Psychological Trauma: Theory, Research, Practice, and Policy 2015, Vol. 7, No. 1, 67–75

© 2014 American Psychological Association 1942-9681/15/$12.00 http://dx.doi.org/10.1037/a0036787

Implicit and Explicit Memory in Survivors of Chronic Interpersonal Violence Reese Minshew and Wendy D’Andrea

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The New School for Social Research We investigated the relationship of implicit and explicit memory to a range of symptoms in a sample of 27 women with exposure to chronic interpersonal violence (IPV). Participants viewed the first 3 letters (“stems”) of trauma-related, general threat, and neutral words; valenced words were matched with neutral words with the same stem. Free recall and a word-stem completion task were used to test explicit and implicit memory, respectively. Participants exhibited increased implicit memory for trauma-related words as compared with both general threat words and neutral “match” words. They also showed increased explicit memory for both general threat and trauma-related words. Finally, although neither implicit nor explicit memory was correlated with PTSD symptoms, implicit memory for trauma-related words was significantly correlated with symptoms associated with ongoing IPV. Interpersonal sensitivity, hostility, and alexithymia were significantly correlated with implicit, but not explicit, memory for trauma words. Somatization, dissociation, and alexithymia were negatively correlated with explicit, but not implicit, memory for general-threat words. These findings suggest that memory processes in survivors of IPV are closely related to the symptom profile associated with complex trauma. Exploring memory processes in survivors of IPV may lend unique insight into the development and maintenance of the symptom profile associated with IPV. Keywords: complex trauma, implicit memory, interpersonal violence

2000). Although the symptom profiles for individuals who have experienced a single traumatic incident frequently share features with the symptom profiles of survivors of ongoing interpersonal violence, the literature suggests a number of important differences, particularly related to self-regulation and interpersonal functioning (e.g., Roth, Newman, Pelcovitz, van der Kolk, & Mandel, 1997). Such symptoms may include difficulties identifying and naming affective states (called alexithymia), depersonalization and fragmentation of internal experience and awareness (called dissociation), high reactivity to interpersonally challenging situations, and paranoid vigilance regarding perceived perceptions of the self by others. Indeed, interpersonal problems and problems with selfregulation may be the cause of as much of the functional impairment in survivors of chronic interpersonal violence as the PTSD symptoms themselves (Cloitre, Miranda, Stovall-McClough & Han, 2005), prompting the addition of these symptoms to the revised definition of PTSD in the DSM5 (APA, 2013). Several cognitive factors, including memory, may undergird these symptoms (van der Kolk, 1994). However, despite the prevalence and clinical significance of exposure to chronic interpersonal violence, the majority of studies that assess the impact of trauma on implicit and explicit memory draw from a sample of participants with PTSD secondary to a single-incident trauma, and focus on the relationship between memory and the traditional symptoms of PTSD. There is evidence to suggest that implicit memory for trauma-relevant material predicts symptoms of PTSD in “traditional” populations (e.g., Ehring & Ehlers, 2011). However, it is unclear whether implicit and explicit memory for trauma-related material correlates with the impaired self-regulation and interpersonal functioning that are hallmarks of multiple violence exposures. The Ehlers and Clark cognitive model of PTSD suggests that the combination of increased implicit and decreased explicit memory for

Cognitive models of posttraumatic stress disorder (PTSD) suggest that particular memory features related to traumatic material are partially responsible for the development and maintenance of the symptoms of PTSD. These models, and specifically the cognitive model developed by Ehlers and Clark (2000), suggest that people with PTSD appear to be more attuned to trauma cues in the environment. The evidence suggests that individuals with PTSD exhibit differences in both implicit (i.e., unconsciously, but not consciously, recalled) and explicit (i.e., conscious or declarative) memories for these cues (for a review, see McNally, 1997). The cognitive model (Ehlers & Clark, 2000) suggests that perceptual priming, a type of implicit memory, for traumatic material is increased in those trauma survivors who develop PTSD. This model also suggests that conceptual priming, a type of explicit memory, for traumatic material will be reduced in trauma survivors with PTSD. However, few studies to date have addressed the relationship between implicit and explicit memory for traumarelated material and the symptoms profile of individuals with PTSD secondary to prolonged interpersonal violence (IPV). The purpose of this study, then, is to explore how implicit and explicit memory processes for affective material are related to the symptoms associated with IPV exposure. The majority of individuals with trauma-related psychopathology have experienced ongoing interpersonal violence (see Kessler,

This article was published Online First June 2, 2014. Reese Minshew and Wendy D’Andrea, Department of Psychology, The New School for Social Research. Correspondence concerning this article should be addressed to Reese Minshew, Department of Psychology, 80 5th Avenue, 6th Floor, New York, NY, 10037. E-mail: [email protected] 67

