سرکوب افکار و رسوخ پس از سانحه در دانشجویان مقطع کارشناسی: یک مطالعه همبستگی

Thought suppression (i.e. the process of consciously trying to avoid certain thoughts) is claimed to promote memory loss, but also to increase the frequency of intrusive thoughts (i.e. hyperaccessibility). Although these effects seem contradictory, Wegner, Quillian and Houston [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.] succeeded in reconciling them by postulating the “scene activation” hypothesis. According to this hypothesis, hyperaccessibility of isolated intrusive memories, due to thought suppression, leads to perceived fragmentation (i.e. snapshot likeness) of the memory of the whole event, ultimately resulting in a perception of (partial) memory loss. To investigate this chain of events, undergraduate students (n=110) completed questionnaires about thought suppression and their memories of highly adverse experiences. Correlational analyses revealed that thought suppression was positively related to hyperaccessibility, snapshot likeness, and memory loss. Structural equation modelling elucidated that thought suppression is not necessarily the cause of these memory characteristics.

.In clinical literature, thought suppression refers to conscious attempts to avoid certain thoughts (e.g. Wegner, Schneider, Carter & White, 1987). Obviously, such attempts play a major role in psychopathological conditions that involve recurrent intrusions (see, for a review, Purdon, 1999). For example, people suffering from Post Traumatic Stress Disorder (PTSD; American Psychiatric Association, 1994) commonly report that they engage in thought suppression whenever trauma memories intrude their consciousness (e.g. Amir, Kaplan, Efroni, Levine, Benjamin & Kotler, 1997). There is some dispute as to the precise effects of thought suppression (see, for a review, Rassin, Merckelbach & Muris, 2000). Some authors argue that thought suppression is a counterproductive defence strategy that produces more rather than fewer thoughts about the to-be-suppressed topic (Wegner et al., 1987). By this view, thought suppression induces a state of “hyperaccessibility” of intrusion-linked material (Wegner & Erber, 1992). Other researchers claim that thought suppression may be quite successful and may result in rapid decline (or dissociative amnesia) of suppressed information (e.g. Brewin and Andrews, 1998 and Terr, 1993). Interestingly, a recent laboratory study on suppression and episodic memory by Wegner, Quillian and Houston (1996) found some supporting evidence for the idea that thought suppression may produce both hyperaccessibility and memory undermining effects (but see Rassin, Merckelbach, & Muris, 1997). In that study, students were exposed to a neutral film clip and were subsequently assigned to one of three conditions: a suppression condition in which students were instructed not to think about the film clip during the remainder of the day, a thinking condition in which students were told to think as much as possible about the film clip, and a no-instruction control condition. Five hours later, students returned to the laboratory and were given a memory test covering several aspects of the film clip. Suppression was found to result in a poor memory of event chronology as well as in an altered perception of one's own memory. More specifically, compared to participants in the other conditions, suppression participants more often described their memory of the film clip as a collection of isolated snapshots rather than a moving film. Wegner et al. argue that this snapshot effect (i.e., the loss of sequence memory) may lead people to experience (a specific form of) memory loss. In their words, “the snapshot effect of suppression suggests that people might indeed do something that resembles the effect attributed to classical repression” (Wegner et al. p. 689). Discussing these findings, they succeed in reconciling the memory undermining snapshot effect with the well-documented paradoxical hyperaccessibility effect of thought suppression. According to their “scene activation” hypothesis, it is not the complete memory of the trauma that intrudes consciousness, but rather specific scenes — probably the most emotional and impressive ones. These specific scenes would then become the targets of suppression attempts. This, in turn, would lead to hyperaccessibility of these scenes, but would also compromise overall (sequence) memory of the event. Thus, the hyperaccessibility effect may lead people to experience intense intrusive memories pertaining to specific scenes, but, at the same time, may result in a perception of declined memory of the event as a whole. So far, studies in this domain have been preoccupied with the effects of thought suppression on the frequency of unpleasant intrusions. However, it may well be the case that thought suppression also affects the intensity of such intrusions. For example, the hyperaccessibility of traumatic intrusions may, in some cases, result in the development of exaggerated intrusions. Germane to this issue is a study by Merckelbach, Muris, Horselenberg, and Rassin (1998) who found that 22% of the respondents with traumatic recollections experienced their traumatic intrusions as exaggerations (“worse case scenarios”) of the original event. This finding is, of course, difficult to reconcile with the popular notion that intrusive traumatic memories (i.e. flashbacks) are veridical copies of the original trauma (e.g. Van der Kolk & Fisler, 1995). In discussing these results, Merckelbach et al. speculated that thought suppression may (through its paradoxical hyperaccessibility effect) promote the process of enlargement of traumatic intrusions. Interestingly, in clinical literature, traumatic memories have been characterised as both more and less intense than neutral memories. For example, in a study by Ward and Carroll (1997), victims of sexual assault described their traumatic memories as showing enhanced vividness. In contrast, Koss, Figueredo, Bell, Tharan, and Tromp (1996) reported reduced vividness and clarity of traumatic memories in their sample of rape victims. Possibly, this variety in the phenomenal characteristics of traumatic intrusions has to do with the type of post-trauma elaboration that patients engage in, that is, whether or not they rely on thought suppression. The current study examined the relationship between thought suppression and the characteristics of traumatic intrusions, by analysing questionnaire data. According to Wegner and Zanakos (1994), there are individual differences in the extent to which people rely on thought suppression as a means of dealing with unpleasant thoughts. Some people may engage in thought suppression quite regularly. Therefore, the tendency to cope with unwanted thoughts by suppressing them can be measured. Wegner and Zanakos introduced the White Bear Suppression Inventory (WBSI) as a measure of chronic thought suppression and concluded that suppression, indeed, is a stable defence mechanism. In their words: “…self-reports of thought suppression are reliable over time and thus fulfill an important criterion for recognition as a trait” (Wegner & Zanakos, p. 624). Undergraduate students completed the WBSI and a questionnaire about their most traumatic experience in the past 2 years. It was hypothesised that thought suppression is related to the intensity of trauma-related intrusions (hyperaccessibility effect) as well as to perceived snapshot likeness of traumatic memory (memory undermining effect).

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