Adult Eyewitness Memory for Single Versus Repeated Traumatic Events

TJEU P.M. THEUNISSEN1
* , THOMAS MEYER1,2, AMINA MEMON3 and
CAMILLE C. WEINSHEIMER4
1
Clinical Psychological Science, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
2
Behavioural Science Institute (BSI), Radboud University Nijmegen, Nijmegen, The Netherlands
3
Royal Holloway University of London, Surrey, UK
4
Simon 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 unreliable and lack specific details under certain circumstances,
especially when the witnessed events are emotional (for a
review, see Fulero, 2012). This can have dramatic consequences, 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 presence of specific details in witness statements signals credibility 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 provided 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 information 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 accessible, 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, Blackwell, & Neuschatz, 1996). An important source of interference 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 experiences (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 correctly 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 completeness 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 reports 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 interviews (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
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 representations 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 agerelated increase in generic references when children were
questioned about the repeated sessions. In line with this laboratory 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 abusive 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 variability 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 preceded 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 complete 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 repeatedevent condition (n = 33). As an inclusion criterion, all participants 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 Psychology 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 service 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 emotionally provoking material shown to participants, we encouraged 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 effective 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 selfreport 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 headphones 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, participants 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 independent UOIs, namely, ‘woman,’ ‘long hair,’ and ‘blond hair.’
The coders evaluated each other’s UOIs by indicating agreement 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 agreements + 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 participants’ 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 participants’ 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 completeness 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
A3(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,
ηp
2 = 0.176. Paired samples t-tests revealed that PANASNA 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 condition 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, ηp
2 = 0.403,
with significantly higher accuracy in the single-event condition than in the repeated-event condition.2 In addition, a
main effect of report session was revealed, F(1, 54) = 6.37,
p = .015, ηp
2 = 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, η
p
2 = 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 significantly more correct details, F(1, 54) = 9.294, p < .01, ηp
2 = 0.147, and fewer
commissions, F(1, 54) = 25.14, p < .001, η
p
2 = 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, η
p
2 = 0.564,
fewer distortions F(1, 54) = 25.04, p < .001, η
p
2 = 0.317, and fewer commissions, F(1, 54) = 12.676, p ≤ 01, ηp
2 = 0.190, were reported on the target film
in the second compared with the first report session. As overall accuracy increased 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, η
p
2 = 0.539. Participants in both conditions produced 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,
ηp
2 ≤ 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, suggesting 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 singlefilm and repeated-event conditions completed the second
session at home, thereby providing a useful estimation of
how SAI reports compared at the two time points in terms
of accuracy and completeness. However, further investigation is needed to shed light on the complex relationship
between testing environment, repeated testing, and changes
in the quality of memory reports over time.
Figure 1. Mean accuracy and completeness values for the singleevent condition and the repeated-event condition across the two
report sessions. The single-event condition displayed higher
accuracy scores than the repeated-event condition in both report
sessions. A trend-level interaction (p = .051) suggests that accuracy
increases over time, but only in the repeated event condition. Mean
completeness values were significantly lower in the second report
session than in the first report session, irrespective of condition.
Error bars indicate standard error of the means
168 T. P. M. Theunissen et al.
Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017)
As intended, the trauma films successfully induced negative emotional states, as evidenced by significant increases
in PANAS-NA scores following the aversive (but not the
neutral) films. Importantly, NA scores increased similarly
in both conditions in response to the target film, which indicates that our findings cannot be attributed to differential
emotional impact of the target film in both conditions. Still,
one might argue that participants in the repeated-event
condition perceived more emotional stress at memory
retrieval than participants in the single-event condition
during the report sessions, elicited by the semantic links with
the other traumatic video memories. This might have led to
differences in recall performance between the conditions.
However, a recent study showed that stress does not influence recall performance when using the SAI as the recall tool
(Krix et al., 2016). These findings suggest that emotional impact is perhaps not an alternative explanation for the difference found in accuracy results between the conditions.
