prior expectations about suppression efficacy influence the actual effects of suppression in an experimental set-up.
2. Method 2.1. Participants Eighty-five undergraduate students (69 women) participated in the experiment. Mean age in the sample was 20.60 years (SD = 2.26 years; range: 18–31). Participants were randomly assigned to one of four conditions: a no-instruction-control condition (n = 20), a suppression (per se) condition (n = 20), a “suppression-works” condition (n = 20), or a “suppression-does-not-work” condition (n = 25). There were no age (F[3] ⬍ 1.0) or sex (χ2[3, N = 85] = 4.77, p = 0.19)
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differences between the four groups. Participants were tested individually, and received a small financial compensation. 2.2. Procedure Upon arrival at the laboratory, an audiotaped story was played to the participant (see below). He/she was instructed to identify with the main character in the story. After this, participants were randomly assigned to the control, suppression, suppression-works, or suppression-does-notwork condition. Participants in the no-instruction-control condition were instructed as follows: “During the next two hours you are free to think about anything you want to. You may think of the story, or of anything else. In two hours, you must return to the laboratory in order to complete several questionnaires. The second session will take approximately half an hour”. Participants in the suppression condition received the following written instruction: “During the next two hours you are free to think about anything you want to. However, there is one exception: you must try not to think about the story. If thoughts about the story come into consciousness, you should use any means necessary to make them go away. What you should do, is comparable to what you might be tempted to do if you found out bad news just before an exam. You would try to push that bad news out of your mind during the exam. That is exactly what I would like you to do with every thought of the story—if any—for the next two hours. In two hours, you must return to the laboratory in order to complete several questionnaires. The second session will take approximately half an hour”. Participants in the suppression-works condition received the following additional instruction: “In daily life, people often claim to have suppressed certain memories. Recent studies indicate that it is, indeed, possible to suppress recollections to the point that one cannot remember them. This memory undermining effect has been observed after no more than a few hours. The present study seeks to further investigate the effects of suppression on memory”. Participants in the suppression-does-not-work condition received the following additional instruction: “In daily life, people often claim to have suppressed certain memories. Recent studies indicate, however, that it is impossible to suppress recollections. Moreover, if one tries to suppress a certain recollection, that recollection will come to mind more often. In fact, trying to suppress information is a very good way to remember it well. This effect of improved memory due to suppression attempts has been observed after no more than a few hours. The present study seeks to further investigate the effects of suppression on memory”. Before leaving the lab, participants answered two questions concerning the emotional valence of the story, and their identification with the main character. In the second session, participants were first asked to complete a short questionnaire that was constructed for this study (see below). After this, they had to recall the story as literally as possible. This free recall task was carried out in writing. Following the free recall, participants were asked two final questions (see below). 2.3. Materials The story that was used as stimulus was derived from the work of Wenzlaff, Wegner and Roper (1988). This story is about a person who is late for an important job interview. On his way, he
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speeds and passes a red traffic light. A severe accident in which his car crashes with another is the result. The story ends with a description of the driver of the other car who has a dead infant in her arms. Immediately after the story had been played to the participants, they were asked to rate its unpleasantness on a visual analogue scale (VAS; 0 = not at all unpleasant; 100 very unpleasant). The mean score on this VAS was 67.32 (SD = 24.75) indicating that the story was judged to be fairly unpleasant. Participants were also asked to report the extent to which they could identify with the main character in the story (0 = not at all; 100 = completely). The questionnaire that was constructed for this study consisted of 13 items. The first question (“How many times did you think of the story, during the past two hours?”) pertained to the number of story-related intrusions. Second, the respondent was asked to what extent he/she had tried to engage in suppression. This item, as were all the following, was answered on a VAS (0 = not at all; 100 = very strongly). The third item pertained to the perceived efficacy of suppression attempts (0 = not at all successful; 100 = very successful). The next item asked how accurate participants estimated their own memory of the story (0 = not at all accurate; 100 = very accurate). The following