MINSHEW AND D’ANDREA

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traumatic material is one of the mechanisms of symptom maintenance in PTSD. However, because of the sheer number of situations in which repeated traumatization occurs in survivors of IPV, traumatic memory may generalize to innumerable stimuli. Objectively neutral stimuli may take on a threatening hue, creating a broad range of triggers. In acute trauma exposure, a survivor may have been assaulted in an alley, and develop fears of dark places, of people who look like her perpetrator, and of walking alone. The high frequency of exposure associated with chronic interpersonal violence generates the capacity for associating a large number of neutral cues with threat. For example, a client once described that her perpetrator had assaulted her during all seasons of the year, in all rooms of their house, in their garage, in their yard, at relatives’ homes, and in the car on the way to and from school. Thus the items commonly found in myriad places encountered in daily life and phases of the year created a perpetually overwhelming environment. The process of tagging environmental stimuli as a trauma cue may not differ with increasing exposure frequency, but the sheer number of cues and the ways in which these cues are processed may differ vastly. Moreover, individuals with exposure to ongoing interpersonal violence typically experience not solely repeated, but also early exposure to trauma (see Felitti et al., 1998, for an overview). Memory for early life events is both qualitatively and quantitatively different than memory for events that occur later in life (e.g., Nelson, 1993); early exposure to ongoing trauma also differentially impacts neural structures related to memory (e.g., Bremner & Narayan, 1998). For example, development of the hippocampus, a structure integral to explicit memory (e.g., Rovee-Collier, 1997), occurs during the preschool years. Although trauma-related damage to the hippocampus may not be observable until adulthood, evidence suggests that hippocampal volume in adult survivors of ongoing trauma is significantly reduced as compared with nonexposed controls (see Woon & Hedges, 2008, for a meta-analytic review). Although people exposed to early life trauma may have suboptimal development of explicit memory structures such as the hippocampus, they may still develop implicit memories in the absence of explicit recall (Schacter, 1987). Consistent with Ehlers and Clark’s model, someone who experienced early and ongoing violence may experience two confounding conditions: (a) increased implicit memory for words that have trauma salience and (b) decreased explicit memory for trauma-relevant words.

contribute to PTSD symptom development and maintenance in survivors of trauma. A survivor of an assault, for instance, may not understand what triggered a recent flashback, without realizing that someone near her was wearing the same aftershave as her assailant. In this example, she would have unconsciously oriented to a trauma cue (the aftershave), and experienced involuntary retrieval of the traumatic memory (the flashback). Implicit memory has been tested via both supra- (i.e., above the threshold for conscious recognition) and subliminal (below the threshold for conscious recognition) presentation of cues, followed by a word stem completion task. In a typical word-stem completion task, participants view lists of words, and are then are shown the word stems from the words they have viewed and asked to fill in the rest of the word with the first word that comes to mind. If participants use a word from the previously viewed list to complete the word stem, they are judged to have enhanced implicit memory. A free-recall task can then be administered to test explicit memory. To separate implicit and explicit memory, words that are explicitly remembered are removed from the participant’s list of implicitly remembered words. Several studies have utilized this methodology to explore the possibility of enhanced implicit trauma memory in trauma survivors (e.g., Golier et al., 2002; Lyttle, Dorahy, Hanna & Huntjens, 2010). However, this paradigm has yielded mixed results, leading to the development of a modified version of this task that presents both trauma-relevant words and matched “competing” neutral words (Michael, Ehlers, & Halligan, 2005). This version of the task requires activation of a word that is in matched competition with a word that shares similar stimulus properties; thus, the task is considered more analogous to real-world situations (in which there are innumerable stimuli with similar properties competing for an individual’s attention). For example, participants can be primed with the words “victim” and “vicarious,” and later probed with the stem “vic-”. Michael et al. (2005) found that people with PTSD were more likely than controls to complete word stems with trauma-related words when tested using this competing word paradigm. With a sample of participants who experienced a car accident, Ehring and Ehlers (2011) found that higher implicit memory for accident-related words immediately posttrauma predicted the development of PTSD symptoms six months later, even when adjusting for baseline symptoms.

Implicit Memory

Explicit Memory

Implicit memory is described as memory that impacts an individual without his or her conscious awareness (see Schacter, 1987). According to the Ehlers and Clark cognitive model (Ehlers & Clark, 2000), individual differences in the salience of traumatic cues at the time of the trauma result in differential priming of perceptual cues, privileging traumatic stimuli with a processing advantage. This model posits that individuals with PTSD may orient readily to idiosyncratic trauma cues in the environment, and have difficulty shifting their attention away from these cues. These cues may be activated with extremely brief exposure to cues, or to cues which only partially or tangentially resemble the original stimulus. The heightened perceptual awareness may then trigger memories of the trauma via cue-driven, involuntary retrieval. Thus, according to this model of PTSD, the susceptibility to perceptual priming, or implicit memory, for trauma cues will