Moreover, this view is in line with the finding that the
increases in NA scores in response to the target film were
not related to accuracy, completeness, or inconsistency
outcomes.
The results obtained here suggest that adults who have
witnessed several similar traumatic events are less accurate
in their testimony than adults who have witnessed a single
traumatic event. This can have major consequences in a legal
setting and other contexts. Be it a criminal case or an interview to assess the credibility of an asylum claim, a witness
is expected to recall unique details pertaining to a specific
episode (Connolly & Price, 2013; Connolly & Read, 2006;
Home Office, 2015). Therefore, our results suggest that we
need to develop and test ways to increase accuracy in the
reports of adult eyewitnesses who have witnessed repeated
events. This could eventually contribute to the development
of new witness interviewing strategies that improve the
identification of episodic details of one target event among
a series of similar events. Assuming FTT’s prediction that
in repeated similar events, gist traces become more accessible than verbatim traces, interviews directed at retrieving
episodic (verbatim) details may benefit if generic prompts
are avoided. Instead, the focus should be on episodic
prompts that help cue distinctive details of a particular
instance (also Brubacher et al., 2011). This may help
witnesses correctly attribute their memories to the corresponding events and to identify unique details pertaining to
an instance of a given event. Our findings also warn that a
more careful approach may be needed in interpreting witness
reliability and credibility when there is a history of the
witness or victim being party to other similar events. The
expectations as to what we can expect from eyewitnesses
in these situations should be adjusted. For example, the
UK’s asylum policy instructions (UK Home Office, 2015)
should be amended to make reference to reports based on
repeated event experiences.
The practical significance of obtaining data on adult
memory for repeated event experiences is important for
several reasons. One of the biggest challenges facing our
legal system today concerns the reliability of testimony
given by complainants about repeated events in circumstances where no corroboration is available. For example,
in seeking legal protection, asylum seekers who are often
the victims or witnesses of multiple and repeated atrocities
have to explain why they cannot stay in their country in line
with the Geneva Convention relating to the status of refugees
(United Nations, 1951). Being able to give a credible
account of repeated experiences is also of crucial importance
to victims of sexual trafficking. Trafficking cases typically
involve multiple instances of abuse and rape that may cover
years (Lehti & Aromaa, 2006; OSCE, 2013). There is ample
evidence that asylum caseworkers and judges are influenced
by the consistency of accounts provided (Herlihy et al.,
2012; UNHCR, 2013). Hence, it is critical that we understand what effect witnessing repeated events has on memory
accuracy, completeness, and consistency.
This study contributes to the understanding of human
memory and provides insight about factors that can influence
eyewitness memory and testimonial performance. Few studies have focused on the effect of having experienced a series
of related, similar events on memory, and to date, relevant
research has only been conducted on child witnesses. Future
research needs to establish whether our findings are specific
to emotionally arousing negative events or whether they
apply to other types of arousing events including positive
experiences. Moreover, research is needed to disentangle
whether our findings can be attributed solely to viewing
semantically related materials, or whether they can also be
explained by repeated exposure events that induce negative
mood. There is some evidence to suggest negative emotion
conveys focal benefits on memory for detail, although this
does not mean all event details will be accurately remembered (Steinmetz & Kensinger, 2013). Research has also
shown that the types of encoding processes relating to memory (e.g., perceptual versus elaborative processing) can differ
based on the affective qualities of the emotional information
(Steinmetz & Kensinger, 2013), as well as the reactions of
individuals to such events (Herlihy et al., 2012). Moreover,
future studies are needed to establish whether the changes
in completeness are solely due to the passage of time and
whether the retrieval environment and questioning technique
can improve reports of memory for repeated events.
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APPENDIX A
Coding Manual
Department of Psychology, Eyewitness Research Group.
http://www.pc.rhul.ac.uk/sites/rheg/
Eyewitness Memory for Single Versus Repeated
Traumatic Events
Coding Manual
Primary Goals:
1. To examine differences between reports from adults who
have been subjected to witness repeated events and
reports from adults who have been subjected to a single
event in accuracy, completeness and consistency.
