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APPLIED COGNITIVE PSYCHOLOGY
Appl. Cognit. Psychol. 15: S101±S117 (2001)
DOI: 10.1002/acp.766
Is Traumatic Memory Special? A Comparison
of Traumatic Memory Characteristics with Memory
for Other Emotional Life Experiences
STEPHEN PORTER
1
* and ANGELA R. BIRT
2
1
Dalhousie University, Canada
2
University of British Columbia, Canada
SUMMARY
According to the traumatic memory argument, traumatic experiences are processed and remembered
in a fundamentally different way from other life events. To investigate the validity of this theory, 306
participants were asked to give detailed accounts of two life experiences: their most traumatic
experience and their most positive emotional experience (counterbalanced). Participants also
described the qualities of each memory and completed psychological scales measuring severity of
trauma, personality, and dissociation. Results indicated that traumatic memories differed from non-
traumatic memories phenomenologically (e.g. vantage point) and qualitatively (e.g. number of
details). However, the memories also showed important similarities (e.g. high degree of vividness).
Only a small proportion (4.9%) of participants reported `recovering' their traumatic memories after
extended memory loss (most of whom reported consciously putting the experience out of aware-
ness), and 2.6% reported forgetting their positive experiences for an extended period. Overall,
traumatic memories were found to be `special', but not in accordance with prominent fragmentation
theories of trauma and memory. Copyright #2001 John Wiley & Sons, Ltd.
There has been a long-standing debate over how people remember traumatic experiences
(e.g. Loftus, 1993; Read and Lindsay, 1997; Toth and Cicchetti, 1998). According to one
widespread perspective known as the traumatic memory argument, stressful and traumatic
experiences lead to memory impairment because they are processed by cognitive
mechanisms that render them dif®cult to retrieve as coherent verbal narratives (e.g.
Herman, 1992). In contrast, a second perspective argues that traumatic stress does not
impair and can even enhance the quality of memory (e.g. Shobe and Kihlstrom, 1997), a
view which can be referred to as the trauma equivalency argument or trauma superiority
argument. The major question addressed in the current paper is whether traumatic
experiences are recalled in a fundamentally different manner than other life experiences.
The traumatic memory argument has its roots in the early psychodynamic tradition (e.g.
Porter and Marxsen, 1998). The nineteenth-century philosopher Arthur Schopenhauer
(1818/1896), and later Freud and his adherents, argued that aspects of stressful experiences
are commonly `repressed' and remain inaccessible in the recesses of the unconscious for
lengthy periods of time. According to Freud (1922), a traumatic event `subjects the mind to
such a very high increase of stimulation that assimilation or elaboration of it can no longer
Copyright #2001 John Wiley & Sons, Ltd.
Correspondence to: Stephen Porter, Department of Psychology, Dalhousie University, Halifax, Nova Scotia,
Canada, B3H 4J1. E-mail: sbporter@is.dal.ca
be effected by normal means, so that lasting disturbances must result' (p. 232). Janet (1925)
contended that highly stressful experiences narrow the ®eld of consciousness and result in a
dissociation of aspects of the traumatic memory from conscious awareness. He argued that
such events are remembered mainly in non-verbal, sensory form and as informational
fragments. Similarly, modern proponents of this view assert that traumatic experiences are
processed in a manner that renders memory for the trauma dif®cult to retrieve explicitly as a
coherent narrative. Van der Kolk (1996, 1997), for example, has proposed that elements of
traumatic experiences are remembered implicitly as sensory-motor and emotional frag-
ments, and that only these memory `fragments' are available in narrative form. Consistent
with this view, Herman (1992) asserted that aspects of traumatic memories lack a coherent
verbal narrative and context, existing mainly as changing non-verbal images and powerful
sensations. Recently, Brewin and colleagues (e.g. Brewin and Andrews, 1998; Brewin et al.,
1996) concluded that cognitive mechanisms could inhibit the activation of representations
of traumatic events. In their discussion of a dual processing model of post-traumatic stress,
Brewin et al. (1996) elaborated these inhibitory mechanisms, proposing that traumatic
memories can sometimes be represented non-verbally resulting from a non-conscious
processing of the traumatic situation. Writing as part of the American Psychological
Association working group on memories of childhood abuse, Alpert et al. (1996) wrote that
`trauma is by de®nition, so overwhelming, that it is dif®cult to face and to integrate
psychologically. Because of this, defensive strategies for management of this overwhelm-
ing material are needed and include dissociation and numbing that, in turn, can interfere
with memory processes' (p. 52).
Antithetical to the traumatic memory argument, the trauma equivalency/superiority
argument also has been long recognized. For example, Augustine observed that highly
emotional events `clung to [his] mind', so that they were easily remembered (see Herrmann
and Chaf®n, 1988). Similarly, William James (1890) remarked that an event could be so
emotionally stressful that it would almost `leave a scar upon the cerebral tissues' (p. 670).