four items pertained to the perceived clarity of participants’ memories (i.e., clarity, detailedness, liveliness, and intensity). These four items were clustered into a mean overall metamemory variable (range: 0–100; Cronbach’s alpha = 0.87), with higher scores indicating that the participant experienced his memory as clearer (these items were adopted from Johnson, Foley, Suengas, & Raye, 1988). Based on the Wegner et al. (1996) findings, the next three items specifically pertained to sequence memory. Participants were asked whether the chronology of the story was still clear to them, whether they thought of the story as a collection of snapshots or as a fluent whole, and whether they, now, tended to think of the whole story or rather only of specific parts of it. These three items were conjoined into one snapshot likeness variable (range: 0–100; a = 0.46), with higher scores indicating perceived snapshot likeness. Lastly, participants were asked the same two questions which they had answered in the morning session, that is, they had to rate the unpleasantness of the story, as well as the extent to which they, now, were able to identify with the main character in the story. As to the scoring of the free recall, the number of correctly recalled propositions was counted (this was done, blind to condition, by the third author). The maximal score on this variable was set at 79 units. As mentioned before, participants answered two final questions after the free recall task. First, they had to indicate how much effort the free recall task had taken. This question was answered on a VAS ranging from 0 (very little) to 100 (very much). The last question asked what the effect of suppression on memory is according to the respondent. This item had a multiple choice answer format with the following three categories: 1) The story is forgotten more rapidly, 2) The story remains better remembered, and 3) Do not know. 3. Results Table 1 presents the mean scores for the control, suppression, suppression-works, and suppression-does-not-work groups on the various variables. As can be seen in this table, several group differences (i.e., thought frequency, suppression effort, perceived suppression efficacy, and
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Table 1 Mean scores (and standard deviations) for the control, suppression, suppression-works, and suppression-does-not-work group on the various variables
Thought-frequency Efforts to suppress Success of suppression Estimated memory accuracy Metamemory (clarity) Snapshot likeness Unpleasantness of the story a Identification with main character a Correctly reproduced details Perceived difficulty of free recall
Control
Suppression
Suppression works
Suppression F(3) does not work
p
3.20 (2.38) 10.55 (12.40) 62.12 (29.49) 71.79 (15.02) 62.75 (20.06) 38.91 (17.77) 53.68 (26.05) 58.11 (24.65)
3.50 (2.26) 64.75 (21.89) 69.00 (26.54) 70.25 (14.55) 64.59 (11.17) 48.48 (17.73) 51.95 (19.80) 44.70 (23.91)
2.90 (1.92) 50.80 (25.05) 79.80 (13.86) 76.95 (15.81) 58.10 (17.64) 45.38 (18.39) 38.30 (19.55) 41.95 (21.97)
6.32 (4.03) 53.52 (24.01) 59.58 (23.00) 68.32 (16.65) 59.50 (15.84) 52.05 (13.70) 57.04 (20.50) 54.28 (22.05)
7.14 ⬍ 0.01 24.31 ⬍ 0.01 3.02 0.04 1.20 0.31 ⬍ 1.00 2.32 0.08 3.08 0.03 2.23 0.09
31.20 (6.23) 32.05 (23.12)
30.50 (6.21) 34.85 (21.97)
30.90 (6.78) 26.95 (20.34)
31.96 (7.12) 29.92 (22.13)
⬍ 1.00 ⬍ 1.00
a Scores displayed in this table were obtained during the second session, although these questions were also asked during the first session, immediately after the story.
unpleasantness ratings) reached significance (a was set at 0.05) in the analyses of variance (ANOVAs). Post hoc analyses (Tukey honestly significant difference) revealed that, with respect to thought frequency, the suppression-does-not-work group scored higher than the other three groups. The difference in suppression effort scores was due to the low score in the control condition. As to perceived suppression efficacy, as well as perceived unpleasantness, the differences were located between the suppression-works and suppression-does-not-work groups. Mean scores of the unpleasantness ratings obtained immediately after the story were 71.05 (SD = 24.09), 61.50 (SD = 25.27), 72.35 (SD = 20.95), and 75.08 (SD = 20.95) for the control, suppression, suppression-works, and suppression-does-not-work group, respectively (F[3] = 1.42, p = 0.24). These scores were analyzed together with the corresponding scores obtained during the second session (see Table 1) in a 4 (groups) x 2 (times) ANOVA with repeated measures on the last factor. Results yielded a main effect of time (F[1] = 59.49, p ⬍ 0.01), and an interaction effect (F[3,82] = 4.12, p = 0.01), but no group effect (F[3] = 1.51, p = 0.22). As to identification with the main character, immediately after having heard the story, control participants scored 66.50 (SD = 23.78), suppression 54.45 (SD = 27.80), suppression-works 60.85 (SD = 21.86), and suppression-does-not-work 67.32 (SD = 21.92): F(3) = 1.32, p = 0.27. Again, these scores were, together with corresponding second time scores, analyzed by means of ANOVA, which yielded a main effect of time (F[1] = 28.82, p ⬍ 0.01), but no group (F[3] = 1.82, p = 0.15), or interaction effect (F[3,82] = 1.21, p = 0.31). The last item pertained to the expected consequences of suppression. Chi-square analysis revealed that participants in the control condition were more strongly convinced that suppression results in a declination of memory than were participants in the three suppression conditions. Suppression-does-not-work instructions seemed to have the most extreme influence, in that none of the participants in this condition reported to believe that suppression has a memory undermining
