Fluent Essays

Adult Eyewitness Memory for Single Versus Repeated Traumatic Events TJEU P.M. THEUNISSEN1* , THOMAS MEYER1,2, AMINA MEMON3 and CAMILLE C. WEINSHEIMER4 1Clinical Psychological Science, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands 2Behavioural Science Institute (BSI), Radboud University Nijmegen, Nijmegen, The Netherlands 3Royal Holloway University of London, Surrey, UK 4Simon Fraser University, Burnaby, Canada Summary: Reports from individuals who have witnessed multiple, similar emotional events may differ from reports from witnesses of only a single event. To test this, we had participants (N = 65) view a video of a road traffic accident. Half of the participants saw two additional (similar) aversive films. Afterwards, participants filled out the Self-Administered Interview on the target film twice with an interval of 1 week. Participants who saw multiple similar films were less accurate in recalling details from the target film than participants in the control condition. On their second report, participants were less complete but more accurate compared with their first report. These results indicate that adults who have witnessed multiple repeated events may appear less reliable in their reports than adults who have witnessed a single event. These findings are relevant when evaluating eyewitness evidence and call for new approaches to questioning witnesses about repeated events. Copyright © 2017 John Wiley & Sons, Ltd. INTRODUCTION It is well established that eyewitness memory can be unreli- able and lack specific details under certain circumstances, especially when the witnessed events are emotional (for a review, see Fulero, 2012). This can have dramatic conse- quences, including misled or inaccurate crime investigations. Moreover, the amount of detail and specificity with which a witness recalls an event is often crucial in decisions about the reliability and credibility of the witness. For example, UK Home Office decision-makers are led to expect that the pres- ence of specific details in witness statements signals credibil- ity and can assist in determining refugee status (UK Home Office, 2015). Therefore, research into factors that determine eyewitness reliability is a priority. An explanatory framework for this line of research is pro- vided by fuzzy trace theory (FTT). It posits that humans can encode and retrieve information at multiple specificity levels and distinguishes two types of mental representations, or memory traces, of a past event. Accordingly, verbatim traces are detailed representations of specific information, whereas the gist trace lacks specific detail, is based on category and meaning and is therefore inexact (Brainerd & Reyna, 2002; Koutstaal & Cavandish, 2006). FTT states that verbatim and gist information is processed, stored in memory, and retrieved in a dissociated parallel fashion. As a result, gist and verbatim traces may be available and prone to situational influences to different degrees (Brainerd & Reyna, 2002). People differ in the level of specificity with which informa- tion is processed and stored, and hence in the type of trace that is more available for retrieval (Koutstaal & Cavandish, 2006). For eyewitness reports, this implies that the type of trace that is available and being accessed determines the level of detail (Wolfe, Reyna, & Brainerd, 2005). Several factors may influence the availability and access of gist and verbatim traces. For instance, over time, verbatim traces are reduced in strength, and hence, specific details of the event and the surrounding context become less accessi- ble, as compared with gist traces (e.g., Murphy & Shapiro, 1994; Reyna & Brainerd, 1995). Interference is one factor that accounts for reduced accessibility of verbatim traces (e.g., Brainerd, Howe, & Reyna, 1996; Payne, Elie, Black- well, & Neuschatz, 1996). An important source of interfer- ence that may modulate the availability of gist versus verbatim traces is exposure to later events that are similar to the target event. Such repeated similar events can be defined as ‘a series of events that are conceptually linked and provide expectations about future similar encounters.’ Indeed, several studies have demonstrated that the retrieval of verbatim memories is facilitated when the content of an event matches the verbatim information of earlier experi- ences (e.g., Reyna & Lloyd, 1997). Similarly, gist memories of an event are more likely to be accessed when its semantic content (e.g., the underlying meaning) matches with other past experiences (e.g., Wolfe et al., 2005). Thus, repeated similar experiences that differ in verbatim information may strengthen gist traces in memory, while verbatim traces become less available. It follows from this that witnesses of repeated similar events might be less reliable than witnesses of single events, as reflected in lower accuracy, completeness and consistency (see Smeets, Candel, & Merckelbach, 2004). For instance, increased reliance on gist traces might undermine their reporting accuracy, which refers to the proportion of cor- rectly stated information and incorrect information such as distortions (i.e., a major detail change of an existing element) and commission errors (i.e., introduction of a completely new element; Gudjonsson & Clare, 1995). Moreover, the com- pleteness of recall, that is, the total amount of information reported, may be compromised by omission errors. Finally, witnesses of repeated events might provide less consistent re- ports across multiple recall sessions. Assuming there is interference from recall of similar events, the details that are provided about a single event may change across repeated in- terviews (i.e., there may be omission errors or contradictions in the details reported across different interviews; Smeets, Candel, & Merckelbach, 2004). *Correspondence to: Tjeu Theunissen, Department of Clinical Psychology, Maastricht University, Maastricht, The Netherlands. E-mail: [email protected] Copyright © 2017 John Wiley & Sons, Ltd. Applied Cognitive Psychology, Appl. Cognit. Psychol. 31: 164–174 (2017) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/acp.3314 http://orcid.org/0000-0003-1393-0058 In child witnesses, several studies have looked at recall of repeated events and found that memory for repeated similar events was characterized by stronger reliance on gist repre- sentations compared with incident-specific recall. Brubacher, Roberts, and Powell (2012) asked children (aged 4–8 years) to recall a single-play activity session or four play sessions that took place over a 2-week period. They found an age- related increase in generic references when children were questioned about the repeated sessions. In line with this lab- oratory research, a study among victims of childhood sexual abuse found that those who had suffered repeated abuse reported fewer episodic (instance specific) details and more general information compared with victims of a single abu- sive event (Schneider, Price, Roberts, & Hedrick, 2011). Moreover, source misattributions frequently occur when children recount multiple occurrences of an event (Connolly & Price 2006; Powell & Thomson, 1996). Connolly, Price, Lavoie, and Gordon (2008) had participants watch video recordings of children describing the same event and rated the children’s credibility. For half of the children, the event had been experienced once, and for the other half, the event was last in a series of similar events. Although all children were similarly accurate, repeated-event children were judged to be less credible than the single-event children. An analysis of the content of the reports revealed that most of the vari- ability in credibility ratings could be attributed to differences in consistency between single-event and repeated-event reports. To summarize so far, a review of theory and research with child witnesses leads us to expect recall of repeated events to rely on a general event representation in line with FTT. However, almost all the relevant work is limited to a small number of studies of children. We simply do not know enough about memory for repeated events in adults to draw the same conclusions with confidence. With the aim of examining the effects of witnessing single versus repeated events on eyewitness memory, we exposed healthy adult participants to a target film of a devastating car crash and had them fill out a Self-Administered Interview (SAI; Gabbert, Hope, & Fisher, 2009) on details of the film in two separate sessions. Crucially, in one group, the target film was preceded by neutral unrelated films (single-event condition), whereas in another group, the target film was pre- ceded by similar shocking films (repeated-event condition). To assess the reliability of the testimonies, we focused on report accuracy, completeness, and consistency (Smeets, Candel, & Merckelbach, 2004). Drawing on FTT, we expected participants in the repeated-event condition to provide less reliable testimonies, as indicated by poorer accuracy, completeness, and consistency across two reporting sessions. In addition, we expected participants to be less com- plete in their second report session compared with their first report session. METHOD Design Participants were randomly assigned to one of two conditions. The experimental design is shown in Table 1. The between-subjects variable was condition (single, repeated events) and the within-subjects variable was time (report session one, two). The dependent variables were report accuracy, completeness, and inconsistency, which were measured over the two repeated test sessions during which eyewitnesses answered questions about