The Ehlers and Clark cognitive model of PTSD also posits that trauma survivors with PTSD will evidence decreased explicit memory for traumatic stimuli as compared to survivors without PTSD and nontraumatized controls. Explicit memory, or conceptual priming, consists of memory that has been integrated into the autobiographical memory in an organized fashion. Increased explicit memory for traumatic material competes with stimulusdriven implicit memory for traumatic material. Thus, increased explicit memory for traumatic material can inhibit implicit memory (which facilitates involuntary, cue-driven retrieval) for this material, decreasing the symptoms of PTSD. Though the mechanism for this process is unclear, cognitive neuroscience research suggests that explicit prefrontal processes may serve to either amplify or attenuate more implicit sensory processing (Del Cul, Dehaene, Reyes, Bravo, & Slachevsky, 2009). In the example

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MEMORY AND CHRONIC VIOLENCE EXPOSURE

provided above, for instance, the same woman would be less likely to experience a flashback according to this model if she were consciously aware of the triggering aftershave, and able to verbalize the relationship between her current and past olfactory experience, because sensory material would move from below the threshold of awareness to within it. The detail of the aftershave is thereby incorporated into a conscious narrative of her experience, and this narrative can compete with the involuntary retrieval, allowing her to use conscious cognition to inhibit emotional reactivity, reducing the trigger’s immediacy and impact. Evidence for impaired explicit memory of traumatic material in trauma-survivors with PTSD has been mixed. Using a pairedassociates task, in which participants memorized word pairs and were then probed using one word from the pair, Golier et al. (2002) found that although Holocaust survivors with PTSD had impaired memory overall, they remembered more Holocaust-related word pairs than healthy controls or Holocaust survivors without PTSD. Lyttle and colleagues (2010) found impaired explicit memory for trauma-related words in trauma survivors with PTSD. And, in one of the few studies to investigate memory patterns in survivors of exposure to chronic violence, Cloitre, Cancienne, Brodsky, Dulit, and Perry (1996) found that personality-disordered individuals who had experienced ongoing interpersonal violence exhibited increased explicit memory as compared to personality disordered participants without exposure to interpersonal violence, and healthy controls (Cloitre et al., 1996).

Gaps in the Literature As the symptom constellation in survivors of chronic interpersonal violence is heavily weighted toward symptoms that disrupt self-regulation and interpersonal functioning, the memory impairments associated with PTSD secondary to IPV may load onto these symptoms more heavily than they load on the traditional symptoms of PTSD. In particular, disruptions in the processing and awareness of affect, as manifested in dissociation and alexithymia, may impact memory (DePrince & Freyd, 2004; Meltzer & Nielson, 2010), particularly implicit memory (Lyttle et al., 2010). Additionally, the relationship between implicit and explicit memory of trauma-relevant words and the age of first exposure to trauma has not been explored, despite established developmental differences in the formation of memory. We will first explore implicit and explicit memory for trauma and general threat stimuli in a sample of women with exposure to IV. Then, we will investigate relationships between implicit and explicit memory for general threat, trauma-related, and neutral words and the symptoms of impaired self-regulation and interpersonal functioning, as well as symptoms of PTSD. Finally, we will explore the relationship between implicit and explicit memory and age of first trauma exposure in a complexly traumatized sample.

Hypotheses 1.

Consistent with the cognitive model of PTSD, we will find that trauma-related words will be recalled more than neutral words on measures of implicit, but not explicit, memory in survivors of chronic interpersonal violence.

2.

We predict that implicit, but not explicit, memory for trauma-related and general threat words will correlate

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with symptoms of impaired interpersonal functioning and disturbances of self-regulations in this population. 3.

Ehlers and colleagues (2005) find that PTSD severity is related to implicit, but not explicit, memory for traumarelated words. We predict that implicit memory for trauma-related words will correlate with symptoms of PTSD in survivors of interpersonal violence, but that explicit memory for trauma-related words will not.

4.

Earlier trauma will be correlated with increased implicit, and decreased explicit, memory for trauma-related words.

Method Overview Participants were recruited from the community and participating mental health clinics in Ann Arbor, Michigan, via fliers. Following an initial phone screen, participants who enrolled in the study provided informed consent and completed study questionnaires. Participants completed several physiological and behavioral tasks (see D’Andrea & Pole, 2012, for complete procedure). Participants were then debriefed and compensated. All study activity was approved by the Institutional Review Board at the University of Michigan.

Participants Participants were 27 treatment-seeking women with exposure to interpersonal violence (i.e., childhood physical or sexual abuse, domestic violence). Exclusionary criteria included low levels of English proficiency, involvement in a violent relationship within the last six months, active psychosis, and current pregnancy; however, no participants were excluded. The participants were diverse with respect to age (M ⫽ 38.1, SD ⫽ 13.4), race (74% Euro American; 15% Native American, 7% African American, and 4% Asian American), education (73% had attended or completed college), sexual orientation (20% lesbian or bisexual), and medication status (60% were taking prescribed psychotropic medications).

