Individuals with obsessive-compulsive disorder are less prone to false memories

Journal of Obsessive-Compulsive and Related Disorders 10 (2016) 62–68

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Journal of Obsessive-Compulsive and Related Disorders journal homepage: www.elsevier.com/locate/jocrd

Individuals with obsessive-compulsive disorder are less prone to false memories İlyas Göz a, Sibel Kılınç Karahan b, Ali İ. Tekcan c,n a

Acıbadem University, Department of Psychology, İstanbul 34857, Turkey Keçiören Eğitim ve Araştırma Hastanesi, Ankara 06380, Turkey c Bogazici University, Department of Psychology, İstanbul 34342, Turkey b

art ic l e i nf o

a b s t r a c t

Article history: Received 25 February 2016 Received in revised form 29 May 2016 Accepted 30 May 2016 Available online 31 May 2016

Previous research on memory and metamemory processes in obsessive compulsive disorder (OCD) almost exclusively addressed veridical memory. The present study investigated veridical and false memory (recall and recognition of nonpresented information) as well as confidence in OCD. We compared checker OCD, non-checker OCD, and healthy control participants (HC) by using the Deese-Roediger-McDermott (DRM) false memory paradigm. Participants were given word lists, each of which consisted of semantically related words which were strong associates of a non-presented critical target word. They were then given a free recall and a recognition task. Although both OCD groups showed comparable correct recall and recognition performance to that of the HC group, OCD groups were less prone to false memories and reported lower confidence for these false memories than the HC group. Accuracy of global recognition estimates were similar across three groups. This pattern of results may partly be due to OCD groups’ reliance on item-based rather than relational processing at encoding. & 2016 Elsevier Inc. All rights reserved.

Keywords: OCD Memory False memory Confidence Checking

1. Introduction 1.1. Memory and metamemory in OCD A substantial amount of research addressed the role of higherorder cognitive processes in the etiology and maintenance of checking symptoms associated with obsessive-compulsive disorder (OCD). These include, among others, attention, executive functions, memory, and planning (for meta-analyses see Abramovitch, Abramowitz, & Mittelman, 2013; Cuttler, & Graf, 2009; Shin, Lee, Kim, & Kwon, 2014; Woods, Vevea, Chambless, & Bayen, 2002). The present study focused on episodic memory and metamemory in patients diagnosed with OCD. Episodic memory has been a central issue in OCD especially in relation to checking compulsions, because it has been argued that checking behavior might be caused, at least partly, by episodic memory deficits (e.g., Exner, Martin, & Rief, 2009). Several studies testing this relationship found OCD participants with primary checking symptoms to be weaker in terms of episodic memory performance compared to healthy control (HC) participants (e.g., Exner et al., 2009; Sher, n Correspondence to: Boğaziçi University, Department of Psychology, Bebek, 34342 Istanbul, Turkey. E-mail address: [email protected] (A.İ. Tekcan).

http://dx.doi.org/10.1016/j.jocrd.2016.05.004 2211-3649/& 2016 Elsevier Inc. All rights reserved.

Frost, & Otto, 1983; Tükel et al., 2012; Tuna, Tekcan, & Topçuoğlu, 2005; Zitterl et al., 2001). However, some studies suggested that this difference might depend on the type of material (Deckersbach, Otto, Savage, Baer, & Jenike, 2000; Savage et al., 1999) and still others found no difference between groups (Foa, Amir, Gershuny, Molnar, & Kozak, 1997; MacDonald, Anthony, MacLeod, & Richter, 1997; Moritz, Kloss, von Eckstaedt, & Jelinek, 2009). Although the results of individual empirical studies do not present a very clear picture, a number of meta-analyses suggest that verbal memory is poorer in OCD or analogue groups. In their meta-analysis, Woods et al. (2002) found that checkers (sub-clinical checker and OCDchecker groups combined) were poorer than controls in free and cued recall of verbal material. Cuttler et al. (2009) concluded that one of the areas where OCD groups showed deficits in comparison to control participants was verbal memory. Two recent metaanalyses also found poorer verbal memory in OCD groups compared to non-diagnosed control groups (Abramovitch et al., 2013; Shin et al., 2014). Although all of these studies found significant differences in effect sizes, they tended to be smaller for verbal memory than for non-verbal memory (e.g., Abramovitch et al., 2013). More recently, metamemory processes have been receiving attention with regard to checking behavior in OCD. Metamemory refers to monitoring and control of the content, processes, and outcomes of memory (Metcalfe, 2009; Nelson, & Narens, 1990). Several lines of evidence point to metamemory deficits in OCD

