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Running head: BELIEFS ABOUT STRESS AND MEMORY
The Effects of Stress on Eyewitness Memory:
A Survey of Memory Experts and Laypeople
Carey Marr1,2*, Henry Otgaar1,3, Melanie Sauerland1, Conny Quaedflieg1, & Lorraine Hope2
1Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands
2Department of Psychology, University of Portsmouth, Portsmouth, UK
3Faculty of Law, Catholic University of Leuven, Leuven, Belgium
In Press, Memory & Cognition
Author Note
We have no known conflict of interest to disclose.
This research was supported by a fellowship awarded from the Erasmus Mundus Joint
Doctorate Program The House of Legal Psychology (EMJD-LP).
Correspondence concerning this article should be addressed to Carey Marr,
Universiteitssingel 40, Maastricht, Netherlands 6229 ER, Contact:
carey.marr@maastrichtuniversity.nl, +31642734493
BELIEFS ABOUT STRESS AND MEMORY
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Abstract
This survey examined lay and expert beliefs about statements concerning stress effects on
(eyewitness) memory. Thirty-seven eyewitness memory experts, 36 fundamental memory
experts, and 109 laypeople endorsed, opposed, or selected don’t know responses for a range of
statements relating to the effects of stress at encoding and retrieval. We examined proportions in
each group and differences between groups (eyewitness memory experts vs. fundamental
memory experts; experts vs. laypeople) for endorsements (agree vs. disagree) and selections
(don’t know vs. agree/disagree). High proportions of experts from both research fields agreed
that very high levels of stress impair the accuracy of eyewitness testimony. A majority of
fundamental experts, but not eyewitness experts, endorsed the idea that stress experienced during
encoding can enhance memory. Responses to statements regarding moderating factors such as
stressor severity and detail type provided further insight into this discrepancy. Eyewitness
memory experts more frequently selected the don’t know option for neuroscientific statements
regarding stress effects on memory than fundamental memory experts, although don’t know
selections were substantial among both expert groups. Laypeople’s responses to eight of the
statements differed statistically from expert answers on topics such as memory in children, in
professionals such as police officers, for faces and short crimes, and the existence of repression,
providing insight into possible ‘commonsense’ beliefs on stress effects on memory. Our findings
capture the current state of knowledge about stress effects on memory as reflected by sample of
experts and laypeople, and highlight areas where further research and consensus would be
valuable.
Key words: stress, memory, expert, laypeople, commonsense belief
BELIEFS ABOUT STRESS AND MEMORY
3
Witnesses often experience acute stress in forensic contexts, whether during a crime or
during subsequent police interviews (Bornstein et al., 2013; Davis, 2016; Yuille & Cutshall,
1986). Facing difficult, frightening, and emotional events can trigger a subjective and
physiological stress response from the witness (Bornstein & Robicheuax, 2009). A body of
research has been devoted to examining the potential effects of acute stress on memory, but
results have been inconsistent. Equally important, there is little information about current
memory experts’ and laypeople’s knowledge about the stress-memory relationship. Memory
experts in different research domains, such as eyewitness memory experts and fundamental
memory experts, as well as laypeople, may have different understandings of this relationship. If
different perspectives exist, such differences could emerge in courtroom settings in problematic
ways. For example, memory researchers from different fields might be asked to be expert
witnesses in court, and then provide diverging statements concerning stress-memory
relationships. Additionally, laypeople acting as jurors may evaluate eyewitness evidence based
on their pre-existing ‘commonsense’ beliefs. To capture the contemporary perspectives of
memory experts and laypeople, we examined current memory experts’ and laypeople’s beliefs
about the effects of acute stress on memory by means of a targeted survey.
Stress and Memory: An Ongoing Discussion
Two groups of memory researchers have examined the effects of acute stress on memory
encoding and retrieval. One group predominantly concentrates on memory in applied settings,
such as eyewitness memory, and the other group mainly focuses on fundamental memory
research, including neurobiological research related to basic memory processes (e.g., memory
performance for non-complex stimuli, such as word lists or numeric strings). Generally, across
fields, research shows that acute stress at retrieval impairs memory (e.g., Schwabe et al., 2012;
Shields et al., 2017; Wolf, 2017), although limited research on this specific issue has been
BELIEFS ABOUT STRESS AND MEMORY
4
conducted in the eyewitness memory context (see Dellapaolera, 2019; Robicheaux, 2016).
