The Relationship between Dissociative Tendencies and Schizotypy: An Artifact of Childhood Trauma?

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1 The Relationship between Dissociative Tendencies and Schizotypy: An Artifact of Childhood Trauma? Harvey J. Irwin University of New England Previous research has suggested a relationship between dissociative tendencies and schizotypy. This study sought to extend the previous work in two fundamental respects. First, explicit cognizance was taken of the multidimensionality of both dissociative tendencies and schizotypy. Second, the study examined the possibility that the observed correlation between dissociative tendencies and schizotypy is an artifact of the association between each of these personality domains and a history of childhood trauma. Australian adults (N 116) were administered the Dissociative Experiences Scale, the Schizotypal Personality Questionnaire Brief, and the Childhood Trauma Questionnaire. Hierarchical regression analysis revealed that both pathological and nonpathological dissociative tendencies were predicted by the dimensions of schizotypy, even after the contribution of childhood trauma had been removed. It is concluded that the relationship between dissociative tendencies and schizotypy is not an artifact of childhood abuse, but the clinical significance of this relationship remains to be established John Wiley & Sons, Inc. J Clin Psychol 57: , Keywords: dissociation; schizotypy; childhood trauma The objective of this study was to explore a relationship between dissociative tendencies and schizotypy. In this context, schizotypy is taken to signify not a psychological disorder in itself (as with the diagnostic category of schizotypal personality disorder ), but rather a personality domain that is clinically relevant to the schizophrenia spectrum disorders. Therefore, under the latter usage, the variable of schizotypy is a dimension rather than a dichotomy; that is, the traits that constitute this proneness to schizophrenic-like This project was funded by an Australian Research Council Small Grant. Correspondence concerning this article should be addressed to: Associate Professor H.J. Irwin, School of Psychology, University of New England, Armidale NSW 2351, Australia; hirwin@metz.une.edu.au. JOURNAL OF CLINICAL PSYCHOLOGY, Vol. 57(3), (2001) 2001 John Wiley & Sons, Inc.

2 332 Journal of Clinical Psychology, March 2001 behavior are distributed across the population as a whole and are not confined to any diagnostic group. The dimensional construction of schizotypy now has an impressive conceptual and empirical foundation (Claridge, 1990, 1997; Costello, 1996; Raine, Lencz, & Mednick, 1995). Dissociation is defined as a structured separation of mental processes (e.g., thoughts, emotions, conation, memory, and identity) that are ordinarily integrated (Spiegel & Cardeña, 1991, p. 367). A familiar example of a dissociative experience in everyday life is so-called highway hypnosis, in which a driver on a long trip at times may be deeply engaged in fantasy or other mentation, yet still manage to navigate the vehicle along the road. Here the perceptual and cognitive processes responsible for the performance of driving temporarily are dissociated from consciousness. In a more clinical context, dissociative processes are said to underlie the formal dissociative disorders such as dissociative identity disorder (DID) and depersonalization disorder (Steinberg, 1995). People differ in their capacity or inclination to achieve a dissociated state; that is, dissociative tendencies also have a dimensional nature. Observations in both clinical and nonclinical settings suggest that dissociative tendencies are related to schizotypy. In the clinical population, the differential diagnosis of dissociative disorders and schizophrenia spectrum disorders has long been problematic, and patients with DID are reported to have been especially prone to misdiagnosis as schizophrenics (Bliss, 1980; Boon & Draijer, 1993; Putnam, Guroff, Silberman, Barban, & Post, 1986). This may be due, in part, to a significant overlap of symptoms for the two groups of disorders. Both patients with DID and those with schizophrenia may present with auditory hallucinations, thought insertions, made feelings and acts, withdrawal, paranoia, hostility, belief in paranormal phenomena such as extrasensory perception, identity confusion, and feelings of depersonalization. Indeed, in a study by Ross, Miller, et al. (1990), the average number of Schneiderian symptoms per patient was found to be greater in DID than in schizophrenia. Conversely, schizophrenics scores on a psychometric index of dissociative tendencies also tend to be high, although not as high as those of DID patients (Carlson & Putnam, 1993; Spitzer, Haug, & Freyberger, 1997). Nonetheless, the overlap of dissociative symptoms and the positive symptoms of schizophrenia sometimes may be so great that a patient