İ. Göz et al. / Journal of Obsessive-Compulsive and Related Disorders 10 (2016) 62–68

checkers. It has been shown that OCD checkers are less confident in the accuracy of the retrieved episodic information than control participants (MacDonald et al., 1997; McNally, & Kohlbeck, 1993). They are also less confident and less accurate in prospective metamemory judgments such as feeling of knowing (Tuna et al., 2005). It has been argued that deficits in metamemory (e.g., low confidence) may have a causal role in checking behavior. For instance, Alcolado, and Radomsky (2011) experimentally showed that participants with low memory confidence were more likely to have the urge to check. It has also been suggested that repeated checking might have the effect of decreasing subjective sense of remembering/recollection, thereby increasing checking behavior. For instance, van den Hout, & Kindt (2003a) showed that engaging in repeated checking leads to a decrease in vividness and detail of memories, despite no change in accuracy. Radomsky, Dugas, Alcolado, and Lavoie (2014) found that individuals diagnosed with OCD as well as nonclinical participants reported lower memory confidence and vividness after repeated checking (see also, Radomsky, & Alcolado, 2010; van den Hout, & Kindt, 2003b). It has to be noted that in their comprehensive review, Cuttler et al. (2009) concluded that there was no difference between checker-OCD and non-checker OCD groups in either memory or metamemory performance. 1.2. False memory in OCD As noted by Klumpp, Amir, and Garfinkel (2009) almost all research on episodic memory-OCD relationship have investigated veridical memory performance. Indeed, this has also been true for metamemory. We agree with Klumpp et al. (2009) that memory errors or false memories may also be very informative regarding both memory and metamemory processes in OCD. In the only study addressing false memory in OCD, Klumpp et al. (2009) looked at memory errors by using a procedure similar to the Deese-Roediger-McDermott paradigm (DRM; Deese, 1959; Roediger, & McDermott, 1995) in college students with high vs. low washing scores. In a typical study using the DRM paradigm, participants study several word lists each of which consists of related words (e.g., rest, bed, blanket, snooze etc.) that are semantic associates of a non-presented word in the list, known as the critical lure (in this example, sleep). At the end of each list participants are given memory tests, with the main variable being the memory for non-presented critical item. Results of several studies show that participants tend to falsely recognize the critical lure as having been studied (e.g., Gallo, & Roediger, 2003; Roediger et al., 1995). Moreover, these false memories are associated with a strong sense of remembering and vividness (e.g., Roediger et al., 1995) and are largely immune to forewarning (e.g., Gallo, Roberts, & Seamon, 1997). Several studies employed the DRM procedure in order to elucidate the cognitive mechanisms in clinical populations, including depression (Yeh, & Hua, 2009) and bipolar disorder (Schilling, Wingenfeld, Spitzer, Nagel, & Moritz, 2013). In their study, Klumpp et al. (2009) modified the classical DRM procedure. Participants studied positive, neutral, and threat-relevant scenarios and then were given a recognition test, in which they were presented with words studied as part of the scenarios as well as nonstudied words. In the test, they were asked to indicate studied words as “old” and nonstudied words as “new”. For words given an “old” judgment, participants also made a Remember/ Know judgment to assess the subjective experience of remembering (Gardiner, & Richardson-Klavehn, 2000; Tulving, 1985; van den Hout et al., 2003a). Remember judgments refer to positive recognition (“old”) decisions based on some perceptual/contextual information about having studied the stimuli. Know judgments refer to positive recognition judgments based on knowledge, without any associated perceptual or contextual detail (Gardiner