However, findings concerning the effects of acute stress at encoding on memory performance
appear to be discrepant between research fields (Christianson, 1992; Schwabe et al., 2012;
Shields et al., 2017). Eyewitness memory research mostly concludes that encoding stress impairs
eyewitness memory. For example, a meta-analysis of 27 eyewitness memory studies suggested
that heightened stress exerts a negative effect on eyewitness memory for both the perpetrator and
details associated with the crime (Deffenbacher et al., 2004). Eyewitness memory researchers
often cite such research as evidence that the negative effect of encoding stress on memory is a
conclusive finding (e.g., Schmechel et al., 2006; Yarmey & Jones, 1983). For example,
Schmechel and colleagues (2006) stated that “highly stressful situations may make an experience
seem especially vivid, but such stressors can reduce the ability to recall details about a person’s
face”, declaring this summary of stress effects as an “empirical answer” (p. 179). Field studies in
this area have also highlighted a negative effect of severe encoding stress on memory (e.g.,
Metcalfe et al., 2019; Stanny & Johnson, 2000; Valentine & Mesout, 2008). For instance, in one
study, active-duty military personnel participated in a survival school training exercise (Morgan
et al., 2004). During training, participants experienced one low-stress interrogation and one high-
stress interrogation and were later asked either to make identification decisions for each of the
two interrogations from a live lineup (Study 1) or a photo lineup (Study 2). In two subsequent
studies, all participants were either in the high stress (Study 3) or low stress condition (Study 4)
and made an identification decision from a sequential photo lineup. Regardless of assessment
method, identification performance was better for low-stress interrogators compared to high-
stress interrogators. However, it should be noted that several other factors in this field study are
potentially confounding variables, such as the fact that all soldiers participating in the research
were deprived of food and sleep for 48 hours prior to the interrogations. These naturalistic
BELIEFS ABOUT STRESS AND MEMORY
5
elements of the survival training context likely impacted the stress-memory relationship beyond
the effects of acute stress alone.
The view that stress at encoding negatively affects subsequent memory is in contrast to
findings reported in fundamental memory research, which demonstrate that acute stress at
encoding can actually enhance memory performance (e.g., Henckens et al., 2009; Shields et al.,
2017; Vogel & Schwabe, 2016; Wolf, 2012). These findings can be accounted for in terms of the
cognitive effects of physiological stress responses triggered by acute stress. When we experience
acute stress, adrenaline and noradrenaline are quickly released, followed by the slower release of
cortisol from the activation of the hypothalamic-pituitary-adrenal (HPA) axis (e.g., Joëls &
Baram, 2009, Joëls et al., 2011; Robbins, 1984; Ulrich-Lai & Herman, 2009). The rapid
catecholaminergic and non-genomic glucocorticoid actions set the brain in a memory formation
mode (Diamond et al., 2007; Joëls et al., 2006). If encoding occurs during this part of the
memory phase, acute stress should enhance memory formation for stress-related material, while
also impairing retrieval of material unrelated to the stressor (e.g., Diamond et al., 2007; Joëls et
al., 2006; Quaedflieg & Schwabe, 2018; Shields et al., 2017). Methodological differences
between eyewitness research and fundamental memory research may explain these contradictory
results. For example, differences in the type and severity of stressors, the timing between a
stressor and encoding, and retention intervals between encoding and retrieval could result in
varied findings (for discussions of potential participant and study design moderators, see
Sauerland et al., 2016; Shields et al., 2017; Shields, 2020; Thomas & Karanian, 2019).
These diverging research findings with respect to how stress at encoding impacts memory
performance suggest that disagreement might also exist between different types of experts about
topics related to acute stress and memory. Additionally, beliefs held by the general population
about stress and memory do not always mirror expert knowledge (e.g., Yarmey & Jones, 1983).