the witnessed event(s). Participants Sixty-five adult students (51 women) within the age range of 18–35 years (M = 19.5, SD = 2.58) were recruited from Royal Holloway University of London. Participants were randomly assigned to the single-event (n = 32) or repeated- event condition (n = 33). As an inclusion criterion, all partic- ipants were required to be proficient English speakers. The exclusion criteria were current psychological or psychiatric problems, a history of traumatic experiences (including severe road accidents), fear of seeing blood, and pregnancy. To establish the inclusion and exclusion criteria, we relied on the participants’ self-report. For this study, participants could earn study credits or enter a lottery to win a £25 Amazon voucher. This study was reviewed and approved by the Psy- chology Department ethics committee at Royal Holloway University of London. Material Films To resemble real-life eyewitness memory, we used the stressful film paradigm (Lazarus, Opton, Nomikos, & Rankin, 1965) in which participants watch trauma film segments. The trauma films contained footage of the aftermath of road traffic accidents, which displayed graphic horrific images such as injuries, dead bodies, and victims in distress. Duration lengths of all films in this study were approximately 2 minutes 43 seconds. The target film consisted of staged footage of the aftermath of a severe multiple car crash involving eight victims. Among the victims were three female students, two of whom died while one was severely injured. Two drivers of other cars died Table 1. Design Session Time delay Single-event condition Repeated-event condition 1 Neutral film Trauma film 2 Three successive days Neutral film Trauma film 3 Target trauma film Target trauma film 4 5–9 days after session 3 First report session First report session 5 6–8 days after session 4 Second report session Second report session Single Vs. Repeated Traumatic Events 165 Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017) before they could be taken to hospital. Two young children sat in the backseat and were physically unharmed but in shock. Some of the displayed scenes were graphic and shown in full detail. This film was well suited for the purpose of this study, as it was rich in distinctive features such as multiple victims of varying age, rescue helicopters and short dialogues. Prior studies have successfully used this material to induce negative affect (NA) and aversive memories (Meyer et al., 2014; Meyer et al., 2013). In the repeated-event condition, two additional aversive films were shown before the target film. These films were two compilations of real-life footage from the aftermath of road traffic accidents that have been used by Steil (1996) and others (e.g., Brewin & Saunders, 2001; Holmes, Brewin, & Hennessy, 2004). The films were chosen such that their content closely matched with each other (i.e., depicting corpses and injuries, victims in distress and emergency ser- vice personnel working to extract trapped victims), and their graphic aversive details were shown in a similar fashion. They, therefore, well fitted our definition of repeated events. In the single-event condition, two neutral, unrelated films were shown to participants prior to the target film. Both consisted of fragments from a documentary about glass blowing. Because of ethical concerns related to the emotion- ally provoking material shown to participants, we encour- aged participants to contact the experimenter or student counselling at Royal Holloway at any stage during the study if they experienced any distress. However, no participant reported ongoing distress to the experimenter. Any contact of the participants to the counselling services after the study was treated as confidential and therefore could not be ascertained. The Self-Administered Interview The SAI (Gabbert, Hope, & Fisher, 2009) is a recall tool used for the acquisition of eyewitness reports from different types of crime. It arose out of the Cognitive Interview, which is a memory-based procedure designed to maximize the amount of recalled information through engagement in effec- tive search and retrieval processes (Fisher & Geiselman, 1992; Memon, Meissner, & Fraser, 2010). The original SAI contains seven sections of information and instructions aimed to facilitate the self-report and recall of the witnessed event and has been shown to efficiently and effectively elicit detailed and accurate accounts of a witnessed event (Gabbert, Hope, & Fisher, 2009). For this study, we used a modified computer-administered version of the SAI that contained a mental context reinstatement section, followed by four report sections. The first report section required participants to report everything they could remember about the event and the people that were involved. In the next