Procedure Memory task. This task comprised three phases: encoding, implicit memory recall, and explicit memory recall. During the encoding period, participants were told they were participating in an attention task, and that they need not memorize the words that they see. The target words and the matched words (described below) appeared on a computer screen in a fixed random order. Each word appeared for one second, and then disappeared, followed by an “X” that appeared randomly on either the right or left side of the screen. Participants then pressed a button to indicate whether the “X” appeared on the right or left side of the screen. Two practice words were used, followed by two primacy words to control for primacy effects (the primacy effect is the tendency to disproportionately remember the first words in a list). At the end of the battery, two recency words were presented to control for recency effects (the recency effect is the tendency to disproportionately remember the last, or most recent, words in a list).

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During the implicit memory recall phase, participants were presented with word stems that are common to the target and matched words. For instance, if both “threatened” and “theme” had been presented during the encoding period, the word stem “th-” appeared on the screen. The word stem stayed on the screen for 5 seconds, followed by a blank screen. Participants were asked to say the first word that came to mind, and a research assistant wrote their response down. The appearance of the next word stem was triggered by a button press. During the explicit memory recall phase, participants were asked to write down as many of the words that they had seen in the attention/encoding task as they could remember. The three phases of the task took approximately 10 minutes.

Materials Self-report. The Trauma History Questionnaire (THQ; Green, 1996) is a 23-item checklist used to assess the participants’ lifetime exposure to potentially traumatic events (e.g., accidents, sexual assaults, muggings, disasters). This study utilized a 28question revised version (THQ-R). The THQ also assesses age of first and last experience of each event, and the number of exposures to each event. For the purposes of this study, the instrument was reduced to (a) age of first potentially traumatic event, and (b) number of different types of events experienced (e.g., sexual assault plus physical assault ⫽ 2 types). The THQ has shown high test–retest reliability (r ⫽ .70) and strong construct validity (Hooper, Stockton, Krupnick & Green, 2011). The Posttraumatic Stress Disorder Checklist (PCL; Weathers et al., 1993) is a 17-item self-report measure of PTSD symptoms. Participants rated their symptoms over the past month using a 5-point Likert scale, with responses ranging from 1 (not at all) to 5 (extremely). Their responses were summed to yield an overall score. The recommended cutoff for a diagnosis of PTSD with the PCL is 44; at this cutoff, the PCL has a sensitivity of .94 and a specificity of .86 when compared to the diagnostic gold standard, the Clinician-Administered PTSD Scale (CAPS). Internal consistency for the scale is high (Cronbach’s alpha ⫽ .94; Blanchard, Jones-Alexander, Buckley & Forneris, 1996). The Brief Symptom Inventory (BSI; Derogatis & Spencer, 1993) is a 53-item client self-report measure designed to assess common psychiatric symptoms and psychological distress within the last week. The BSI yields nine subscales: somatization, depression, psychoticism, obsession/compulsion, interpersonal sensitivity, anxiety, hostility, phobic anxiety, and paranoid ideation. The subscales are yielded by averaging responses to particular items. Items are scored 1 (not at all) to 5 (extremely). Test–retest reliability of the overall BSI is acceptable to high (r ⫽ .68 –.91) and internal consistency of the subscales is acceptable to high (␣ ⫽ .71–.85; Derogatis & Melisaratos, 1983). For the purposes of this study, we limited analyses to BSI subscales that reflect impairments in interpersonal interactions and in self-regulation. Thus, the interpersonal sensitivity, hostility, paranoia, and somatization indices were used. The Toronto Alexithymia Scale (TAS; Bagby, Taylor, & Parker, 1994) was used to identify difficulty in describing emotion, or tendency to minimize emotion, which may reflect both interpersonal and self-regulatory impairment. The TAS is a 20-item measure with strong test–retest reliability and internal consistency (␣ ⫽ .81). Responses are provided on a 5-point Likert scale, ranging from 1 (strongly disagree) to 5 (strongly agree). This