More recently, a growing body of research indicates that high levels of real-life stress may
facilitate rather than impair the quality of memory. For example, studies of children who
had been kidnapped (Terr, 1983), witnesses to a homicide (Yuille and Cutshall, 1986),
survivors of a ferry sinking (Thompson et al., 1997), and concentration camp survivors
(Wagenaar and Groeneweg, 1990) suggest that memories for trauma can remain unim-
paired as vivid, coherent recollections. There is also a growing recognition that factors
other than the severity of the event itself may have the greatest impact on memory quality
(e.g. how often the event is thought about). Accordingly, many research psychologists
remain highly skeptical of the traumatic memory argument in the absence of more solid
scienti®c evidence (e.g. Loftus et al., 1998).
In addition to representing an important aspect of human cognition, the nature of
memory for trauma has relevance in both clinical and legal settings (e.g. Loftus, 1997;
Porter et al., 1999, in press). Research indicates that a substantial proportion of practising
clinicians in the 1990s were utilizing techniques to recover traumatic memories (e.g. Poole
et al., 1995). An issue at the heart of the recovered memory debate is whether such
techniques serve to reconstruct lost memories or, instead, lead to the creation of mistaken
memories (e.g. Lindsay and Read, 1994; Porter et al., 2000; Read, 1999). This is
particularly controversial in light of research demonstrating that people can be led to
recall events which never occurred (e.g. Hyman et al., 1995; Loftus and Pickrell, 1995; cf.
Pezdek et al., 1997), including events that would have been stressful had they actually
taken place (e.g. Porter et al., 1999). As Shobe and Kihlstrom (1997) pointed out,
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approaches seen as necessary to `weave' traumatic memories into the fabric of the
person's conscious awareness remain unsubstantiated.
According to some of the main arguments associated with the traumatic memory
perspective (outlined above), traumatic memories should have very different qualitative
and phenomenological characteristics compared to memories for other emotional life
events, at least prior to the postulated integrating effects of psychotherapy. For example,
compared with other highly emotional memories for life events, traumatic memories
should contain richer sensory components, higher levels of emotion, a lower level of
(visual) vividness/clarity, fewer narrative details, and poorer overall quality. In addition,
traumatic memories should be contemplated and discussed less often following the
incident (since elements of traumatic memories would not always available in verbal/
narrative form) than other non-traumatic emotional memories. Finally, it would be
expected that traumatic experiences may be more likely to be associated with reports of
extended periods of forgetting.
Little empirical research has examined the validity of these hypotheses. One recent
study found that women's memories of rape, and to a lesser extent negative experiences in
general, were less vivid, less meaningfully ordered, less well remembered, and contem-
plated less often than pleasant memories (Koss et al., 1996). However, only the self-
reported characteristics of the memories were investigated; no objective characteristics,
such as degree of detail in the memory accounts, were reported. Further, participants were
not questioned about whether the traumatic memories were ever forgotten and later
reconstructed in explicit narrative memory form. It also is not clear whether this pattern of
®ndings would be restricted to sexual violence or would extend to traumatic experiences in
general. Van der Kolk and Fisler (1995) studied 46 individuals who reported being haunted
by memories of a terrible experience. All the participants reported previous amnesia for
the experience, with the narrative memory emerging only later. However, along with other
methodological problems in the study, many of the reported memories were from early
childhood and the poor narrative qualities may have resulted from ordinary infantile/early
childhood amnesia.
In light of the controversies surrounding the nature of traumatic memory, the present
study was designed to investigate whether traumatic memories have unique qualities
relative to memories for other emotional life experiences. The proportion of people who
report having `forgotten' and later `recovered' traumatic memories compared to other
types of emotional memories also was investigated. Further, the relation between
individual differences (e.g. gender, personality, dissociation) and memory for traumatic
events was examined. Finally, participants were surveyed about their personal experiences
with recovered and false memories.
METHOD
Participants
Three hundred and six (N306) young adults from undergraduate university classes
participated in this study. They were recruited for research examining the nature of
traumatic memory and were given course credit points in exchange for their participation.
From a pool of potential subjects (312) who were informed about the study beforehand,
98.1% agreed to take part. The mean age was 21.8 years (SD 3.8) and females
constituted 76.5% of the sample.
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Materials and procedure
Prior to taking part, participants were required to read a detailed consent form outlining
the study and the sensitive nature of the topic being addressed. Following the informed
consent procedure, the participants completed a questionnaire called the `Emotional
Experiences Questionnaire' (EEQ) speci®cally designed for the present study. This
questionnaire took approximately 30 to 45 minutes to complete. In order to counterbalance
the order of the traumatic and positive memory descriptions, half of the participants were
asked to describe their most traumatic experience ®rst followed by their most positive
emotional experience, whereas the other half of participants received the opposite order.
The speci®c instructions for the traumatic experience were as follows:
Please take a few moments and think back to the most traumatic event you have ever
experienced. Choose a speci®c event as opposed to a series of events or a drawn-out
traumatic period. Next, take your time and report everything that you can remember.
Make sure to leave nothing out. Start at the beginning and give a complete
description of the entire event. Please be sure to include your age at the time of
the incident.