may meet formal criteria for a dual diagnosis of DID and schizophrenia (Ross, 1997). The association between dissociative tendencies and schizotypy also may extend to the nonclinical population. In a previous study (Irwin, 1998), a dimensional measure of schizotypy was found to be a significant predictor of dissociation (sr 2.23) after the contributions of age and gender had been removed. There are, however, two major limitations of previous indications of a relationship between dissociative tendencies and schizotypy. First, there has been insufficient appreciation of the fact that both dissociation and schizotypy are multidimensional constructs. Waller, Putnam, and Carlson (1996) have shown that there are two conceptually and statistically distinct types of dissociation. One comprises pathological experiences of dissociation such as depersonalization and derealization (Steinberg, 1995), and the other involves nonpathological experiences best exemplified by psychological absorption or strong engrossment in a current activity (Putnam, 1996; Tellegen & Atkinson, 1974). Similarly, schizotypy has been shown to comprise at least three factors (Mason, Claridge, & Williams, 1997; Raine et al., 1994). According to Raine et al. (1994), the cognitiveperceptual component of schizotypy encompasses tendencies toward such schizotypal dysfunctions as magical thinking, unusual perceptual experiences (e.g., hallucinations), paranoid ideation, and ideas of reference (i.e., a neutral environmental event, such as a television program, is taken to have an intended personal meaning). A second, inter-

3 Dissociation, Schizotypy, and Childhood Trauma 333 personal factor reflects deficits in interpersonal functioning, such as social anxiety, lack of close friends, some aspects of paranoia, and blunted affect. Finally, a so-called disorganized facet of schizotypy relates to odd mannerisms and speech. It is essential to take due cognizance of the multidimensional nature of both dissociation and schizotypy to make more specific any relationship between these two constructs. Previous indications of the existence of the relationship have a second limitation namely, that they overlook the possibility that the correlation between dissociative tendencies and schizotypy is spurious. Specifically, the apparent association could be an artifact of each of these variables relationship to a third factor, history of childhood trauma. There is extensive literature documenting the link between dissociative tendencies and childhood trauma, both in clinical (e.g., Coons, Bowman, Pellow, & Schneider, 1989; Putnam et al., 1986) and nonclinical populations (Irwin, 1994b; Sanders, McRoberts, & Tollefson, 1989). Schizotypy, too, has been found to correlate with a history of childhood trauma in clinical (Ross, Anderson, & Clark, 1994) and nonclinical samples (Paterson, 1995; Ross & Joshi, 1992). Investigation of a relationship between dissociative tendencies and schizotypy therefore should control for the potentially confounding factor of childhood trauma. This study sought to pursue the issue without the major shortcomings of previous investigations. The hypothesis of the study was that nonpathological and pathological dissociative tendencies are related to the dimensions of schizotypy, even after controlling for a history of childhood trauma. In undertaking a test of this hypothesis, it was deemed important take account also of potential confounds with age and gender; in some studies, these factors have been found to correlate with both dissociative tendencies (Irwin, 1994a; Ross, Joshi, & Currie, 1990) and schizotypal tendencies (Kremen, Faraone, Toomey, Seidman, & Tsuang, 1998). Participants Method The participants were 116 Australian adults (74 women, 42 men) ranging in age from 18 to 46 years (mean 22.7, median 19, s 7.36). A substantial majority of participants were Introductory Psychology students enrolled at the University of New England, Australia. Previous surveys of this population have found a substantial incidence of various types of childhood trauma (e.g., Irwin, 1994b, 1996) and a wide range of schizotypal tendencies (e.g., Paterson, 1995; Williams, 1994) and dissociative tendencies (e.g., Irwin, 1994b, 1996). Materials Participants completed a self-report questionnaire inventory that included two items on basic demographic characteristics (age and gender), a survey of childhood trauma, and self-report measures of schizotypal and dissociative tendencies. There are very few psychometrically attested questionnaire measures of childhood trauma. The test chosen for the study was the Childhood Trauma Questionnaire or CTQ (Bernstein et al., 1994). The CTQ has 60 items surveying abuse and neglect during the respondent s childhood. The test is comprised of four factorially determined subscales, namely, Physical and Emotional Abuse (23 items), Emotional Neglect (21), Physical Neglect (11), and Sexual Abuse (5). For example, the CTQ includes items on being called stupid, lazy, or ugly by family members (emotional abuse) or being hit hard enough to