three report sections, participants were asked to report on the appearance of the people, vehicles, and distinctive objects that were observed in the event, respectively. This included estimating the number of people involved in the accident, vehicles and objects, before describing each in detail. The Depression Anxiety Stress Scales 21 The 21-item version of the Depression Anxiety Stress Scales (DASS-21; Lovibond & Lovibond, 1995) is a brief self-report questionnaire consisting of three 7-item scales that assess depression, anxiety, and stress, respectively. Each item reflects a short statement on which participants have to indicate how it applied to them over the past week using a 4-point scale (1 = did not apply to me at all; 4 = applied to me very much, or most of the time). To derive a DASS-21 total score, we summed all items (α = .87) and multiplied the result by 2, making the scores comparable with those of the longer 42-item version. We used the total score to check for baseline differences between conditions in general psychological distress (Henry & Crawford, 2005). The Positive and Negative Affect Schedule The Positive and Negative Affect Schedule, state version (PANAS; Watson, Clark, & Tellegen, 1988) is a short self- report questionnaire that measures two dimensions of mood, namely, positive affect and NA, on two 10-item subscales. Each item describes a feeling or emotion, and participants have to rate the extent that the item applies to them in that moment. Answer options range from 1 (very slightly or not at all) to 5 (very much). In this study, we used the NA subscale (all αs > .84) to measure affective responses to viewing the stimulus films. Procedure Participants were invited to five individual sessions. The first three sessions took place in a sound-attenuated testing room on three successive days. At first, participants gave informed consent and filled out the DASS-21. In the first three sessions, they viewed the assigned films (Table 1) and filled out a PANAS before and directly afterwards. All films were displayed on computer screens. Participants used head- phones to avoid distraction caused by background noise, and to increase immersion in the shown films. The fourth session took place within a period of 5 to 9 days after the third session. The length of this period was established to increase ecological validity. In this session, participants filled out the modified SAI on the laboratory computer. Detailed instructions were provided on the computer screen, and participants were asked to spend at least 25 minutes for the first report section of the SAI. Before reporting, the experimenter ensured that participants understood the instructions. After a delay of 6 to 8 days, the fifth session took place. In this session, participants reported on the target film for a second time by filling out an identical SAI to the one they were given the first time. This SAI was completed digitally at home with the same instructions. Last, partici- pants were debriefed, thanked, and compensated for their participation. Coding Two independent coders viewed the target film and coded as many units of information (UOIs) as they could observe. UOIs were defined as sentences and parts of information that are independent of all other information units. For example, ‘the woman with long blond hair’ consists of three indepen- dent UOIs, namely, ‘woman,’ ‘long hair,’ and ‘blond hair.’ The coders evaluated each other’s UOIs by indicating agree- ment or disagreement. Because each coder had to evaluate a 166 T. P. M. Theunissen et al. Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017) different list constructed by the other coder, inter-rater agreement ratios (number of agreements/number of agree- ments + disagreements) rather than kappa were used to assess reliability, revealing satisfactory agreement ratios of 0.94 and 0.83. A coding sheet was then constructed, which included all UOIs that the coders had agreed on. In total, 683 UOIs were included, divided over the following sections: General (27), Actions (78), People (431), Vehicles (108) and Objects (39). For every participant, we added all additional UOIs that they reported to this list. Next, all par- ticipants’ reports were scored for reported UOIs and coded for correctness, distortion, and commission. This was carried out by one coder, using a coding manual and the constructed coding sheet (Appendix A). A score of 1 was given if units were correctly reported, and a score of 0 was given if not. The same scoring allocation was applied for the distortion and commission variables. An accuracy index was also calculated for each participant by dividing the number of correctly reported details by the sum of correct details, distortions, and commissions. Completeness was calculated by summing all reported UOIs. Inconsistency