measure has three-factor loading consistent with the alexithymia construct, and has been assessed for concurrent validity by use of observer rating and behavioral observation (Bagby et al., 1994). The Dissociative Experiences Scale (DES; Carlson et al., 1993) is a 28-item client self-report measure of dissociative experiences including depersonalization, derealization, absorption and amnesia. Participants are asked to rate what percentage of the time they experience various phenomena. A cutoff score of 30 is used to indicate pathological dissociation. Test–retest reliability for the DES ranges from r ⫽ .78 to .96, and ␣ ⫽ .93. Memory-related words. Participants viewed a series of 18 target trauma-related (e.g., violated, abused), 12 target threatrelated (e.g., cancer, bomb), and 12 target neutral words (e.g., wheat, diver) as well as words that matched the stems of the target words. The words were all chosen from a pool of standardized words, and match words were matched for frequency in the English language (Bradley & Lang, 1999). Words appeared in pairs on a computer screen in black ink at a size of 400 ⫻ 600 pixels and at a resolution of 72 dpi. Ratios of the number of primed responses to the number of primed words seen were created to account for the different number of words in each category. Additionally, words that were remembered both explicitly and implicitly were removed from analyses that focused on either implicit or explicit memory exclusively. One outlier was detected for implicit threat and trauma words, and one for explicit threat words. We reran analyses with this outlier excluded, and results were unchanged. Thus, we report on the full sample. Given the small sample size and multiple analyses, we recognize the high probability of Type I error. Therefore, we also report confidence intervals for these analyses, using bootstrapped resampling set to 1000. Results of p ⬍ .1 were reported as marginal only if their confidence interval did not overlap zero, which assures that findings are not spurious given the relatively small sample size (Cobb, 2007).

Results Trauma Exposure Twenty-one of the 27 women (78%) reported nonsexual physical assaults, 18 (67%) reported sexual violence, and 14 (52%) reported both physical and sexual violence. All clients reported that at least one of their assaults was perpetrated by a caregiver or intimate partner. Twenty-one (78%) of the clients also reported experiencing at least one noninterpersonal trauma, such as a lifethreatening accident or natural disaster. All clients had experienced some potentially traumatic event in childhood or adolescence, with the average age of first interpersonal trauma reported as 6.8 (SD ⫽ 5.9) years old. All but one also reported adulthood trauma, with the average age for most recent adult traumatic event occurring at 33.7 years old (SD ⫽ 14.6). Although there is no generally agreed upon cutoff score for chronicity in measuring interpersonal violence on the THQ, all clients had sustained multiple traumatic incidents, multiple types of trauma, and trauma in both childhood and adulthood. This sample reported experiencing between 5 and 25 (M ⫽ 11.2, SD ⫽ 5.6) different types of traumatic events during their life span, such as robbery, rape, and kidnapping. Participants reported that they had experienced, on average, 353 traumatic events between the first and last occurrence of trauma.

MEMORY AND CHRONIC VIOLENCE EXPOSURE

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Self-Report Psychopathology Descriptive statistics summarizing the participants’ selfreported distress are presented in Table 1. As reported in D’Andrea and Pole (2012), participants had significantly more severe distress than comparable outpatient samples on the BSI, PCL, and DES (Ryan, 2007; Ruggiero et al., 2003; Carlson et al., 1993, respectively); they were not significantly different on the TAS (Bagby et al., 1994). All clients had PCL scores above the diagnostic cut score for PTSD. Relationship between symptoms, memory and demographic variables. For implicit memory, age was significantly negatively correlated with implicit recall of neutral words (r ⫽ ⫺.44, p ⫽ .02, CI ⫽ ⫺.73 to ⫺.11]). Education level was not correlated with any implicit memory category. Explicit memory was not related to age. Education level was positively, marginally correlated with explicit recall of general threat words (r ⫽ .45, p ⫽ .02, CI ⫽ ⫺.01 to .76). On the implicit recall task, participants’ primed recall of words was positively correlated with word frequency in the English language for general threat words, and negatively correlated for general threat match, neutral and neutral match words. Implicit recall of trauma words was unrelated to word frequency in the English language. Age and education level were not correlated with PTSD intrusion, avoidance, or hyperarousal symptoms. Age was significantly correlated with interpersonal sensitivity (r ⫽ .51, p ⫽ .01, CI ⫽ .11 to .73). Education level was not correlated with any symptom of self- or relational dysregulation. Hypothesis 1: Trauma-related words will be recalled more than general threat and neutral words on measures of implicit, but not explicit, memory. This hypothesis was partially supported by the evidence. A repeated measures ANOVA indicated a main effect of word valence on implicit recall for target words, F(2.195, 57.074) ⫽ 35.77, p ⬍ .001, ␩p2 ⫽ .579. Planned comparisons revealed that the valence conditions differed significantly, such that trauma words were implicitly recalled most frequently (M ⫽ .20, SD ⫽ .11) followed by general threat words (M ⫽ .11, SD ⫽ .06); p ⫽ .008. The difference between general threat words and neutral words (M ⫽ .05, SD ⫽ .05) was also significant, p ⬍ .001. With respect to explicit recall, there was a main effect of word valence, F(2.313, 60.123) ⫽ 6.03, p ⫽ .003, ␩p2 ⫽ .188. Traumarelated (M ⫽ .04, SD ⫽ .06) and general threat words (M ⫽ .03, SD ⫽ .05) were recalled equally (p ⫽ .722)1 and more than neutral words (M ⫽ .002, SD ⫽ .01). Hypothesis 2: Implicit, but not explicit, memory for traumarelated words will correlate with symptoms of impaired interpersonal functioning and disturbances of self-regulations in survivors of interpersonal violence. All correlations related to implicit memory are presented in Table 2, and explicit memory is in Table 3. This hypothesis was partially supported by the evidence. Implicit memory for trauma-related words was significantly correlated with interpersonal sensitivity, hostility and paranoia as measured by the BSI, and with alexithymia, as measured by the TAS. Implicit memory for trauma-related words was marginally significantly correlated with dissociation, as measured by the DES; the confidence interval for this correlation did not overlap with zero. Implicit memory for trauma-related words was not significantly correlated with somatization as measured by the BSI. Implicit memory for general threat words was not significantly correlated with these symptoms. Implicit memory for neutral words