4 334 Journal of Clinical Psychology, March 2001 warrant medical treatment (physical abuse); not being encouraged nor feeling loved by family members (emotional neglect); not having clean clothes nor enough to eat (physical neglect); and being fondled or being forced by an adult to engage in sexual activity (sexual abuse). Responses are made on a 5-point Likert scale (1 Never True, to 5 Very Often True). Subscale scores are computed as the sum of responses over the items comprising the respective scale. Initial findings (Bernstein et al., 1994) suggest that the CTQ subscales have strong reliability and validity as measures of self-reported childhood trauma. Thus, the subscales internal reliabilities (Cronbach s ) range from.79 to.94, and test retest reliabilities vary from.80 to.83 over approximately 3.6 months. Convergent and discriminant validity have been demonstrated by strong concurrence between CTQ scores and data derived from both a structured interview (Bernstein et al., 1994) and therapists ratings (Bernstein, Ahluvalia, Pogge, & Handelsman, 1997). Note that the CTQ does not incorporate any procedure for corroborating responses made by participants; it is purely a self-report measure. Schizotypal traits were indexed by Raine and Benishay s (1995) Schizotypal Personality Questionnaire Brief (SPQ-B). Derived from a well-established but lengthy measure of schizotypy (Raine, 1991; Raine et al., 1994), the SPQ-B has 22 dichotomous (Yes/No) items distributed across three factorially determined subscales. The Cognitive Perceptual subscale (8 items) addresses schizophrenia-like cognitive and perceptual deficits such as ideas of reference, magical thinking, unusual perceptual experiences, and paranoid ideation. Items in this subscale pertained, for example, to sensing the presence of a person who is not physically in the vicinity, feeling that others can tell what one is thinking, or feeling that an object or event is a special sign for the respondent. Note that these items are specific to the construct of schizotypy or schizophrenic-like behavior, and are not merely tautological with dissociative experiences. The Interpersonal subscale (8 items) surveys the principal social characteristics of schizotypy, that is, social anxiety and lack of close relationships. The six items in the Disorganized subscale concern odd behavior and speech. Each item answered affirmatively receives a score of 1 point; thus, SPQ-B Cognitive Perceptual and Interpersonal scale scores can range from 0 to 8, and the Disorganized score, from 0 to 6, with higher scores signifying stronger schizotypal tendencies. Judging by data gathered in the course of the test s development (Raine & Benishay, 1995), the reliability and criterion validity of the SPQ-B seem to be highly satisfactory. Internal reliabilities (Cronbach s ) of the subscales range from.72 to.83, and twomonth test retest reliabilities range from.86 to.95. Criterion validity has been ascertained by the observation of significant correlations between the SPQ-B subscales and both another self-report questionnaire measure of schizotypy and dimensional scores derived from a well-established structured clinical interview (SCID-II; Spitzer, Williams, & Gibbon, 1987). Proneness to both pathological and nonpathological dissociation was measured by the Dissociative Experiences Scale (DES), developed by Bernstein and Putnam (Bernstein & Putnam, 1986; Carlson & Putnam, 1993). The DES is a 28-item self-report measure indexing the frequency of various experiences of dissociative phenomena in the respondent s daily life. For example, one item concerns looking into a mirror and not recognizing oneself (an instance of pathological dissociation); another item concerns lack of awareness of nearby events while watching television or a movie (an instance of psychological absorption). With the version of the DES used here, for each item the participant is instructed to circle a number on a 21-point scale (from in 5% increments) to indicate the percentage of time they have the nominated dissociative experience. The DES has been shown to have good reliability (Cronbach s.95, test retest reliability.79 to.96; Carlson & Putnam, 1993; Frischholz et al., 1990), and its con-