When participants ®nished their report, they were asked several questions relating to the
quality of their memory. The questions concerned vantage point or perspective (i.e. can
you see yourself in the memory?), anxiety/stress level, frequency of event discussion,
frequency of thinking about the event, vividness/clarity, sensory components (the presence
of each sense), and the overall memory quality (see the Appendix). Most of the criteria for
assessing memory quality were derived from the Memory Assessment Procedure (MAP),
operationalized in earlier research (Porter et al., 1999). To address whether the traumatic
experiences had ever been forgotten or had been inaccessible in memory, the following
questions were asked: (1) To your knowledge, was there ever an extended period when you
could not recall this event?(2) If so, what would you estimate was the longest period
during which you did not remember this event?(3) If so, did you choose not to recall it or
were you unable to recall it?(4) If so, which of the following reasons best explains it?
(unconsciously repressed it, intentionally put it out of the mind, simply forgot it, not sure,
other), (5) If so, please explain how you recovered the memory after that period (later
coded as in therapy, discussion with another person, popped into my head, don't know,
other).
The participants were instructed to describe their most positive emotional experience
with the same instructions as those used for the traumatic experience. They were also
asked similar questions (as applicable) concerning the characteristics of the memories. All
participants were instructed that the two experiences they chose to write about could be
from either childhood or adulthood, but that the occurrence of both events should
correspond to the same general life period.
After completing the EEQ, three psychological scales were administered to the
participants: the Revised Impact of Event Scale (IES; Horowitz., et al., 1979, 1980),
the Dissociative Experiences Scale (DES; Bernstein and Putnam, 1986; Carlson and
Putnam, 1993), and the NEO-Five Factor Inventory (NEO-FFI; Costa and McCrae, 1992).
The IES was intended to provide an index of the subjective level of traumatic stress and
perceived impact of the traumatic event reported. The DES was used to investigate the
relationship between trauma and dissociation. The NEO-FFI was administered to examine
the relation between personality and the qualities of traumatic memories.
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Revised Impact of Event Scale
The IES is a 15-item self-report scale that was designed speci®cally to assess the impact of
traumatic events. It measures level of subjective traumatic stress associated with a
particular event. Respondents are asked to rate each item according to the frequency of
its occurrence in relation to a speci®c experience of trauma on a scale marked 0 (not at all),
1 (rarely), 3 (sometimes), and 5 (often). Seven items evaluate event-related intrusion
memories/ideas and eight items measure avoidance of the memories, ideas, or associated
stimuli, yielding two subscale scores and a total score (where higher scores re¯ect greater
trauma impact). Horowitz et al. (1979) reported good psychometric properties for this
scale. It has been found to be reliable, to have concurrent validity with other trauma
inventories (e.g. Briere and Elliott, 1998), and to be sensitive to treatment effects among
sexual assault victims (e.g. Rothbaum, 1997). It is one of the most widely used instruments
to measure trauma symptoms and has been used with most trauma populations (e.g. Foa
and Rothbaum, 1998).
Briere and Elliott (1998) recently collected normative data on the IES in a large random
sample of individuals from the general population. Participants were categorized accord-
ing to the presence or absence of a history of serious trauma (i.e. childhood sexual abuse,
adult sexual assault, childhood physical abuse, adult physical assault, childhood/adulthood
witness to interpersonal violence, childhood/adulthood exposure to major non-interper-
sonal stressors (e.g. fatal vehicular accidents)). In this sample, the mean total IES score for
individuals with a history of trauma (n360) was 16.7, and 7.0 and 8.5 for the Intrusion
and Avoidance sub-scales, respectively. The IES has been scored in a number of ways. For
comparison purposes, we followed Briere and Elliott (1998) and calculated IES scores by
taking the sum of the frequency ratings for each individual.
Dissociative Experiences Scale
The DES is a self-administered 28-item questionnaire that measures tendency toward
dissociation (i.e. lack of the normal integration of thoughts, feelings, and experiences into
the stream of consciousness and memory). Some items relate to common dissociative
experiences (e.g. driving a car and recalling little of the trip) whereas others relate to more
severe dissociative experiences (e.g. seeing the world through a fog). The DES yields a
single score where higher scores are related to higher degrees of dissociative tendencies. A
score of 30 or greater is considered an optimal cutoff score for identifying the possibility
of a dissociative disorder (e.g. Bernstein and Putnam, 1986; Carlson et al., 1993; Foa and
Rothbaum, 1998). Its reliability, internal consistency, and construct validity have been
demonstrated (e.g. Carlson and Putnam, 1993).
NEO Five-Factor Inventory
The NEO-FFI is a 60-item questionnaire with ®ve 12-item scales providing a compre-
hensive measure of each of the ®ve major personality domains according to the Big-Five
Model: Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Con-
scientiousness. Neuroticism refers to the tendency to experience negative emotional states
and to view oneself and the world negatively. Extraversion refers to the propensity to
experience positive emotional states and to have a positive outlook on life (introversion is
conceptualized as the absence of extraversion). Extraverts are talkative, warm, gregarious,
and assertive. Openness to experience refers to the extent to which a person is original, has
broad interests, and is willing to take risks. Agreeableness refers to the tendency to get
along well with others and is associated with traits of trust, modesty, altruism, and
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compliance. Finally, conscientiousness refers to the extent to which a person is careful,
scrupulous, reliable, and persevering. The NEO-FFI is self-administered and each item is
answered on a 5-point scale, with anchors of 1 (strongly disagree) to 5 (strongly agree).
Its reliability, validity, and internal consistency values are high (see Costa and McCrae,
1992).