was calculated by comparing each partici- pants’ first and second accounts with each other. This was performed by summing direct discrepancies, the number of additions, and the number of omissions in the second report, relative to the first report, yielding an inconsistency score. In addition, 20\% (n = 28) of the participants’ reports were coded by the second coder to assess inter-coder reliability. For accuracy, inter-coder reliability was calculated by averaging the ratio between agreement and disagreement per participant over all 28 reports and information categories. For completeness and inconsistency, each coder’s complete- ness and inconsistency scores were standardized across participants with a z-transformation. Absolute differences between the two z-scores of each participant were then averaged over all participants. This yielded inter-coder disagreements for accuracy, completeness, and inconsistency of 0.17, 0.17, and 0.25, respectively. Statistical analyses For our main analyses on accuracy, completeness, and inconsistency scores, we performed 2 (report session: first, second) × 2 (condition: single-event, repeated-event) mixed-design analyses of variance (ANOVAs). Main and interaction effects were then tested by means of t-tests. Similarly, the analyses of baseline group differences and mood responses relied on ANOVAs and t-tests. Time interval variations between sessions three and four, four and five, and three and five were included in the analysis as covariates. For all tests, a p-value < .05 (two-tailed) was considered to be statistically significant. RESULTS Group differences at baseline An independent samples t-test revealed no significant difference of age between conditions, t(63) = 1.313, p = .197. A chi-squared test revealed no significant differences in the distribution of sex between conditions, χ2(1, N = 65) = 1.618, p = .20. For all participants, total DASS-21 scores were within the normal non-clinical range (M = 17.38, SD = 12.91; Henry & Crawford, 2005). An independent samples t-test revealed no significant difference of DASS-21 scores between conditions, t(63) = 1.480, p = .14. Mood responses to films A 3 (film session: first, second, third) × 2 (time: pre-film, post-film) × 2 (condition: single-event, repeated-event) mixed-design ANOVA on PANAS-NA scores revealed a significant three-way interaction, F(2, 62) = 6.615, p < .01, ηp2 = 0.176. Paired samples t-tests revealed that PANAS- NA scores increased from pre-film to post-film for the repeated-event condition in the first, t(33) = 5.34, p < .001, second, t = 4.64, p < .001, and third sessions, t = 5.69, p < .001. Meanwhile, for the single-event condition, PANAS-NA increased significantly only in the third (target film) session, t(32) = 6.24, p < .001, but not in the first two sessions, ps > .26. In the third session, the difference score from pre-film to post-film PANAS-NA did not differ between the two conditions, t(63) = �0.424, p = .67.1 In the third session, PANAS-NA post-film scores between the single-event condition and the repeated-event condition did not differ significantly. Reliability indicators In Figure 1, accuracy and completeness results are displayed for the single-event condition and the repeated-event condi- tion over the two report sessions. A 2 (report session: first, second) × 2 (condition: single-event, repeated-event) mixed-design ANOVA on accuracy scores revealed a main effect of condition, F(1, 54) = 36.52, p < .001, ηp2 = 0.403, with significantly higher accuracy in the single-event condi- tion than in the repeated-event condition.2 In addition, a main effect of report session was revealed, F(1, 54) = 6.37, p = .015,ηp2 = 0.106, with more accurate reports in the second compared with the first report session.3 There also was a trend-significant interaction between condition and report session, F(1, 54) = 3.97, p = .051, ηp2 = 0.069. Paired samples t-tests showed that this was a result of a significant increase in accuracy between the two report sessions for the 1 DASS-21 scores at baseline and PANAS-NA increase in session 3 did not correlate with accuracy and inconsistency scores (all Pearson’s r < .21, p > .101). Only completeness in the second reporting session correlated negatively with NA increase, r = �.29, p = .029. However, including PANAS-NA increase as a covariate did not substantially change the results or alter the conclusions in the following analyses on completeness. 2 Separate analyses for each of the accuracy parameters revealed that signif- icantly more correct details, F(1, 54) = 9.294, p < .01, ηp2 = 0.147, and fewer commissions, F(1, 54) = 25.14, p < .001, ηp2 = 0.318, were reported on the target film in the single-event condition, compared with the repeated-event condition. 