5 Dissociation, Schizotypy, and Childhood Trauma 335 current and discriminative validity has been documented extensively (Carlson & Putnam, 1993; Frischholz et al., 1991; van IJzendoorn & Schuengel, 1996). For the purposes of this project the DES was used to generate two scores for each participant. One score, based on eight items of the scale, indexed the pathological form of dissociation (the DES-T; Waller et al., 1996). The second score, derived from 12 DES items in the case of nonclinical samples (Ross, Ellason, & Anderson, 1995), is a measure of psychological absorption, the key nonpathological dimension of the dissociative domain (Putnam, 1996). Scores on both of these facets of dissociation are computed as the mean of responses to the component items and thus can range from 0 to 100. On each scale, high scores signify strong (pathological or nonpathological) dissociative tendencies. Procedure Potential participants were approached either individually or in class groups and told about the general nature of the survey. A plain language statement was attached to the front of the inventory proffered to potential participants. This statement described the topic of the study, stressed that participation was voluntary, and explained that the return of the completed form would in itself be taken to signify informed consent to participate in the project. An appeal also was made to participants to respond to all questionnaire items as spontaneously and openly as possible. People who agreed to participate returned their completed forms in an envelope supplied by the researcher. Results Descriptive statistics (mean and standard deviation) on the experimental variables are given in Table 1. These data are comparable with the performance of other college samples on the CTQ (Irwin, 1998), SPQ (Raine & Benishay, 1995), and DES (Irwin, 1999a). It should be noted also that schizotypy and pathological-dissociation scores range up to clinically significant levels (Carlson & Putnam, 1993; Raine & Benishay, 1995). For completeness of information, Pearson correlations also are provided (Table 2). Table 1 Means, Standard Deviations, and Ranges of Scores on Experimental Measures (N = 116) Scale xs s Range DES Subscales Nonpathological (Absorption) Pathological (DES-T) SPQ-B subscales Cognitive Perceptual Interpersonal Disorganized CTQ Subscales Physical and emotional abuse Emotional neglect Physical neglect Sexual abuse

6 336 Journal of Clinical Psychology, March 2001 Table 2 Pearson Correlations between Experimental Measures (N = 116) Scale (2) (3) (4) (5) (6) (7) (8) (9) DES Subscales (1) Nonpathological (Absorption).75***.53***.41***.48***.31***.17.21*.19* (2) pathological (DES-T).50***.33***.45***.28**.21*.23*.14 SPQ-B Subscales (3) Cognitive Perceptual.45***.52***.46***.36***.34***.21* (4) Interpersonal.46***.28**.28**.26**.08 (5) Disorganized.39***.32***.31***.20* CTQ Subscales (6) Physical and emotional abuse.80***.81***.50*** (7) Emotional neglect.68***.40*** (8) Physical neglect.46*** (9) Sexual abuse *p.05; **p.01; ***p.001 (two-tailed, uncorrected) Under the hypothesis that the relationship between dissociative and schizotypal tendencies is an artifact of childhood trauma, the relationship between dissociation scores and schizotypy scores should be eliminated when the contribution of the childhood trauma is partialled out. To test this hypothesis, two hierarchical (or sequential) multiple regressions (Tabachnick & Fidell, 1996) were performed between dissociation (DES Absorption and DES-T) scores as the dependent variable in each case and the dimensions of schizotypy (SPQ-B subscales), childhood trauma (CTQ subscales), age, and (female) gender as independent variables. The analyses were conducted using SPSS (1995) regression software and comprised the following hierarchical steps. Age and gender were entered first in order to accommodate the effects of these extraneous variables; in some studies, these factors have been found to correlate with both dissociative tendencies (Irwin, 1994a; Ross, Joshi, & Currie, 1990) and schizotypal tendencies (Kremen et al., 1998). In the next step, the four dimensions of the CTQ were entered in stepwise fashion; this permitted an assessment of the relative contribution of four types of childhood trauma as predictors of dissociative tendencies. The schizotypy scores were entered in stepwise fashion in the final step of the hierarchical analysis; this provided a test of the possibility that schizotypy has no bearing on dissociative tendencies after due allowance has been made for childhood trauma. The nonpathological dissociation or DES Absorption scores were skewed significantly; this problem was overcome by applying a square-root transformation before the regression analysis of these scores. A complete hierarchical decomposition is presented in Table 3. All tolerance statistics were well above zero, ranging from.20 to.80; therefore, multicollinearity of predictor variables was of no practical concern (Darlington, 1990). Table 3 shows the unstandardized regression coefficients (B), the hierarchical sums of squares (HSS) with associated degrees of freedom (df ), the associated F and p values for the contributions of each variable to the regression, the hierarchical semipartial correlations (hsr 2 ), and R, R 2, and adjusted R 2. After the first step of the regression analysis, with age and gender in the equation, R 2 was.01 [F(2,113).47, p.62]. Entry of the childhood-trauma scores in the second step increased R 2 to.13 [F(6,109) 2.75, p.016]. In the final step of the hierarchical analysis, with the addition of the schizotypy factors, R 2 increased further to.41 [F(9,106)