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effect. This difference was statistically significant: χ2(6, N = 85) = 28.01, p ⬍ 0.01. The frequency of endorsed answers is presented in Table 2. 4. Discussion The main purpose of this study was to investigate the influence of expectations about suppression on the actual efficacy of attempts to suppress recollections. More specifically, it was hypothesized that people who are convinced of the possibility of successful suppression will do better in an experimental set-up in which a recollection of an elaborated stimulus is to be suppressed. What do our findings tell us with respect to this hypothesis? First, given that participants in the three suppression conditions reported equal effort to engage in suppression attempts, it seems that participants who had received the suppression-works instruction actually experienced their suppression attempts as more fruitful than those who had been told that suppression generally does not work. Apparently, the explicit instructions sufficed to create certain expectations, which led participants to perceive their suppression efforts in a concordant manner. Second, the suppression-does-not-work instruction seemed to have resulted in an increased frequency of storyrelated thoughts, while such an increase was not found in the suppression or suppression-works conditions. Third, compared to no-instruction-control, suppression (per se, with positive, or negative instruction) seemed to have no effect on perceived (i.e., estimated accuracy, metamemory, snapshot likeness, and recall difficulty) or actual (i.e., free recall) memory, although the nonsignificant trend (p = 0.08) of suppression participants perceiving their recollections as more snapshot like than did controls, is reminiscent of the findings reported by Wegner et al. (1996). Fourth, the prior expectation that suppression works resulted in decreased unpleasantness ratings after suppression, compared to the expectation that suppression does not work. In summary, our findings suggest that prior expectations about suppression efficacy actually determine perceived suppression efficacy, in an experimental set-up. This self-fulfilling prophecy effect was not limited to perceived efficacy, but also affected the frequency of stimulus-related thoughts, as well as the emotional impact of the stimulus. The induced expectations had no influence on the quality of participants’ explicit recollection of the stimulus material. Given their effect on target thought frequency estimates, prior expectations may explain some of the contradictory Table 2 Number of participants endorsing answers describing expected consequences of suppression in the control, suppression, suppression-works, and suppression-does-not-work Group (N = 85)
Rapid decline of memory Memory improvement Do not know
Control
Suppression
Suppression works
Suppression does not work
11 (55%) 6 (30%) 3 (15%)
4 (20%) 13 (65%) 3 (15%)
6 (30%) 11 (55%) 3 (15%)
0 (0%) 24 (96%) 1 (4%)
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findings obtained in thought suppression research to date. Whereas some researchers found that thought suppression instructions result in immediate and rebound increases of target thought frequency, others failed to find such paradoxical effects (see, for reviews, Abramowitz et al., 2001; Purdon, 1999). Perhaps, part of this contradiction is due to individual differences in the (expectation-driven) capability to suppress target thoughts at will. Contrary to our hypothesis, participants who were convinced of the efficacy of suppression were not found to have poorer explicit memory than participants who were not convinced of suppression efficacy. Apparently, it is possible for people to think of their suppression attempts as successful, without developing poorer recollection of the suppressed information. Perhaps then, participants have evaluated the efficacy of their suppression attempts by using the number of stimulus-related thoughts as criteria, while leaving other possible parameters (such as clarity and estimated accuracy of their recollection) out of the equation. Whereas our results suggest that metacognitions about suppression can diverge from actual accuracy of recollections (see, for comparable divergences, Belli, Winkielman, Read, Schwarz, & Lynn, 1998; Kindt & Van den Hout, in press), Christianson and Bylin (1999) found that metacognition can actually affect memory. These authors instructed their participants to read a story about a murder, and subsequently asked them several questions (including a free recall assignment). After one week, participants, again, had to answer questions pertaining to the story. All participants had to identify with the perpetrator in the story. Half of the participants were instructed to simulate amnesia for the story content, as if they wanted to evade legal responsibility for the crime. This instruction applied to the first interview, while during the second questioning, after one week, all participants had to answer the questions to the best of their