3 Significantly fewer correct details, F(1, 54) = 69.71, p < .001, ηp2 = 0.564, fewer distortions F(1, 54) = 25.04, p < .001, ηp2 = 0.317, and fewer commis- sions, F(1, 54) = 12.676, p ≤ 01, ηp2 = 0.190, were reported on the target film in the second compared with the first report session. As overall accuracy in- creased across sessions, these findings indicate that the number of correctly reported details decreased proportionally less than the number of distortions and commissions. Single Vs. Repeated Traumatic Events 167 Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017) repeated-event condition, t(26) = �2.56, p = .017, which was not found for the single-event condition, t(28) = �0.52, p = .61. For completeness and inconsistency, the predicted main effects of condition were not significant, all Fs < 63, ps > .43. There also were no interaction effects, all Fs < 0.27, ps > .61. For completeness, the mixed-design ANOVA only revealed a main effect of report session, F(1, 54) = 63.09, p < .001, ηp2 = 0.539. Participants in both conditions pro- duced less complete reports on the target film in the second compared with those in the first report session. Time interval as a covariate did not lead to any differences in our results. All other main effects and interactions were non-significant and/or irrelevant to our hypotheses, all F ≤ 0.624, p ≥ .433, ηp2 ≤ 0.011. DISCUSSION This study investigated whether there are differences in accuracy, completeness, and inconsistency in adults who have witnessed similar, repeated traumatic events compared with adults who have witnessed only one traumatic event. We found that adults who are shown multiple films of traumatic scenes from a car accident were less accurate in their reports compared with participants who saw a neutral film. In addition, the reports in both conditions were less complete, yet more accurate, in their second report session than in their first report session. This increase in accuracy (mainly driven by decreases in distortions and commissions) was more pronounced in the repeated-event condition. These results suggest that adults who have witnessed repeated, similar traumatic events are less accurate, and thus potentially less reliable witnesses, than adults who have only witnessed a single traumatic event. These results fit with our expectations. That is, FTT would predict that participants in the repeated-event condition would rely more on (erroneous) gist traces that are based on similar experiences, and less on verbatim traces from the target film, leading to less accurate reports (Wolfe et al., 2005; Reyna & Brainerd, 1995; Schneider et al., 2011). Contrary to expectation, there were no differences between groups in completeness and inconsistency, suggest- ing that the effects of exposure to repeated negative events are limited to report accuracy. To our knowledge, the present study is the first to explore the impact of repeated emotional experiences on memory completeness and consistency in adults. In children, prior studies on non-emotional memory found either no effects or lower consistency for multiple similar events compared with a single event (Connolly et al., 2008; Schneider et al., 2011). However, unlike the free-report method we used, these authors tested memory for specific, non-emotional details using cued recall. Thus, it remains to be determined whether these differences can be attributed to the effects of age, reporting method, and/or emotionality of the memories. The reduced completeness of reports in the second session compared with the first was likely due to forgetting over time (Wixted & Ebbesen, 1991; but see Campbell, Nadel, Duke, & Ryan, 2011). Consistent with this observation, the SAI has been shown to boost detail memory initially, followed by a drop in the number of correct details within a 1-week interval (Krix, Sauerland, Gabbert, & Hope, 2014). The difference in completeness between the two report sessions could also be explained by motivational differences. During the second (home) report session, participants did not have an experimenter present to ensure participants continued typing until they reached the instructed minimum typing time. We were also unable to control for distractions that may have occurred during the at-home report session; consequently, the at-home session may have differed from the lab-based session (e.g., Barenboym, Wurm, & Cano, 2010). Hence, motivational differences might explain a shift in criterion, leading to less complete, yet more accurate reports at session 2. This explanation would reconcile our results with prior findings suggesting that false memories (of words) are stable over time (e.g., Toglia, 1999), whereas here we found decreases in distortions and commissions between the sessions. One advantage of our design was that report session was a within-subjects variable and both single- film and repeated-event conditions …