RESULTS
Preliminary analyses
Age when the emotional experiences occurred
Prior to conducting the major analyses, two potential confounding factors were examined.
First, the possibility of a difference between the ages when the traumatic and highly
positive experiences occurred was investigated. The mean ages for the traumatic
(M15.36, SD 5.38) and positive (M15.78, SD 5.26) events, were highly similar,
t(268) 1.21, p>0.05. Second, the possibility that memory for the emotional experi-
ences might be negatively in¯uenced by infantile/early childhood amnesia was explored.
However, only six of the 306 participants reported traumatic experiences that occurred
under age ®ve (minimum age three) and only ®ve reported positive experiences that
occurred under age ®ve (minimum age three). This suggested that childhood amnesia was
not a signi®cant confound.
Reliability of coded variables
Some of the memory criteria examined in this study were in the form of subjective ratings
provided by the participants. However, three measures concerned the objective content of
the memory reports (number of details, coherence,andreferences to emotional state; see
the Appendix). These were coded by trained coders na
ve to the nature and predictions of
the experiment. Inter-coder reliabilities were computed for these criteria using 51 (16.7%)
randomly selected reports. The most appropriate approach to calculating inter-coder
reliability for this type of data (see Orwin, 1994) was to examine correlations between the
decisions of coders followed by a mean difference test. The coders attained acceptable
reliability on all criteria: number of details, r(50) 0.89, p<0.0001, t(49) 0.26,
p>0.05; coherence, r(50) 0.76, p<0.0001, t(49) 1.8, p>0.05; and emotional com-
ponents, r(50) 0.88, p<0.0001, t(49) 0.48, p>0.05.
Emotional experiences reported
As expected, there were several different types of experiences reported by participants for
both the highly positive and traumatic memories. For the positive experiences, the most
common events reported were: winning a major award/competition or achieving fame
(34.6%), major relationship event (19.6%), graduation (19.0%), exciting incident on a trip/
vacation (11.4%), witnessing a birth (2.9%), and other (14.5%). The most common
traumatic experiences were: the death of a loved one, a serious accident, physical violence,
family disintegration, serious medical condition/near-death experience, and sexual vio-
lence/abuse (see Table 1).
1
1
Sample memory narratives are available to interested readers. Please contact the ®rst author to obtain these
materials.
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Level of trauma reported
The mean stress rating (1 not at all stressful to 7 extremely traumatic) of the 306
traumatic events reported was 6.30 (SD 1.08). Overall, 84% of participants provided a
stress rating of either `6' (26.8%) or the maximum of `7' (57.2%). The mean total IES
score was 17.41 (SD 18.18). The mean Intrusion sub-scale score was 9.12 (SD 9.9)
and the mean Avoidance sub-scale score was 8.29 (SD 9.5). These scores were slightly
higher than the those reported by Briere and Elliott (1998). The majority of participants
reported that their dominant emotion at the time of the traumatic experience was either
intense fear (38.6%) or sadness (27.1%). Together, these data suggested that the `most
traumatic events' reported had indeed been highly traumatic to the participants.
Comparison of traumatic and positive memories
To examine whether there were differences between memories for the traumatic and
positive emotional experiences, a within-subjects multivariate analysis of variance
(MANOVA) was conducted with the phenomenological and objective qualities of the
memories as dependent variables. This analysis yielded a signi®cant result, Hotellings
T
2
1.96, F(9, 136) 20.95, p<0.0001. As Table 2 demonstrates, the data indicated that
compared to highly positive memories, traumatic memories had fewer sensory compo-
nents, F(1, 144) 15.93, p<0.0001, were more likely to have a `participant' perspective,
F(1, 144) 5.52, p<0.05, and had been thought about more often, F(1, 144) 7.71,
p<0.01. Additionally, the traumatic memory accounts contained signi®cantly more
details, F(1, 144) 105.32, p<0.0001, and more references to emotional state at the
time of the event, F(1, 144) 11.45, p<0.001.
Although traumatic memories had signi®cantly fewer sensory components than positive
memories, it was not clear which of the sensory modalities differed. Follow-up analyses
indicated that traumatic memories had fewer taste components than positive memories,
with 4.9% of participants reporting being able to remember the taste of something in their
traumatic memory compared to 13.4% in their positive memory, t(292) 3.46, p<0.001.
Apart from this difference, the two memory types were similar with regard to sensory
components.
Table 1. Categories of the most traumatic experiences reported
Event category % Mean stress rating (1±7) (SD)
Death of a loved one 26.5 6.3(1.0)
Serious accident 22.5 6.2(1.0)
Physical violence 10.8 6.3(1.3)
Relationship breakup/divorce 10.5 6.6(0.7)
Serious medical condition/near-death 6.5 6.7(0.8)
experience
Sexual assault/abuse 5.2 5.4(2.0)
Embarrassment/negative evaluation 4.9 6.6(0.5)
Death of pet 4.9 6.5(0.7)
Family moved 2.0 6.0(1.3)
Arrested/trouble with law 2.0 6.3(0.5)
Got lost for extended period 2.0 6.8(0.4)
Witnessing other's trauma 2.0 6.7(0.6)
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Memory quality as a function of traumatic stress
The possibility that memories for events associated with more traumatic stress symptoms
had different features from events with fewer traumatic stress symptoms was considered.