7 Dissociation, Schizotypy, and Childhood Trauma 337 Table 3 Hierarchical Multiple Regression of Schizotypy (SPQ-B), Childhood Trauma (CTQ), Age and Gender on Nonpathological Dissociative Tendencies (DES Absorption), Showing Complete Hierarchical Decomposition (N = 116) Variables B HSS df F p hsr 2 Age ns.00 Gender ns.01 CTQ Subscales Physical and emotional abuse Emotional neglect ns.01 Physical neglect ns.00 Sexual abuse ns.00 SPQ-B Subscales Cognitive perceptual Interpersonal Disorganized Residual Total R 2.41, adjusted R 2.36, R.64, p Reported p value is for a two tailed test of the hypothesis that R , p.0001]. Thus, the three schizotypy factors contributed to the prediction of nonpathological dissociation scores, even after account had been taken of the contribution of childhood trauma. The pathological dissociation or DES-T scores also were skewed; a correction for this necessitated both the application of a square-root transformation and the exclusion of two (high) outliers, following the criteria enunciated by Tabachnick and Fidell (1996). A complete hierarchical decomposition for the second regression analysis is presented in Table 4. After the first step of the regression, with age and gender in the equation, R 2 was.004 [F(2,111).18, p.82]. Entry of the childhood-trauma scores in the second step increased R 2 to.09 [F(6,107) 1.81, p.102]. In the final step of the hierarchical analysis, with the addition of the schizotypy factors, R 2 increased further to.41 [F(9,104) 8.16, p.0001]. Thus, the three schizotypy factors contributed to the prediction of pathological dissociation scores, even after account had been taken of the childhood trauma scores. Discussion The findings of the study strongly suggest that the relationship between dissociative tendencies and schizotypy is not a mere artifact of a history of childhood trauma. The results of the hierarchical regression analyses for nonpathological dissociation (psychological absorption; Table 3) and pathological dissociation (Table 4) are so similar that they best are discussed collectively. Aspects of childhood trauma contributed to the prediction of both facets of dissociation. In the sample of Australian adults, trauma seemed to be marginally more predictive of psychological absorption (aggregate sr 2.12) than of pathological dissociation (aggregate sr 2.09). Previous investigations have suggested that the reverse more often may be the case (DiTomasso & Routh, 1993; Irwin, 1999b). In any event, the significant

8 338 Journal of Clinical Psychology, March 2001 Table 4 Hierarchical Multiple Regression of Schizotypy (SPQ-B), Childhood Trauma (CTQ), Age, and Gender on Pathological Dissociative Tendencies (DES-T) Showing Complete Hierarchical Decomposition (N = 114) Variables B HSS df F p hsr 2 Age ns.00 Gender ns.00 CTQ Subscales Physical and emotional abuse Emotional neglect ns.01 Physical neglect Sexual abuse ns.00 SPQ-B Subscales Cognitive perceptual Interpersonal ns.01 Disorganized Residual Total R 2.41, adjusted R 2.36, R.64, p Reported p value is for a two tailed test of the hypothesis that R 0. contribution by childhood trauma to both regressions vindicates the proposal to remove this contribution before assessing any residual relationship between dissociative tendencies and schizotypy. When the factors of childhood trauma were controlled, a relationship persisted between dissociative tendencies and schizotypy. The contribution of schizotypy may have been slightly stronger for pathological (aggregate sr 2.33) than for nonpathological dissociation (aggregate sr 2.28). For the two facets of dissociation, the contributions of the three schizotypy factors were broadly similar, with the cognitive perceptual factor having the strongest relationship, followed in order by the disorganized factor and the interpersonal factor. The contribution of the last of these factors was not significant statistically in the case of pathological dissociation (Table 4), but the pattern of the relationships sufficiently was comparable across the two hierarchical regressions that the nonsignificant result for the interpersonal factor in one analysis perhaps should not be given undue emphasis. In this light, it is reasonable to conclude that much the same combination of the three components of schizotypy is predictive of both pathological and nonpathological dissociative tendencies, with the cognitive perceptual domain of schizotypy particularly being crucial and the strength of the relationship being slightly greater for pathological dissociation than for nonpathological dissociation. An anonymous reviewer of this article had cautioned that the above relationship might be a mere confound of item overlap between the measures of dissociation and of schizotypy. Two arguments may be raised against this view. First, inspection of the DES items and of the Cognitive Perceptual subscale of the SPQ-B does not reveal any item in the two scales that bears on the same or a similar experience; the items of the DES pertain to specifically dissociative phenomena and those of the SPQ-B address specifically schizotypal processes. Second, post-hoc item analyses indicated that the relationship between the cognitive perceptual facet of schizotypy and both pathological and nonpathological dissociation was not limited to a few items (with similar content or otherwise). Rather,