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was significantly correlated with interpersonal sensitivity; because interpersonal sensitivity was correlated with implicit memory for both trauma and neutral words, we ran a partial correlation between interpersonal sensitivity and implicit memory for trauma controlling for neutral responses; IPS and implicit memory for trauma words were still correlated (r ⫽ .44, p ⫽ .02). Explicit memory for trauma-related words was not significantly associated with interpersonal or self-regulation symptoms. Explicit memory for general threat words was significantly negatively correlated with somatization, dissociation, and alexithymia. Hypothesis 3: Implicit memory for trauma-related words will correlate with symptoms of PTSD, but explicit memory for trauma-related words will not. This hypothesis was not supported by the evidence. Implicit recall was not correlated with PTSD symptoms overall, or with intrusion, avoidance or hyperarousal symptoms for any word valence. Explicit recall of trauma words was not correlated with PTSD symptoms. Hypothesis 4: Earlier abuse will be correlated with increased implicit, and decreased explicit, memory for traumarelated words. This hypothesis was partially supported by the evidence. Implicit recall for general-threat words was negatively correlated with age of trauma onset (r ⫽ ⫺.42, p ⫽ .04; CI ⫽ ⫺.61 to ⫺.02) and marginally correlated with age of trauma onset (r ⫽ ⫺.35, p ⫽ .09, CI ⫽ ⫺.71 to ⫺.01), and there were no significant correlations between the age of trauma onset and explicit memory of trauma or general-threat related words.

Discussion This study explores the relationship between implicit and explicit memory for trauma- and threat-related words and symptoms associated with chronic interpersonal violence. It provides evidence to suggest that the symptoms commonly associated with IPV may be instantiated and maintained by implicit and explicit memory processes. In accordance with the Ehlers and Clark (2000) model, we found that people with exposure to chronic IPV exhibit increased implicit memory for trauma-related material relative to both general threat and neutral words, and they also exhibited more implicit memory for general threat words than for neutral words. Moreover, individuals with exposure to IPV exhibit more explicit memory for both trauma-relevant and general threat words than for neutral words, which is not in alignment with the Ehlers and Clark model of memory. This increased explicit memory for traumarelated material suggests that this material is chronically primed in individuals with exposure to IPV, and that sensitivity to traumarelated information may play a consciously accessible role in the worldview and self-view of these participants. These data suggest that exposure to chronic interpersonal violence may result in both conceptual and perceptual priming for traumatic material. This hypothesis, which we will call the Dual Threat Priming hypothesis, suggests symptoms arising from chronic interpersonal violence may be instantiated and maintained by both implicit and explicit memory patterns. The data further support this view. Implicit memory was correlated with increased interpersonal sen1 We re-ran the repeated measures analysis covarying out the frequency with which the word appears in the English language for recalled words; the results were unchanged, thus we report on the analysis without the covariate of word frequency.

MINSHEW AND D’ANDREA

72 Table 1 Self-Report Psychopathology

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Measure PCLa Intrusion Avoidance Hyperarousal Total BSIb Interpersonal sensitivity Paranoia Hostility Somatization Total TAS totalc DES totald

Current sample mean (SD)

Normative sample mean (SD)

Current sample ␣

14.91 (5.22) 20.91 (5.83) 15.78 (4.64) 51.61 (13.56)

9.2 (4.2) 12.0 (5.7) 8.2 (4.3) 29.4 (12.9)

.827 .763 .671 .899

t (415) t (415) t (415) t (415)

2.92 (0.88) 2.34 (0.75) 1.99 (0.69) 2.18 (0.86) 17.8 (6.32) 55.48 (14.69) 40.7 (18.6)

1.58 (1.05) 1.14 (0.95) 1.16 (0.93) 0.83 (0.79) 11.45 (9.29)

.555 .728 .730 .849 .938 .660 .961

t (1025) t (1025) t (1025) t (1025)

17.7 (16.6)