Based on the IES scores, the traumatic experiences were trichotomized into equal groups
based on level of subjective post-event trauma symptoms (low, moderate, or severe). A
between-subjects MANOVA examined possible differences in the memory qualities as a
function of reported trauma symptom severity. In addition to the measures described
above, DES scores also were entered as a dependent measure to examine the relationship
between level of subjective impact of trauma and dissociation. The MANOVA yielded a
signi®cant result, Wilk's lambda 0.72, F(18, 282) 2.85, p<0.0001. Univariate ana-
lyses indicated that different levels of perceived impact of trauma were associated with
different: (a) frequencies of thinking about the event, (b) frequencies of discussing
the event, (c) number of emotional components, and (d) DES scores (see Table 3).
Table 2. Comparison of the qualities of traumatic and positive memories (means and standard
deviations)
Memory feature Traumatic memory Positive memory
Vividness/clarity of the memory (1±7) 5.76(1.29) 5.89(1.20)
Sensory components in the memory (1±5)*** 2.19(.89) 2.56(1.18)
Quality of the memory (1±7) 5.77(1.34) 5.78(1.23)
Perspective in the memory image (1±3)* 1.79(.84) 1.68(.82)
Frequency of event discussion (1±7) 3.76(1.88) 3.82(1.83)
Frequency of thinking about the event (1±7)** 5.13(1.76) 4.55(1.73)
Number of details*** 28.52(17.93) 19.66(14.59)
Number of emotional components*** 2.59(2.95) 2.08(1.95)
Coherence (1±3) 2.87(.34) 2.92(.67)
*p <0.05; **p <0.01; ***p <0.001.
Table 3. Memory quality as a function of severity of trauma according to IES scores (means and
standard deviations)
Memory feature Low trauma Moderate trauma Severe trauma
Vividness/clarity of the memory 5.64(1.16) 5.73(1.31) 5.91(1.38)
(1±7)
Sensory components (1±5) 2.05(.89) 2.19(.83) 2.35(.96)
Quality of the memory (1±7) 5.56(1.27) 5.86(1.29) 5.89(1.44)
Perspective in the memory 1.72(.81) 1.84(.85) 1.81(.86)
image (1±3)
Frequency of event discussion 3.40(1.77) 3.72(1.77) 4.14(2.04)
a
(1±7)*
Frequency of thinking about the 4.40(1.71) 5.11(1.73)
a
5.86(1.56)
ab
event (1±7)***
Number of details 28.32(16.77) 30.48(19.46) 26.77(17.40)
Number of emotional 2.91(3.67) 2.00(1.84) 2.86(3.01)
components*
Coherence 2.88(.33) 2.87(.34) 2.85(.35)
Dissociative experiences scale 9.32(7.75) 14.66(9.45)
a
18.24(13.35)
ab
(DES) score***
Note: A letter superscript (a, b) indicates that the given mean was signi®cantly (p<0.05) higher than the mean
of the other group(s) (in order: a, b, c). *p<0.05; **p<0.01; ***p<0.001.
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Tukey comparisons (p's <0.05) indicated that participants who reported higher levels of
traumatic stress (as measured by the IES) reported thinking about the event more often
than those who had rated their traumatic stress as lower. Moderate ratings of impact of
trauma also were associated with thinking about the event more often than low ratings.
Second, participants who reported high levels of traumatic stress reported discussing the
event more often than those who had experienced a low level of trauma. Third, all groups
differed from one another on DES scores, with a greater perceived impact of trauma
associated with higher DES scores. There was a modest positive correlation between IES
scores and memory vividness/clarity, r(305) 0.12, p<0.05, indicating that events
associated with more traumatic stress symptoms were recalled more vividly.
Were memories for sexual and non-sexual violence distinct?
Overall, 30 participants (9.8%) reported having been sexually assaulted at least once (eight
reported repeated abuse). Nine of these participants described a sexual assault as their
most traumatic experience. It has been suggested that sexual violence may be recalled
differently from other traumatic experiences due to elements of intrusiveness and
disillusionment. To examine this hypothesis, the traumatic events were dichotomized
into sexual violence/abuse and non-sexual physical violence. A MANOVAwas signi®cant,
Hotelling's T
2
0.88, F(8, 22) 2.43, p<0.05. Memories for sexual violence were
associated with higher levels of vividness/clarity (M6.38, SD 0.96) than memories
for other violent events (M5.30, SD 6.38), F(1, 47) 7.59, p<0.01. Sexual abuse
memories also had more sensory components (M2.58, SD 0.79) than other violent
memories (M1.90, SD 0.91), F(1, 30) 4.63, p<0.05. Further, there was a trend for
the sexual abuse memories to be rated as having a higher overall quality (p0.08) than
memories for other violence.