knowledge. It seemed that participants who had feigned amnesia during the first interview, recalled fewer details after one week. Hence, simulated amnesia had resulted in actual amnesia. These findings suggest that amnesia may be rooted in cognitive operations that involve metacognitions about memory and amnesia. However, the instructions given to participants in the Christianson and Bylin (1999) study were explicitly directed at amnesia, while our study focused on suppression, leaving the goal of suppression attempts (i.e., absence of intrusions, memory loss, or both) unsaid. Although suppression did not affect explicit memory, results suggest that suppression-works instructions decreased the emotional impact of the recollection. This is in line with Walker, Vogl, and Thompson’s (1997) finding that people tend to minimize the emotional impact of unpleasant memories. Walker, Vogl and Thompson (1997) argue that the reduction of emotional valence is in contradiction with the old Freudian idea of suppression, because their results indicate that people tend to decrease the emotional aspect of unpleasant events, while remembering these events well, whereas Freud claimed that the memory itself becomes inaccessible due to suppression. Evidently, our findings are more in favour of the mechanism proposed by Walker et al. (1997). The main limitation of the present study lies in the circumstance that it is a laboratory model of real-life situations in which people want to suppress memories of traumatic experiences. It seems likely that in real life people are more motivated to get rid of traumatic memories than were the participants in our experiment. Therefore, it might be expected that the influence of expectations on suppression efficacy is more pronounced in real life. Another limitation is the possibility that experimental demand has accounted for a part of the results. However, if experimental demand effects are responsible for the observed group differences, it remains unclear why participants indulged some variables (e.g., thought frequency, perceived suppression efficacy, and
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unpleasantness ratings), but not others (e.g., estimated memory accuracy, metamemory, the free recall task, and perceived difficulty of the free recall task). Although thought frequency and perceived suppression efficacy are obvious variables to be affected by experimental demand, the unpleasantness rating is less so. As to the clinical implications, the current findings contradict the bulk of the suppression research that highlights the inefficacy of suppression attempts (see Abramowitz et al., 2001; Purdon, 1999). Our findings suggest that individuals who are sincerely convinced of suppression efficacy appear to be somewhat successful in their suppression attempts, in that they report experiencing few intrusions. Furthermore suppression appears to alleviate discomfort in the sense that the emotional impact of the suppressed recollection is reduced. To sum up, our study sought to elucidate whether expectations about suppression efficacy determine actual efficacy in an experimental set-up. The data give rise to the following conclusions. First, it seems that expectations regarding suppression efficacy could be manipulated relatively easily (i.e., by means of a short written instruction). Second, induced expectations determined perceived suppression efficacy. More specifically, participants who were told that successful suppression is possible, experienced their suppression efforts as more effective, reported to experience fewer intrusions, and evaluated the stimulus as less aversive, compared to participants who were told that suppression is a counterproductive strategy. The induced expectations did not seem to extend to perceived or actual accuracy of recollections. Third, our findings suggest that, compared to no-instruction-control, suppression had little or no effect on explicit memory. Acknowledgements The first author received a grant from NWO to complete this study. References Abramowitz, J. S., Tolin, D. F., & Street, G. P. (2001). Paradoxical effects of thought suppression: A meta-analysis of controlled studies. Clinical Psychology Review, 21, 683–703. American Psychiatric Association (APA) (1994). Diagnostic and statistical manual for mental disorders. (4th ed.) (DSM IV). Washington: APA. Belli, R. F., Winkielman, P., Read, J. D., Schwarz, N., & Lynn, S. J. (1998). Recalling more childhood events leads to judgments of poorer memory: Implications for the recovered/false memory debate. Psychonomic Bulletin & Review, 5, 318–323. Bowers, K. S., & Woody, E. Z. (1996). Hypnotic amnesia and the paradox of intentional forgetting. Journal of Abnormal Psychology, 105, 381–390. Brewin, C. R., & Beaton, A. (2002). Thought suppression, intelligence, and working memory capacity. Behaviour Research and Therapy, 40, 923–930. Christianson, S., & Bylin, S. (1999). Does simulating amnesia mediate genuine forgetting for a crime event? Applied Cognitive Psychology, 13, 495–511. Crombag, H., & Van Koppen, P. (1994). Verdringen als sociaal verschijnsel [Repression as a social phenomenon]. De Psycholoog, 29, 409–415 in Dutch. Davies, M. I., & Clark, D. M. (1998). Thought suppression produces a rebound effect with analogue post-traumatic intrusions. Behaviour Research and Therapy, 36, 571–582.
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