Difference from norm sample ⫽ ⫽ ⫽ ⫽

6.49ⴱ 7.57ⴱ 8.51ⴱ 8.23ⴱ

⫽ ⫽ ⫽ ⫽

6.32ⴱ 6.27ⴱ 4.43ⴱ 8.42ⴱ

t (48) ⫽ .026 t (846) ⫽ 6.80ⴱ

Note. PCL ⫽ Posttraumatic Stress Disorder Checklist; BSI ⫽ Brief Symptom Inventory; TAS ⫽ Toronto Alexithymia Scale; DES ⫽ Dissociative Experiences Scale. Normed sample for reference: a Ruggiero et al., 2003. b Derogatis & Melisaratos, 1983. c Bagby et al., 1994. d Carlson et al., 1993. ⴱ p ⬍ .001.

matic, sensory memories influence symptoms without conscious awareness of the presence of a memory. This process may be akin to a failure to recognize the salience of trauma cues. Another route may occur through active suppression-based emotional management techniques, whereby coping techniques historically associated with attempts to “ward off” unpleasant emotions are engaged in an active attempt to reduce awareness of emotional responding; here, implicit memories may be the traces of suppressed feelings. Evidence from this study indicates that cue-driven retrieval and the emotionmanagement symptoms are linked, providing further evidence for this interpretation. We predicted that implicit memory for trauma-related words would be correlated with PTSD symptoms in this sample. This prediction was not supported by the evidence. Explicit memory for trauma-related words was correlated positively with intrusive symptoms, which may suggest possible differences in the processing of trauma-related material between individuals who have experienced chronic interpersonal violence versus those who have had single-incident trauma. However, direct testing with a singleincident control group is a necessary next step toward testing this

sitivity, hostility, paranoia, and alexithymia in this sample. These particular symptoms are relevant to impaired ability to develop and maintain interpersonal relationships, suggesting that perhaps people who are prone to such symptoms may be triggered by stimuli outside of their conscious awareness. Additionally, the ability to explicitly remember general threat material was inversely correlated with somatization, dissociation, and alexithymia. This suggests that the ability to bring threatening material into conscious awareness may provide a buffer against difficulties with self-regulation, particularly forms of dysregulation associated with decreased ability to access affect. Although several theories argue that bringing unconscious traumatic material into conscious awareness may reduce the symptoms of PTSD (e.g., Fear Networks, Foa & Kozak, 1986; Dual Representation Theory, Brewin, 2001), these theories have focused on the symptoms of PTSD. This study suggests that being able to consciously access threatening material may be beneficial in other ways. A recent review (D’Andrea, Sharma, Zelechoski, & Spinazzola, 2011) suggests that there may be at least two pathways associated with posttrauma symptoms: one may be cue-driven, implicit retrieval of traumatic memory, whereby auto-

Table 2 Correlations and Confidence Intervals Between Memory for Implicit Words and Symptoms of Exposure to Chronic Interpersonal Violence Implicit memory Trauma

General threat

Symptom

r

p

CI

PTSD (PCL) BSI Interpersonal sensitivity Paranoia Hostility Somatization Dissociation (DES) Alexithymia (TAS)

.26

.25

.46 .58 .55 .20 .34 .47

.02 .01 .01 .35 .09 .02

Neutral

r

p

CI

r

⫺.21 to .67

.11

.65

⫺.34 to .52

.24

.24 to .70 .01 to .82 .15 to .79 ⫺.15 to .52 .01 to .60 .11 to .74

.14 .19 .17 ⫺.05 ⫺.02 .24

.50 .37 .43 .81 .92 .25

.01 to .19 ⫺.16 to .59 ⫺.17 to .49 ⫺.39 to .32 ⫺.42 to .41 ⫺.19 to .71

.62 .14 ⫺.06 ⫺.11 .31 .32

p

CI

.32

⫺.22 to .63

⬍.001 .51 .77 .61 .14 .13

.37 to .79 ⫺.13 to .42 ⫺.37 to .29 ⫺.43 to .25 ⫺.21 to .69 .04 to .55

Note. CI ⫽ confidence interval; PTSD ⫽ posttraumatic stress disorder; PCL ⫽ Posttraumatic Stress Disorder Checklist; BSI ⫽ Brief Symptom Inventory; DES ⫽ Dissociative Experiences Scale; TAS ⫽ Toronto Alexithymia Scale.

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Table 3 Correlations and Confidence Intervals Between Memory for Explicit Words and Symptoms of Exposure to Chronic Interpersonal Violence Explicit memory Trauma