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et al., 2000; Tulving, 1985). It is argued that Know judgments are likely to be based on the familiarity with the studied material in the absence of specific details. Klumpp et al. (2009) found no group difference in the overall correct recognition. However, the OC group showed higher false recognition than control participants, but only for threat-relevant words that were associated with Know rather than Remember type of judgments, indicating more reliance on familiarity. The authors suggested that these familiarity based judgments may add to uncertainty experienced by individuals with OCD. The DRM procedure, which has been a canonical technique to demonstrate false memory, is very appropriate for studying memory as well as metamemory. First, it measures correct and false memory for the same set of stimuli. Second, although it is possible to investigate false memory (especially intrusion errors) with typical free recall tasks, false memory rates in these studies are very low, making it very difficult to study possible effects of different independent variables. The DRM technique, on the other hand, leads to robust and consistent false memory effects. Third, in this technique participants may report a strong sense of recollection for the material they tend to falsely remember, allowing researchers to dissociate accuracy and confidence. Given the central role confidence is argued to play in checking behavior (e.g., van den Hout et al., 2003a), these characteristics make the DRM paradigm a useful tool to address the confidence associated with experienced vs non-experienced events. 1.3. The present study In the present study, we investigated memory and metamemory for veridical and false memory performance using the DRM paradigm. More specifically, because OCD (especially checking behavior associated with it) is arguably linked to episodic memory deficits (Abramovitch et al., 2013; Cuttler et al., 2009; Shin et al., 2014; Woods et al., 2002), all published work on memory processes in OCD addressed forgetting of studied information (omission errors). The present study is the first to look at false memory (remembering information that has not been studied) in individuals diagnosed with OCD, thereby providing novel data regarding the boundaries of memory and metamemory performance in OCD. Moreover, inclusion of participants diagnosed with OCD with and without primary checking symptoms provides a chance to address the role of checking symptomatology on memory (Cuttler et al., 2009). Research also shows that episodic memory deficits in OCD may result from weak strategic organization in patients (Buhlmann et al., 2006; Cabrera, McNally, & Savage, 2001; Deckersbach et al., 2000; Melloni, Urbistondo, Sedeno, Gelormini, Kichic, & Ibanez, 2012). As such, DRM paradigm becomes especially useful since false memory in DRM is based on implicit semantic activation of strongly associated information existing in memory (e.g., Gallo, 2010). Thus, it provides an opportunity to test both accurate and false memory performance without the need for strategic organization at encoding. As noted in the introduction, a number of meta-analyses showed that verbal memory tasks show small effect sizes in OCDHC comparisons. Given that providing semantically organized lists minimizes negative effects of strategic organization deficits in OCD groups, we expected that accurate episodic memory performance would be less affected by the quality of participant-initiated strategies, leading to a small deficit in the OCD groups in correct recall and recognition compared to the HC group. Research with neuropsychological tests consisting of semantically associated items such as California Verbal Learning Test (CVLT) also support this prediction (e.g., de Geus, Denys, Sitskoorn, & Westenberg, 2007). In terms of false memory, the activation of the critical lure is

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considered to be automatic, i.e., when the list words which are strong associates of the critical lure are studied, the critical lure is strongly activated. It has also been shown that it is difficult to limit this activation through forewarning (e.g., Gallo et al., 1997). This automaticity of semantic activation combined with the fact that organized study lists are likely to help correct memory performance, we expected a comparable performance. In our study we extend the work by Klumpp et al. (2009) in a number of ways. First, whereas Klumpp et al. (2009) used analogue groups, we employed individuals diagnosed with OCD. Moreover, we recruited approximately equal number of checker vs. non-checker OCD participants to address the role of checking symptomatology on memory and metamemory. Finally, we collected recall and recognition data for gauging correct as well as false memory.

2. Method 2.1. Participants Ninety participants (60 patients diagnosed with obsessivecompulsive disorder and 30 healthy control participants) took part in the study. The patients were recruited from the outpatient clinic of a state hospital in İstanbul, Turkey. All patients in the sample were diagnosed by a psychiatrist and a clinical psychologist independently on the basis of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) criteria (American Psychiatric Association, 2000). After the initial diagnostic interview by the psychiatrist, the clinical psychologist interviewed the participants using the Structured Clinical Interview for DSM IV (SCID-I; First, Spitzer, Gibbon, & Williams, 1997). The primary diagnosis was OCD for all patients. The comorbid diagnoses were major depressive disorder (n ¼22), generalized anxiety disorder (n ¼10), somatization disorder (n ¼3), brief psychotic disorder (n ¼3), mood disorder (n ¼2), agoraphobia (n ¼2), specific phobia (n ¼1), dysthymic disorder (n ¼1) and hypochondriasis (n¼ 1). For 28 of the OCD participants primary symptom was checking (checker OCD), and for 32 it was other than checking (non-checker OCD). Majority of the participants were women in all groups, with percentages ranging from 63% to 75%. The healthy control participants (HC) were recruited from among the hospital staff or patient relatives (n ¼ 4), and were judged to have no current diagnosis or a history of Axis I disorder on the basis of a diagnostic interview (SCID-I). Descriptive data regarding demographic as well as other background characteristics are given in Table 1. Table 1. Descriptive data for the background variables. Checker OCD