Individual differences and the experience of trauma
Gender
The possibility that males and females recalled traumatic experiences differently was
investigated. A between-subjects MANOVA (gender as the independent variable) focusing
on both subjective memory qualities and the perceived personal impact of the traumatic
event was conducted. The MANOVA was signi®cant, Hotelling's T
2
0.20, F(12,
139) 2.34, p<0.01. Overall, there were no qualitative differences between males' and
females' recollections of their trauma. However, females reported thinking about the
traumatic experience (M5.29, SD 1.71) signi®cantly more often than males
(M4.63, SD 1.83), (F[1, 304] 2.22, p<0.01), and provided more details in their
memory accounts (M29.97, SD 18.25) than males (M23.86, SD 16.10),
F(1, 302) 6.48, p<0.05.
Personality
The relationships between the ®ve major personality factors of the NEO-FFI with IES and
DES scores were examined through correlational analysis. Total scores on the IES were
modestly related to neuroticism, r(305) 0.17, p<0.01, as were the Intrusion sub-scale
(r(305) 0.14, p<0.05) and the Avoidance sub-scale (r(305) 0.13, p<0.05) scores.
DES scores were signi®cantly related to neuroticism (r(305) 0.21, p<0.001), agree-
ableness (r(305) 0.15, p<0.05), and conscientiousness (r(305) 0.14, p<0.05).
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Dissociation
DES scores also showed a positive association with overall IES scores, r(304) 0.30,
p<0.0001. In addition, there were signi®cant positive correlations between DES scores
and IES Intrusion sub-scale scores, r(304) 0.28, p<0.0001, and Avoidance sub-scale
scores, r(304) 0.19, p<0.01.
Did participants ever forget the traumatic experience?
Overall, 14 of the 306 (4.6%) participants reported that there had been an extended time
period during which they did not recall their traumatic experience. Eleven of the 14
(78.6%) participants indicated that they had consciously chosen not to recall the event.
Speci®cally, six reported intentionally putting it out of their minds, three simply forgot,
and two did not know. The other three participants reported that they had no conscious
control over the forgetting and that they had unconsciously repressed the traumatic event.
The mean reported forgetting period was 621.0 days (SD 1062.55) with a range of three
to 3650 days (ten years). The 14 participants who reported forgetting their traumatic
experience were asked to describe how they had come to recover the memory, if they
knew. Six (42.9%) reported that the memory had spontaneously `popped' into the mind,
®ve (35.7%) reported that they were unsure, while three (21.4%) reported that the memory
had been recovered during a discussion with another person. Two of the three participants
who reported having unconsciously repressed the memory described the recovery process
as spontaneous, with the memory popping into their minds. The other reported that it had
been recovered in a discussion with another person.
Eight participants (2.6%) in the sample reported that there had been an extended period
of forgetting for their most positive experience. This self-reported forgetting had a mean
duration of 244.1 days (SD 377.53) and ranged from two days to three years. One
participant reported an extended period of forgetting for both the traumatic and positive
experiences.
Survey about repression and memory distortion
Participants were asked their view on whether it is possible to `repress' a traumatic
experience. Overall, 85.3% of the sample responded yes, 4.9% responded no, and 9.8%
were uncertain. They also were questioned whether any friend or family member had ever
disclosed their own recovery of a traumatic memory following an extended period of
forgetting. Overall, 14.4% (n44) responded that someone had disclosed to them such a
report of a recovered memory.
Next, participants were asked whether they were aware with certainty that they had ever
experienced a memory for an entire event which they later discovered had de®nitely not
occurred. Overall, 59 respondents (19.3%) reported that they were certain they had
experienced at least one complete mistaken memory. In previous studies, people who were
susceptible to experimentally implanted false memories showed higher DES scores than
non-susceptible individuals (e.g. Hyman and Billings, 1998; Porter et al., 2000). In the
present study, participants who had experienced a false memory scored signi®cantly
higher on the DES (M17.19, SD 11.45) than their counterparts (M13.43,
SD 10.91), t(301) 2.35, p<0.05. They also had higher scores (M55.9, SD 10.6
versus M52.0, SD 10.6) on the openness to experience scale on the NEO-FFI,
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F(1, 287) 6.33, p<0.01, and there was a trend for them to score lower on the
conscientiousness scale.
DISCUSSION
Is traumatic memory special?This question has been the focus of a lengthy scienti®c
debate and has both basic and applied implications (e.g. Read, 1999). One view, the
traumatic memory argument, has received considerable attention in clinical contexts.
Proponents of this perspective maintain that traumatic experiences are recalled in
an impaired (fragmented, sensory/emotional) fashion rather than as coherent verbal
narratives. According to a second view, the trauma superiority/equivalency argument,
traumatic experiences are recalled similarly to, and perhaps even better than, other
experiences.
Overall, the results of the present study provided evidence for the latter theory.
Participants reported a range of highly traumatic life experiences, from witnessing a
death to sexual assault. These traumatic memories were associated with a richness of
detail and more emotional information compared to positive emotional memories.
Traumatic memories were recalled with fewer sensory components (as in Koss et al.,
1996) and were thought about more often than positive experiences. The fact that
traumatic memories were thought about more often would appear, prima facie, to cast
doubt on the idea that aspects of the trauma are inaccessible, contrary to fragmentation
theories. On the other hand, one could conceive of a person who after experiencing trauma
`thinks about' the experience frequently even though he or she cannot provide a narrative
account of some aspects of the experience. However, the positive and negative emotional
memories shared some important phenomenological characteristics that seem to provide
additional support for trauma equivalency/superiority arguments. In particular, they were
similar in their high degree of vividness, coherence, and overall quality which provides
evidence against any signi®cant impairment in the traumatic memories.