9 Dissociation, Schizotypy, and Childhood Trauma 339 dissociation correlated with all but one of the items of the Cognitive Perceptual subscale of the SPQ-B; the sole nonpredictive item concerned the feeling that others were noticing one when shopping. Therefore, the observed relationships do not appear to be an artifact of a content overlap of the measures. Nevertheless, some cautionary comments are appropriate on the identification of the cognitive perceptual component of schizotypy as the primary predictor of dissociative tendencies. This factor of schizotypy, it will be recalled, denotes tendencies toward such schizotypal dysfunctions as magical thinking, unusual perceptual experiences (e.g., hallucinations), paranoid ideation, and ideas of reference. Several of these characteristics may well be common to dissociative and schizotypal experiences, but some of the commonalities might be rather superficial. Paranoia, for example, principally may be a type of thought disorder in schizotypy, but in people with dissociative tendencies, paranoia may be more a consequence of others reactions to the oddness of dissociative behaviors. Similarly, if clinical cases are a valid guide, the experience of voices (auditory hallucinations) differs phenomenologically between the two domains; during dissociation, the voices are experienced as coming from within, whereas in schizotypal experiences, the voices typically are taken to have an external source. Thus, some of the above characteristics may differ in meaning between the dissociative and the schizotypal experience. A similar argument may be mounted in relation to the remaining two schizotypy factors. This possibility, in addition to the fact that less than half of the common variance is accounted for in each regression analysis, serves to caution against any simplistic interpretation of the study s findings as evidence for the intrinsic equivalence of dissociative and schizotypal processes. The relationship between dissociation and schizotypy may exist, in part, at a very superficial level. Again, the suggested involvement of magical thinking in both schizotypy and dissociative tendencies perhaps could be interpreted to indicate a more fundamental overlap of processes in these domains. It is possible that in order for a schizotypal person to engage in magical thinking, some dissociative skills are required. Specifically, magical thinking may depend upon the suspension or dissociation of any information or process of reality testing that would discount the rationality of the person s line of thought. Conversely, having dissociative tendencies may predispose a person to dissociating from the harsh realities of life and thence to an indulgence in magical thinking. Thus, in the prediction of dissociative tendencies, the substantial contribution of the cognitive perceptual factor of schizotypy may be due largely to the process of magical thinking. Further investigation of these views would be possible using an appropriate measure of magical thinking as a construct in its own right (Eckblad & Chapman, 1983). It is possible, therefore, that the concept of magical thinking could help, in a small way, to illuminate the nature of the dissociative disorders, and the notion of dissociative capacity might account equally for some presentations of the schizophrenia-spectrum disorders. At the same time, the prospects for such application should not be overstated. As suggested earlier, much of the commonality between dissociative tendencies and schizotypy may be purely superficial and might not provide any major insights into underlying etiological processes. Certainly, it is possible that (inherited) schizotypal personality involves pathological and nonpathological dissociative tendencies that may be intrinsic to the expression of some schizophrenic symptoms, but this is a matter for resolution through future empirical enquiry. Additionally, although the schizotypy and pathologicaldissociation scores of some participants did reach clinically significant levels, the relationships educed here remain to be demonstrated in a clinical population. In conclusion, the relationship between dissociative tendencies and schizotypy evidently is not an artifact of a history of childhood trauma. The clinical significance of the relationship nevertheless remains to be established.

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