Age Education MOCI Y-BOCS BDI STAI-S STAI-T

Non-checker OCD

HC

M

SD

M

SD

M

SD

F

p

31.53 8.14 19.21a 24.68 18.89a 40.29a 52.18a

10.81 3.50 5.86 8.34 11.46 5.08 5.86

34.34 7.00 21.75a 21.59 26.31b 41.66a 50.66a

9.69 3.05 6.02 8.07 10.51 6.00 7.81

34.73 7.80 12.50b – 10.10c 43.00b 47.27b

11.08 3.31 5.76 – 6.52 5.84 5.77

.79 .97 20.18 2.12 21.60 1.66 4.26

.46 .38 .00 .15 .00 .20 .02

Notes. Means in the same row that do not share the same superscript are different at po .01. The df for the F statistic are 1.58 for Y-BOCS and 2.87 for the remaining variables. Only the two OCD groups are compared on Y-BOCS.

2.2. Materials 2.2.1. Memory materials We used the Deese-Roediger-McDermott (DRM) paradigm. There were 6 lists of 13 words each. The word lists for the DRM task we used were developed and validated by Göz (2005). The details of the task are explained in the Procedure section. 2.2.2. Maudsley Obsessional-compulsive Inventory (MOCI; Hodgson, & Rachman, 1977) consists of 30 Yes-No statements measuring the severity of OCD symptoms on four subscales (cleaning, checking, doubting, and slowness). Erol and Savaşır (1988) demonstrated the validity of MOCI in a Turkish sample. Cronbach alpha for the total MOCI scores in the present samples ranged between .690 and .884 for the three groups, indicating satisfactory internal reliability. 2.2.3. Yale-Brown Obsessive Compulsive Scale (Y-BOCS; Goodman, Price, Rasmussen, Mazure, & Fleischmann, 1989; Goodman, Price, Rasmussen, Mazure, Delgado et al., 1989) is a clinician-administered screening and severity-measurement instrument, and consists of a symptom checklist for obsessive compulsive symptoms. Tek et al. (1995) showed the Turkish version of this instrument to be valid and reliable. 2.2.4. State – Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, Luschene, Vagg, & Jacobs, 1983) consists of 40 Likert – type items measuring an individual's anxiety at that time and in general. The Turkish version has been shown to be reliable and valid (LeCompte, & Öner, 1975; Öner, 1978). Cronbach alpha values for the total STAI ranged between .638 and .722 for the three groups. 2.2.5. Beck Depression Inventory (BDI; Beck, Ward, Mendelsohn, Mock, & Erbaugh, 1961) is a self-report instrument measuring the severity of depressive symptoms. Hisli (1988) showed the Turkish version to be valid and reliable. Cronbach alpha values ranged between .749 and .924 for the three groups. 2.3. Procedure All participants were individually tested by a clinical psychologist in a testing room in an hospital setting. Each participant was presented with six consecutive study lists in auditory format. Each word was presented for one second. At the end of each list participants were asked to recall as many of the words as possible from the just-studied list and write them on a blank sheet of paper in a 3 min period. This procedure was repeated until all 6 lists were presented and recalled. Once the recall of the last list was completed, participants were given a multiple-choice recognition test. The 54-item recognition test included 12 studied items (two from each of 6 lists) and 42 nonstudied items. There were four types of nonstudied items (distractors): (a) the six critical lure words from which the study lists were generated (e.g., money), (b) 12 semantically related words (two per studied list), (c) 12 phonologically related words (two per studied list), and (d) 12 words which were semantically and phonologically unrelated to the lists (two per studied list). All the distractors in the recognition test were high-frequency words with a frequency of 100 or higher per million (Göz, 2003). For each word, participants indicated whether they studied it or not. In addition, after each recognition decision, participants indicated how confident they were in their recognition decision on a 4-point scale (from 1– not confident at all to 4 – very confident).

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Finally, in order to get a global retrospective metamemory estimate, participants were asked to estimate their correct recognition performance as a percentage. Once the memory phase of the experiment was completed, participant filled out the questionnaires described in Section 2. The OCD participants were given all the scales, whereas the HC participants were given the MOCI, the BDI, and the STAI. Each session took approximately 2–2.5 h.