170 T. P. M. Theunissen et al.
Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017)
2. Check for possible external intrusions in the repeated
event condition.
Coding Instructions.
You have received 7 files attached in an email:
• ‘Coding Manual’ (which is this one)This manual includes
all instructions for coding and processing participants’
data.
• ‘Participants reports’This document includes the reports
of participants you will be coding.
• ‘CODING TEMPLATE’This Excel file is the template
you will use for coding the participants’ reports.
• ‘OUTPUT EXCEL’This Excel file is the output file in
which you will copy the results for every single
participant.
• ‘VIDEO 1 Aftermath + headsurgery.mp4’This is a
video you will use for coding for possible intrusions from
video 1 (v1).
• ‘VIDEO 2 Aftermath + wounded knee + moving
bodies.mp4’This is a video you will use for coding for
possible intrusions from video 2 (v2).
• ‘TARGET VIDEO.wmv’This is the video you will use
for coding ‘Accuracy’, ‘Distortions’, ‘Commissions’
and.‘Discrepancies’. These terms will be explained later on.
In this study, all participants had to report their memory
twice of a watched video, namely, ‘TARGET VIDEO.
wmv’. From now on, this video will be referred to as the
‘target video’. Half of the participants watched two other
videos beforehand watching the target video, namely,
‘VIDEO 1 Aftermath + headsurgery.mp4’ and ‘VIDEO
2 Aftermath + wounded knee + moving bodies’. From
now on, these videos will be referred to as ‘video 1’ and
‘video 2’.
The coders’ task is to code for ‘Accuracy’, ‘Distortions’,
‘Commissions’ and ‘Discrepancies’ of both the participants’
reports. In addition, the coder will check for possible incorrect reported information that could be an external intrusion
elicited by video 1 or video 2.
A coding template (‘CODING TEMPLATE’) was
created, which includes lists of units of information that
already have been identified as correctly occurring in the
target video. When coding for Accuracy, Distortions,
Commissions and Discrepancies, these lists of units of
information are of help when deciding whether a reported
unit did or did not occur in the target video.
STEP 1
First, watch the three video clips and read their descriptions (Appendix A) carefully and multiple times. You
already are familiar with the ‘TARGET VIDEO’. The
content of the TARGET VIDEO is most important as all
participants reported on the target video. This target video
is then the source on which you have to base your judgement on when coding the reported information. All videos
are approximately 2 minutes 40 seconds long. Once you
are satisfied you sufficiently remember the content and features of these videos and descriptions, you can go on with
step 2. Note that you can always watch the videos again
when required.
Open the ‘CODING TEMPLATE’ file.
In this coding template Excel file, you will find several
sheet tabs consisting of different types of information:
The first sheet tab displayed when opening the file is the
Clarification & Instruction sheet, which explains the
symbols you’ll find on the other coding sheet tabs.
The other coding sheet tabs include ‘General’, ‘Actions’,
‘People’, ‘Vehicles’ and ‘Objects’. These sections represent
five categories to which the reported units of information are
to be assigned to. These five sheet tabs are the tabs you will
use to code the units of information stated within the
participant’s reports.
When browsing over these sheets, you will note that all
have the same structure:
On the left, you will find the list of units of information.
Units of information are sentences or parts that are
independent of all other information units, e.g. ‘the woman
with long blond hair’ are three independent units of information, namely, ‘woman’, ‘long hair’ and ‘blond hair’. As you
can see, the units of information displayed in this ‘General’
section mostly all display information that does not really
fit any of the other sections as they do not display specific
actions, people, vehicles or objects. The ‘General’ section
STEP 2
Single Vs. Repeated Traumatic Events 171
Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017)
therefore is a residual category in which you can assign units
of information too that are informative but do not fit in any of
the other four sections.