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Symptom PTSD symptoms (PCL) BSI Interpersonal sensitivity Paranoia Hostility Somatization Dissociation (DES) Alexithymia (TAS)

r

General threat

Neutral

p

CI

r

p

CI

r

.05

.82

⫺.59 to .43

⫺.01

.95

⫺.49 to .43

⫺.12 ⫺.03 .05 ⫺.12 ⫺.21 ⫺.32

.56 .88 .82 .55 .33 .12

⫺.49 to .27 ⫺.37 to .22 ⫺.21 to .36 ⫺.38 to .14 ⫺.63 to .46 ⫺.61 to .10

⫺.07 ⫺.32 ⫺.17 ⫺.45 ⫺.51 ⫺.40

.73 .12 .42 .02 .01 .05

⫺.43 to .27 ⫺.58 to ⫺.07 ⫺.42 to .11 ⫺.67 to ⫺.20 ⫺.76 to ⫺.15 ⫺.75 to ⫺.02

p

CI

.24

.31

.16 to .51

.26 .02 .12 ⫺.11 .31 ⫺.01

.22 .94 .55 .59 .13 .94

.17 to .57 ⫺.07 to .20 .04 to .37 ⫺.27 to ⫺.05 .24 to .59 ⫺.15 to .09

Note. CI ⫽ confidence interval; PTSD ⫽ posttraumatic stress disorder; PCL ⫽ Posttraumatic Stress Disorder Checklist; BSI ⫽ Brief Symptom Inventory; DES ⫽ Dissociative Experiences Scale; TAS ⫽ Toronto Alexithymia Scale.

hypothesis. Increased explicit memory for both trauma-related material and general threat material suggests that conscious processes germane to symptom development and maintenance in traumatized samples in a complicated and variable way. On the one hand, greater explicit memory for traumatic words was associated with reduced symptoms. On the other, increased explicit memory was associated with greater intrusion in this sample. These data suggest a complicated picture for which we may only suggest an interpretation. Conscious awareness of traumatic and threat-related stimuli may simultaneously, for instance, reduce somatizing symptoms, while relating to schemas which increase proneness to intrusive memories, such as investment or absorption in narratives of trauma and victimization which keep the trauma at the forefront of one’s identity (Brown, Antonius, Kramer, Root, & Hirst, 2010). Finally, we predicted that earlier experiences of trauma and variety of trauma exposure would be correlated with increased implicit, but not explicit, memory for trauma-related material. The relationship between age and implicit memory is in keeping with the psychoanalytic notion that early events may leave an impact which is difficult to access verbally. Perhaps, because of the developmental nature of language and memory, a word-based paradigm was inappropriate for testing this hypothesis, and a more experiential protocol would be superior.

Limitations and Future Directions This study several weaknesses. First, generalizability is limited by the sample size, the absence of control group, and the homogeneity of the sample in terms of gender, symptom severity, and trauma exposure severity. Replication and expansion of this study with a larger and more variegated sample is a crucial next step. Second, these words, although chosen to be consistent with peer studies, were developed for use with a population with PTSD following single incident interpersonal trauma, rather than PTSD secondary to chronic interpersonal violence, and thus may not capture the full range of cues salient to participants with chronic exposure. Implicit memory may be encoded as a perceptual experience that may or may not be activated by viewing word stimuli. Attention may be another factor that influences both implicit and

explicit memory; in particular, selective and divided attention may differentially impact memory (DePrince & Freyd, 1999). Thus, future work should look at the intersection between memory, attention, and symptoms.

Conclusions Taken together, these findings highlight the role of affective and interpersonal symptoms as particularly salient in consideration of implicit memory; furthermore, implicit memory for affective material appears related to early trauma exposure. The severity of trauma exposure and the manifestation of symptoms in this sample is consistent with the exposure and symptom profile referred to as complex trauma (Herman, 1992). Given the functional impairment associated with complex trauma, as well as the clinical barriers to treating this population, future research should move toward samples with complex exposure profiles.

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Appendix

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Words for the Word-to-Stem Completion Task Word type

Target word

Match word

Stem

Trauma words

Fear Victim Tortured Forced Humiliated Terrified Battered Crushed Pain Weapon Trapped Helpless Abused Afraid Controlled Forced Grabbed Pinned Violated Whore Bomb Tumor Infection Cheated Failure Drowning Mortuary Rejection Cancer Stroke Widowed Diver Matriculate Pertinent Connection Compile Wheat Introduction Proposal Variance Diminish Locomotive

Festival Vicarious Torrent Formal Humanity Terrain Bathed Crust Pack Weasel Trading Helmet Abide Africa Contribution Formal Grapple Pitch Video Which Bowl Tumble Infinite Cheapen Faith Drowsy Mortgage Rejuvenate Canal Stripe Widen Divest Materialistic Personnel Conference Comment Wheel Interval Properly Varsity Diminutive Localization

Fe______ Vic_____ Tor_____ For_____ Hum____ Ter_____ Bat_____ Cru_____ Pa______ Wea____ Tra_____ Hel_____ Ab______ Afr_____ Con_____ For_____ Gra_____ Pi______ Vi______ Wh_____ Bo______ Tum____ Inf______ Che_____ Fai______ Dro_____ Mor_____ Rej______ Can_____ Str______ Wid_____ Di___ Mat_____ Per______ Con_____ Com____ Whe____ Int______ Pro_____ Var_____ Dim____ Loc_____

Threat words

Neutral words

Received June 24, 2013 Revision received February 23, 2014 Accepted March 2, 2014 䡲