It might be argued that memory impairment only occurs for experiences associated with
very severe trauma. However, our results indicated that the reported level of post-event
trauma symptoms had no apparent negative impact on the quality of the memories. In fact,
traumatic events associated with the highest levels of perceived impact and traumatic
stress were thought about and discussed more frequently than other traumatic events
reported, which contradicts the traumatic memory argument. In addition, memories for
sexual assault (often cited in fragmentation theories) were recalled more vividly than other
memories for violence. Nonetheless, those traumatic experiences with high levels of
perceived impact of trauma were associated with higher levels of dissociation (in terms of
higher DES scores). This suggests that either proneness to dissociation results in
perceiving negative events as more traumatic and having a greater impact on one's life,
or that a highly traumatic experience can result in dissociative symptomatology. Although
it is dif®cult to establish the directionality of the relationship empirically, some forms of
dissociation are widely understood to be responses to trauma in the clinical literature (e.g.
Gershuny and Thayer, 1999; Putnam and Carlson, 1998).
One controversy surrounding memory for trauma is whether it is possible to `forget'
highly emotional or traumatic experiences. In the present study, rather than having been
unable to recall aspects of their trauma for extended periods of time, most participants
reported continuous memories of the traumatic event. In fact, participants reported
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thinking about their traumatic experiences more often than their positive experiences ± a
®nding that casts doubt on the idea that aspects of trauma are inaccessible in narrative
form. Only 4.6% of this sample reported that there had been an extended period during
which they were unable to recall their most traumatic experience. Most participants who
had ``forgotten'' the event reported that they had consciously forced it out of their minds
(suppressed the memory), rather than repressed it. Notably, 2.6% of participants reported
that they had forgotten their most positive experience for an extended period, demonstrat-
ing that highly emotional events of both negative and positive valence can be `forgotten'
and subsequently reconstructed in memory (see also Read and Lindsay, 2000).
The role of individual differences in traumatic memory has received little attention in
previous research. Here, we found that gender and personality were related (although
modestly) to the quality of traumatic remembering. Speci®cally, women thought about the
traumatic experience more often and reported more details in memory (it is unclear
whether this re¯ects a true phenomenological difference or a difference in reporting style).
As well, the perceived impact of the event was positively associated with neuroticism.
Further, higher dissociation scores were positively related to neuroticism and negatively
related to agreeableness and conscientiousness. Again, the directionality of these relation-
ships is dif®cult to ascertain. It is possible that personality characteristics in¯uence the
perception of the event. Equally plausible is the explanation that traumatic experiences
in¯uence personality characteristics in signi®cant ways. For example, it is certainly
conceivable that neuroticism and associated anxiety could result from or be augmented by
a traumatic experience.
Re¯ecting the continuing popularity of the concept, most participants felt that repres-
sion was a valid phenomenon. Perhaps more surprising was the signi®cant number of
participants (14.4%) who reported being told about a `recovered' repressed memory by a
friend or family member. Although the accuracy of these accounts is unknown, this
suggests that memory recovery is a common phenomenon. Given the relevance of the
issue to the recovered memory debate, participants were also asked whether they were
aware if they had experienced at least one complete mistaken memory for an entire event
that never occurred. A surprising number (19.3%) reported they were aware of such a false
memory. Previous experimental research has indicated that susceptibility to false mem-
ories is positively related to dissociation (e.g. Hyman and Billings, 1998; Porter et al.,
2000). Similarly, in this study, it was shown that even self-reported experiences of false
memories were associated with substantially higher levels of dissociation.
This study provides important information on the phenomenology of traumatic
memory. However, it is important to consider the generalizability of the ®ndings. The
participants were students whose traumatic experiences may not represent those of clinical
samples. Nevertheless, most of the events described were certainly frightening, upsetting,
and/or painful. Further, the stress ratings associated with the events were very high.
Finally, IES scores collected here were higher than those reported previously for a large
sample of individuals from the general population with a history of trauma (Briere and
Elliott, 1998). Therefore, it is likely that these were indeed highly traumatic events.
Nonetheless, in our future research we plan to extend this methodology to forensic and
clinical samples to help to clarify the generalizability issue. Another consideration is the
possibility that more severe traumatic events did not get reported (relating to a number of
potential mechanisms). Although this is obviously a dif®cult issue to resolve empirically,
it may not have been a major problem here. First, nearly all participants who were eligible
to participate chose to do so (98.1%), suggesting that a bias for only those with less severe
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traumatic experiences to participate is unlikely.
2
Second, most participants in this study
did report highly traumatic experiences (including sexual and physical violence) and
recalled them vividly. Finally, it is possible that some participants might have chosen not
to report their most traumatic experience even though they had not repressed it. However,
this seems unlikely given the high stress and perceived impact of trauma ratings that were
obtained.