If a unit of information is aligned after an indentation, this
unit of information then is describing the first not indented
unit of information that is displayed above it. In the example
above, you see the unit of information displayed after the tab
space describes that ‘2—of the 3 female students—died’.
e.g. ‘the woman with long blond hair’ will be:
Open the ‘Participants reports’ file.
Here you will find the participants reports. These reports
consist of four sections. The first section (1) is a free recall
in which participants stated of the events that happened in
the target video. The second section (2 People) is about what
participants could remember of the people involved in the
video. The third section (3 Vehicles) is about vehicles, and
the fourth section (4 Objects) is about objects. As expected,
you will mostly find the same categorical units of information in the category section that they have been reported in.
However, it is possible that these sections contain units of
information of other sections as well.
You will find two reports per participant as they have
reported twice on the same video.
First reports are titled
‘Measure: S4 – SAI_1’
Second reports are titled
‘Measure: S5 – SAI_2’.
It is very important not to confuse these!
For one participant: copy the first report (Measure: S4 –
SAI_1) of the ‘Participants reports’ file into the ‘Report
1’ sheet tab of the ‘CODING TEMPLATE’ file. Copy the
second report (Measure: S5 – SAI_2) of the ‘Participants
reports’ file into the ‘Report 2’ sheet tab of the ‘CODING
TEMPLATE’ file. After this, write the participants’ number
in the ‘Total results’ sheet tab under SUBJECT NUMBER
(cell H2). Then save the Excel file in a map under the
following name: ‘Participant ..’ and write the participant’s
number on the ‘..’ space.
This way the new created file ‘Participant X’ is ready for
coding, and the Template File will remain empty for the next
participant. All coding preparations for this participant are
now performed.
When coding a report, analyse the report for independent
units of information and look whether the unit of information
occurs in one of the sections (general, actions, people,
vehicles, objects). If the unit of information is not occurring
in any of the lists, add it to the list by copying or writing
down the unit of information into the coding sheet under
the right section. It does not matter whether the reported unit
of information is correct or not! Automatically, a new row of
coding cells should appear:
Coding is performed by either or not changing the ‘0’ to a
‘1’ under the following sections:
C: When a unit of information is correctly reported; meaning that the reported unit of information occurs in the target
video or in its description (Appendix A). Replace the ‘0’ in
the row of the unit of information under the column C by a
‘1’. The background colour for this cell will automatically
turn green. When a unit of information is incorrectly
reported OR has a distortion leave the ‘0’ as a ‘0’.
D: When a unit of information is distorted; meaning that a
major detail has been changed and therefore is incorrect,
replace the ‘0’ in the row of the unit of information under
the column ‘D’ by a ‘1’. The background colour for this cell
will automatically turn red. When a unit of information is
correctly reported, leave the ‘0’ as a ‘0’.
Com: When a unit of information is reported but is not
occurring in the target video or its description, replace the
‘0’ in the row of the unit of information under the column
‘Com’ by a ‘1’. The background colour for this cell will
automatically turn red. When the reported unit of information is occurring in the target video or its description, leave
the ‘0’ as a ‘0’.
V1: When a reported unit of information is not occurring
in the target video or its description but is occurring in video
1, replace the ‘0’ in the row of the unit of information under
the column ‘V1’ by a ‘1’. The background colour for this cell
will automatically turn yellow. When the unit of information
is not occurring in video 1, leave the ‘0’ as a ‘0’.
Note: Only apply when the unit of information is
incorrect, distorted or a commission!
V2: When a reported unit of information is not occurring
in the target video or its description but is occurring in video
2, replace the ‘0’ in the row of the unit of information under
the column ‘V2’ by a ‘1’. The background colour for this cell
STEP 4
STEP 5
STEP 3
172 T. P. M. Theunissen et al.
Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017)
will automatically turn yellow. When the unit of information
is not occurring in video 2, leave the ‘0’ as a ‘0’
Note: Only apply when the unit of information is
incorrect, distorted or a commission!