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semantic, phonological, and unrelated lures. To put the critical lure findings into context, we looked at whether other types of critical lures differ across groups. Percentage of false alarms across HC, checker OCD, and non-checker OCD groups did not differ for semantic (47%, 42%, and 50%), phonological (13%, 10%, and 17%), or unrelated lures (3%, 4%, 8%). Separate one-way ANOVAs revealed that the three groups did not differ from each other in any of the lures, all Fs (2, 87) o1.6, ps 4 10. 3.3. Item-based confidence judgments

3. Results We investigated the effect of group (checker OCD, non-checker OCD, and HC) on each memory and metamemory measure. Descriptive statistics are given in Table 2. 3.1. Recall 3.1.1. Correct recall There was no group effect on percentage of correct recall, F(2, 87) ¼ 1.85, MSe ¼ 177.25, p ¼ .16, η2 ¼.04. 3.1.2. False recall of critical lures The main variable of interest in false memory studies using the DRM paradigm is memory performance for the critical lures (items not presented in the study list but associatively linked to all the studied words). There was no effect of group on percentage of false recall, F(2, 87) o1, MSe ¼ 383.50, p ¼ .46, η2 ¼.02.

To assess retrospective metamemory, each participant was asked to rate, on a 4-point scale from 1 (not confident at all) to 4 (very confident), the degree to which he/she was confident in each of his/her recognition judgments. As can be seen in Table 2, the mean confidence ratings for the studied items were above the mid-point of the scale for all groups. There was no group effect, F(2, 87) ¼ 1.44, MSe ¼ .242, p ¼.24, η2 ¼.03. For falsely recognized items, there was a strong effect of group on confidence ratings, F(2, 87) ¼ 24.10, MSe ¼.321, p o.001, η2 ¼.36. Post-hoc Tukey's HSD tests showed that both the checker OCD (M ¼ 1.95) and non-checker OCD (M ¼ 1.94) participants were less confident in their endorsement of the critical lure items than the HC participants (M ¼ 2.70). 3.4. Global recognition estimates

3.2.2. False recognition of critical lures There was a robust effect of group, F(2, 87) ¼ 51.19, MSe ¼ 370.38, p o.001, η2 ¼.54. Post-hoc Tukey's test showed that false recognition percentage was substantially higher for the HC group (M ¼65%) than the checker OCD (M¼19%) and the non-checker OCD (M ¼ 24%) groups.

We also investigated group differences in confidence through global rather than item-based judgments. Therefore, once the recognition task was finished, our participants were asked to estimate the percentage of items they recognized correctly. The mean recognition percentage estimates (with standard deviations) were 55.96 (30.53) for checker OCD, 54.56 (27.62) for non-checker OCD, and 64.10 (18.02) for HC participants. The groups were not different from each other, F(2, 87) ¼ 1.19, MSe ¼ 676.87, p ¼.31, η2 ¼ 03. In order to look at the accuracy of these retrospective recognition estimates, we calculated the difference between the estimated and the actual hit percentages in the recognition test. All three groups showed underconfidence; actual percentage of hits were higher than the estimates by 20%, 15%, and 10% for checker OCD, non-checker OCD, and HC groups, respectively. The apparent difference between the means did not reach significance, F(2, 87) ¼ 1.13, MSe ¼ 655.12, p ¼.33, η2 ¼.03.

3.2.3. False recognition of other lures There were three types of lures other than the critical lures:

4. Discussion

3.2. Recognition 3.2.1. Hit rates A simple measure of recognition performance is the hit rate, i.e., the proportion of target items correctly identified as such by the participants. There was no group effect on the hit rate, F(2, 87) o1 , MSe ¼.051, p ¼ .53, η2 ¼.01.

Table 2. Means and standard deviations for memory and metamemory measures. Checker OCD

Non-checker OCD

M

SD

M

Recall (%) Target Critical Lure

52.44 16.75

17.90 19.79

47.16 16.78

Recognition (%) Target Critical Lure

75.60 19.05a

22.67 14.85

3.24 1.95a 55.96

.51 .49 30.53

Confidence (1–4) Target Critical Lure Recognition estimates (%)

SD

HC M

SD

p

9.41 15.22

53.08 22.26

11.77 23.20

.16 .46

69.27 23.95a

23.89 19.83

73.61 65.00b

20.07 22.04

.53 .00

3.00 1.94a 54.56

.63 .45 27.62

3.15 2.69b 64.10

.53 .51 18.02

.24 .00 .31

Note. Means in the same row that do not share the same superscript are different at p o .01.