Despite these possible limitations, our ®ndings have signi®cant implications for the
understanding of memory and trauma. The results indicated that traumatic memories are
unique in terms of how often they are thought about and discussed, their degree of sensory
material, amount of detail, amount of emotional information, and the vantage point from
which they are recalled. On the other hand, some memory characteristics were similar to
highly positive and other negative emotional memories, and the level of perceived impact
of the trauma was not a major factor in memory quality. Overall, the traumatic memories
were rich, coherent, intrusive, and detailed rather than impaired in any way. Therefore, we
conclude that traumatic memories are `special', but not in accordance with prominent
fragmentation theories.
ACKNOWLEDGEMENTS
The ®rst author is supported by grants from the Social Science and Humanities Research
Council of Canada (SSHRC) and the Dalhousie University Faculty of Science. The second
author is supported by a doctoral fellowship from the University of British Columbia. The
authors would like to extend thanks to Naomi Doucette, Alexandra Howard, Stephen
Lewis, Rob MacArthur, Jette Midtgaard, Alicia MacDonald, and Jennifer Stapleton for
their help with test scoring and coding the questionnaires. Thanks to Mary Ann Campbell,
the anonymous reviewers, and Don Read for helpful comments on an earlier draft of this
manuscript. Appreciation is also extended to all participants for sharing their emotional
experiences for this research.
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APPENDIX: DESCRIPTION OF THE MEMORY CRITERIA
Also see Porter et al. (1999) for further information on the Memory Assessment Procedure
(MAP)
Part 1 ± Phenomenological (Subjective) Characteristics
Item 1. Vividness/Clarity. This criterion refers to how vivid and clear the childhood
memory is for the person experiencing it. Each participant was asked to indicate how
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vivid and clear his/her memory was for each event on a scale of 1 to 7 (1 not at all
vivid and clear to 7 completely vivid and clear).
Item 2. Stress Ratings. Each participant was asked to rate the level of stress associated
with the event in question according to a 7-point scale (1 not at all stressful to
7extremely traumatic).
Item 3. Sensory Components. This criterion assesses the level of sensory information
that is re-experienced when an event is remembered (from the reality monitoring
model). Each participant was asked to indicate whether each memory contained a
visual, auditory, olfactory, tactile, and gustatory component. For coding purposes, each
memory was scored from 1 to 5, depending on the number of sensory components.
Item 4. Quality of the Memory. Each participant was asked to rate the overall quality of
the memory in question on a 7-point scale (1 very poor to 7 excellent).
Item 5. Vantage Point (Participant/Observer). This criterion measured whether a `par-
ticipant' or `observer' perspective dominated the memory image. A participant perspec-
tive refers to a memory in which the event is re-experienced through the person's own
eyes. An observer perspective refers to a memory in which the remember can see him/
herself acting in the memory image. Each participant was asked to report whether he or
she could see him/herself in the memory image and which of the two perspectives best
characterized the image. Participants were also given the option of reporting that the
memory perspective changed (1±3; 1 I can never see myself in the memory, 2 the
memory changes so that I can see myself in the memory image only some of the time,
and 3 I can always see myself in the memory). Thus, ratings increased from a parti-
cipant perspective to a more dominant observer perspective.
Item 6. Frequency of event discussion. Participants were asked to estimate how
frequently they had discussed the event with others on average per year since its occur-
rence on a 7-point scale, with 1 (never), 4 (approximately three times per year), and 7
(6 per year).
Item 7. Frequency of thinking about the event. Participants were asked to estimate
how frequently they had privately thought about the event on average per year since
its occurrence according to a 7-point scale, with 1 (never), 4 (a few times per year),
and 7 (7 per year).
Part 2 ± Objective Characteristics
Items 8 (Detail) and 10 (Coherence) derive from the Statement Validity Analysis (SVA)
technique developed in Germany in the 1950s and later operationalized and formalized by
an international group of researchers (see Horowitz, 1991; Landry and Brigham, 1992;
Porter and Yuille, 1996; Porter et al., 1995; Raskin, 1989; Raskin and Esplin, 1991;
Zaparniuk et al., 1995). They were later adopted and re®ned for the Memory Assessment
Procedure (MAP: Porter, 1998; Porter et al., 1999).
Item 8. Amount of Detail. This criterion refers to how much detail is contained within a
memory report. This was coded via an existing scoring procedure (above) in which each
distinctive piece of information offered is scored one point. For example, `John ran into
the woods behind his house' contains three speci®c details (the identi®ed person, action,
location). `Dad was carrying a red coat and a scarf' contains four details ± one action
(carrying) and three descriptives (Dad, red coat, scarf). Very general, non-speci®c infor-
mation such as `a man' in `A man walked out' warranted 1/2 point.
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Item 9. Number of Emotional Components. The coders scored each memory report
transcript for the number of references made to the participants own emotional state
(e.g. `I was terri®ed', `I felt so angry', `I could tell she was sad').
Item 10. Coherence. This was coded via an existing scoring procedure (e.g. Porter et al.,
1995, 1999; Porter and Yuille, 1996). Each account was rated on how well it hung
together and followed a logical sequence and re¯ected consistency over time. That is,
it re¯ects consistency over time (the story has a beginning, middle, and an end provided
in chronological order). As well, how consistent is the information provided?Does the
person contradict him/herself?The coder must make a rating of how coherent and
logical the memory is overall (e.g. a minor inconsistency would not render the account
incoherent).
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