>D<: When a reported unit of information in session 1 is
conflicting with another reported unit in session 2, replace
the empty space in the row of the unit of information under
the column ‘>D<’ by a ‘1’. The background colour for this
cell will automatically turn red. When the unit of information
is not conflicting throughout reporting sessions, leave the
empty space as it is.
Make sure you code the units of information of report 1
under the ‘Report session 1’ section and the units of
information of report 2 under the ‘Report session 2’
section.
When finished with coding both report 1 and report 2 for
one participant, save the ‘Participant X’ file.
Open the ‘OUTPUT EXCEL’ file. You will see an empty
OUTPUT DATA tab sheet with a row of categories in the
top row.
In the Participant X file under the tab section OUTPUT,
you will find a similar view with the same categories only
with 12 rows of data beneath it. These are the results
automatically calculated during coding. Check if these result
data comply with your coding work. Under category
SUBJECT, the participant number should appear you have
filled in under the SUBJECT NUMBER (cell H2) in the
Total Results tab sheet.
Copy these 12 rows of data from the Participant X file
into the OUTPUT file under the corresponding categories.
After this, save the OUTPUT file. For each next participant,
simply copy the 12 rows of output under the output of the
previous participant in the OUTPUT file.
Repeat these steps for each participant. When finished,
please send all the Participants X files and the OUTPUT file
back to me: [email protected]. Feel free
to contact this email address with any questions or comments
regarding this coding task.
Additional instructions
1. Make sure you do not state and code a unit of information
twice! For instance, in different categorical sections.
2. Try to avoid cutting or copying whole lists of rows; this
can disorder underlying cell formulas.
3. During coding, it might be handy to highlight the
reported units of information you have coded. This way,
you will always know where you have left off.
4. It can be handy to analyse a report for units of information by category and go to the next category when coding
for the current category is finished.
5. When coding the second report, it is very important that
you code the same unit of information in the same row
with that of the first report. Otherwise, these units will
account as two different independents units, which leads
to more (invalid) inconsistency.
6. Keep the Target Video open in a background window
as then it will be easy to quickly check for reference
when having doubts about the coding of a unit of
information.
7. It can be productive to check for Video 1 and Video 2
intrusions after you have coded all units of information
for correctness, distortions and discrepancies, and even
when you have this performed for all participants.
8. In every category tab sheet, there is a result section on the
right. It can be helpful to check frequently whether your
coding is correctly being summed up. If not, please
contact me [email protected] as there
might be an error in the coding template sheet. (O1, and
O2 (Omission) are units that are not reported but
occurring in the target video)
9. Coding can be a lengthy and exhausting process.
Make sure you take enough pauses in between to
avoid any fatigue errors.
Coding Manual Appendix A
These descriptions were presented to participants before
watching the corresponding video:
Video 1
These three men were involved in a multiple pile up on the
motorway. Unfortunately, two men died before they could
be taken to a hospital. One man did survive the accident
but sustained permanent dysfunction to one of his legs.
One of their wives, who was sitting in the passenger’s seat,
did survive the accident, although she sustained major
injuries.
Video 2
After a sudden rainstorm, several collisions occurred at one
spot on the motorway owing to the slippery conditions and
bad visibility. Eight people died, and of these, four died before they could be taken to a hospital. Here is a 21-year-old
woman who was trapped in her car. Unfortunately, she died
before she could be taken to hospital. The baby survived
the accident. The parents, 26 and 30 years old, also died
during the accident. One woman, a 20-year-old student,
sustained massive internal injuries, injured skull and deep
cuts to her face
STEP 6
Single Vs. Repeated Traumatic Events 173
Copyright © 2017 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 31: 164–174 (2017)
Target Video
These eight people were involved in a multiple car crash,
which resulted when one of the drivers lost concentration
and caused a head-on collision on the opposite lane. Among
the victims were three female students, two of whom died
and one who was severely injured. Two drivers of other cars
died before they could be taken to hospital, while two young
children sitting in the backseat were unharmed but in shock.