To our knowledge, this is the first study addressing false memories in the DRM paradigm in individuals diagnosed with OCD. Groups showed comparable performance in correct recall and recognition. However, both checker and non-checker OCD groups were less prone to false memory. In addition, OCD groups showed lower confidence in falsely recognized items than the HC group. Global recognition estimates also showed comparable accuracy across groups. The most central finding of the present study was the lower false recognition by the two OCD groups compared to the HC group. HC group's false recognition was quite high (65%) and comparable to that found in earlier studies with non-diagnosed groups (e.g., Dodson, & Schacter, 2001; Hanczakowski, & Mazzoni, 2011; McDermott, 1996; Roediger et al., 1995). For the OCD groups, the false recognition rates were less than half that figure (19% and 23%). Equally important was the finding that both OCD groups gave lower confidence ratings for their false recognition decisions. Indeed, this last finding may be taken to suggest better

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metamemory performance in the OCD groups, in the sense of being more attuned to their false memories. As indicated in the introduction section, research findings regarding verbal memory deficit in OCD have been equivocal, with a number of meta-analyses reporting significant but small effect sizes leading Abramovitch and Cooperman (2015) to argue that OCD “… is not associated with meaningful deficits in verbal memory” (p. 28). Our findings are in line with this interpretation; we found no difference in correct recall or recognition. One potential factor here might be that the to-be-remembered material in the present study were semantically related; this might have worked to the benefit of the participants diagnosed with OCD, since they have difficulty organizing information and initiating effective encoding strategies (Buhlmann et al., 2006; Cabrera et al., 2001; Deckersbach et al., 2000). The information that was itself organized around a theme in the DRM task could have facilitated memory encoding. This interpretation is in line with findings reporting no verbal memory differences when the material contains associated items such as the California Verbal Learning Test (e.g., de Geus et al., 2007). What might be leading to substantially lower false memory as well as lower confidence for falsely recognized items by OCD groups? One potential explanation may be that participants with OCD set higher recognition criterion for a “yes” response (Ben Shachar, Lazarov, Goldsmith, Moran, & Dar, 2013; Klumpp et al., 2009). In other words, they need stronger memories (or a stronger subjective sense of remembering) to call an item “old” in a recognition task. Our data, however, do not support this view. A general criterion shift should have affected both the targets and the lures, leading to lower correct as well as false recognition. There was, however, no difference in correct recognition between the groups. A criterion shift account would also predict a similar pattern (decrease) for other types of lures (e.g., unrelated) as well; but that was not the case. Therefore, a criterion shift is not a viable explanation of the data. A second possibility, and the one that we believe explains the pattern of findings more effectively, focuses on processing differences between OCD and HC participants at encoding. Several studies demonstrated that item-based processing reduces false recognition (Arndt, & Reder, 2003; Gunter, Bodner, & Azad, 2007; McCabe, Presmanes, Robertson, & Smith, 2004). For instance, McCabe et al. (2004) showed that when participants were instructed to use item-specific processing vs. relational processing at encoding in a DRM paradigm, there was no difference in correct recognition, but a substantial decrease in false memory in the item-specific processing condition. Such an item-based processing is likely to cause this decline by emphasizing distinctiveness of each individual item and distinctive information is essential for differentiating studied and nonstudied items that are associated in terms of meaning. Although we did not directly manipulate or assess the type of processing in the present study, there is substantial evidence that individuals with OCD have deficits in organizing information and initiating strategic rehearsal, and are more likely to engage in item-specific processing (Buhlmann et al., 2006; Cabrera et al., 2001; Deckersbach et al., 2000; Penades, Catalan, Andres, Salamero, & Gasto, 2005; Savage et al., 2000). As we described above, this tendency for item-based rather than relational processing has a direct effect on false memory rate. The fact that the OCD participants gave lower confidence ratings to the falsely recognized items further supports this explanation. These are also in line with developmental studies of DRM, where a positive relationship was found between semantic processing ability and false memory rates (Brainerd, & Reyna, 2012; Weekes, Hamilton, Oakhill, & Holliday, 2007). Such an explanation based on cognitive processing of OCD participants fit in with the diagnostic monitoring heuristic, which refers to the idea that any processing

that increases the distinctiveness of items in a DRM task lowers false recognition (e.g., Gallo, 2006). In terms of metamemory, OCD participants gave similar confidence ratings to studied items but lower ratings to falsely recognized words. This implies better item-based metamemory accuracy in OCD patients than in HC participants. This pattern can be seen as a natural extension of the processes explained above; distinctiveness affects memory and confidence in the same way. Global estimates of recognition performance showed that OCD groups were neither less confident nor less accurate than HC group in their past performance. Overall, these findings further support the contention that individuals with OCD do not necessarily show a general underconfidence. It also underscores the need to take into account domains of memory (e.g., semantic vs. episodic) as well as the specific nature of the tasks (e.g., verbal, visual etc.) to have a reliable picture of any metacognitive deficits in OCD (Cuttler et al., 2009; Dar, Rish, Hermesh, Taub, & Fux, 2000; Tekcan, Topçuoğlu, & Kaya, 2007). In none of the memory and metamemory measures was there a difference between the checker and non-checker OCD groups. These findings concur with earlier work in memory (e.g., Cuttler et al., 2009; Penades et al., 2005; Tuna et al., 2005) and is, to our knowledge, the first study to show that checker and non-checker OCD groups do not differ in false memory. Therefore, these findings support the suggestion that memory and metamemory issues are not particular to checking symptoms (Cuttler et al., 2009). As noted earlier, literature on OCD-false memory relationship is very sparse. One way of putting the present results into context is to compare them with the only existing work. Our findings regarding false memory can be considered somewhat inconsistent with those of Klumpp et al. (2009), who reported increased false recognition in individuals with obsessive-compulsive (washing) symptoms. Their main finding was that higher false memory by OC participants was limited to recognition decisions for threat-relevant items but not for neutral ones. There are a number of methodological differences that might be important to note. First, we used the standard DRM procedure, whereas Klumpp et al. used a modified version of the procedure. Second, and more importantly, they employed an analogue group of university students who scored high on the washing subscale of the Obsessive Compulsive Inventory (OCI; Foa, Kozak, Salkovskis, Coles, & Amir, 1998). We, on the other hand, employed a well-defined group of participants diagnosed with OCD. This might especially be important with regard to differences in results. Indeed, some findings from the Klumpp et al. (2009) study point to this possibility. They found that the OC group was not different in false recognition from a group who scored low on OCI but matched on depression and anxiety, implying that OC symptoms may not be the main factor in the obtained differences between the OC and control group. Moreover, another study with a clinical OCD group also found a tendency (p ¼.06) for individuals diagnosed with OCD to show lower false recognition errors in a verbal task than control participants (Moritz et al., 2009). These suggest that some aspect of OCD diagnosis may be directly related to lower false memory. Given the paucity of research and the methodological differences between the studies, it is difficult to speculate about the conceptual bases of the differences between two sets of results. In the present study, we used neutral verbal stimuli that were not diagnosis- or threat-relevant. Several researchers showed that the memory differences between OC and control participants are inflated when material is threat-related or when perception of personal responsibility is increased (e.g., Moritz et al., 2007; Radomsky, Rachman, & Hammond, 2001). Our robust findings as well as those of Moritz et al. (2009), who found lower false memory for verbal material in the absence of correct recognition and recall, suggest that false memory may be one memory process where

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differences are obtained regardless of threat-relevance. Effects of the nature of the material seem to represent an important next step for this research. Some potential limitations of the present study should be mentioned. One is that four of the 30 control participants were relatives of the patients. Because OCD has a genetic component, this potential confound should work towards minimizing the difference between the OCD and the control groups in memory measures. However, results showed a robust effect in false memory, indicating that this might not constitute a problem for the present study. Moreover, these four participants were not outliers in terms of their recall or recognition performance within the HC group (z scores ranging between  0.76 and þ0.89). Another potential limitation is that the memory task in the DRM paradigm involves writing down the remembered items. Because of the involvement of two modalities (auditory and graphomotor), this task differs from the typical neuropsychological audio-visual episodic memory tasks. In sum, we showed that checker and non-checker OCD participants were less likely to have false memories compared to control participants and that they showed reliable metacognitive awareness regarding these memories. We suggest that item-based as opposed to relational or deep encoding strategies that are characteristic of individuals with OCD contribute to this pattern of results and require further direct empirical inquiry.

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