BELIEFS ABOUT STRESS AND MEMORY
6
Past surveys have examined some general beliefs about stress and memory among both lay and
expert samples. Table 1 presents an overview of 17 published surveys that we located on this
topic, published from 1979, with the most recent published in 2010. Across all 17 surveys, 79%
of laypeople agreed that high stress harms the accuracy of eyewitness testimony (survey
responses ranging from 41% to 92%). Three surveys examining experts’ beliefs about the
negative effects of stress on eyewitness memory between 1983 and 2001 show a slight decline in
agreement (Kassin et al., 1989, 2001; Yarmey & Jones, 1983). In 1983, 88% of experts (N = 16)
agreed with the statement that When a person experienced extreme stress as the victim of a
crime, he/she will have reduced ability to notice and remember the details of the event (Yarmey
& Jones, 1983). In 1989, 73% of eyewitness experts (N = 63) agreed that the statement Very high
levels of stress impair the accuracy of eyewitness testimony was reliable enough to present in
court (Kassin et al., 1989). By 2001, agreement levels had dropped to 60% (N = 62; Kassin et al.,
2001). Similarly, 79% of experts agreed that the evidence supported that statement in 1989,
whereas 11 years later 65% of experts agreed that high levels of stress impaired the accuracy of
eyewitness testimony. These surveys among experts suggest that consensus concerning the
stress-memory relationship has been declining over the years. However, the statement used in
previous surveys does not include an indication of memory phase (i.e., encoding or retrieval).
Additionally, the most recent survey investigating expert opinions on this relationship is nearly
two decades old (Kassin et al., 2001), and many studies regarding stress and memory have been
published since then. For example, all 90 papers included in the Shields et al. (2017) meta-
analysis on this topic were published in or after 2001, highlighting the need for a more
contemporary assessment of opinion.
Other surveys focused on beliefs about emotional events. For example, in one survey
80% of layperson respondents endorsed the notion that emotional events are usually remembered
BELIEFS ABOUT STRESS AND MEMORY
7
more accurately than memories for everyday events (Conway et al., 2014). More recently, 54%
of a surveyed lay sample agreed or strongly agreed that experiences involving very strong
emotions and memories of emotionally negative experiences were more accurately remembered
than emotionally moderate or weak, neutral, or positive experiences (Akhtar et al., 2018). The
finding that most laypeople believe that emotional intensity gives rise to accurate memories
seems to be out of line with other surveys indicating that laypeople generally believe acute stress
harms eyewitness memory. However, although emotional intensity and stress often relate to
similar applied matters, the two cannot be fully equated. For example, eyewitness scenarios often
involve both negative emotionality and stress (e.g., witnessing an unexpected fatal car accident
or life-threatening assault). Other experiences, however, may be emotionally negative, but not
necessarily elicit an acute stress response (e.g., a failed relationship or the death of an ill parent).
The relationship between emotional intensity and memory accuracy has also been investigated in
one expert sample (Akhtar et al., 2018). Forty-six percent of experts agreed or strongly agreed
with the idea that emotional experiences were more accurately remembered than neutral or
positive experiences. However, 54% of experts disagreed with this statement suggesting a similar
lack of consensus between experts regarding topics associated with the effects of acute stress on
memory.
Past surveys investigating stress and memory have typically included a single statement
concerning the effects of acute stress on memory (i.e., Very high levels of stress impair the
accuracy of eyewitness testimony). However, the complexity of the effects of acute stress on
memory cannot be meaningfully captured in this single item. A more in-depth investigation of
laypeople’s and experts’ understandings about effects of stress on memory is valuable for two
reasons. First, the complexity of this particular topic is evident through the numerous moderators
about which beliefs have not yet been examined. Specifically, previous surveys have not
BELIEFS ABOUT STRESS AND MEMORY
8
included questions about specificity of stressor timing (i.e., encoding vs. retrieval; see Joëls et
al., 2011; Quaedflieg & Schwabe, 2018), the neuroscientific theories behind stress effects on
memory, and the potential moderators of the acute stress-memory relationship (i.e., age, type of
memory test, stress severity, detail type, etc.). Understanding expert beliefs about these
moderators will also elucidate which factors require further investigation, setting important
directions for future research on this topic. Second, understandings about stress and memory can
have real life consequences. Laypeople’s views may enter the legal decision-making process
when they act as jurors, and research suggests their beliefs can impact their decisions about
credibility and guilt (Bornstein et al., 2008). Furthermore, experts’ opinions can also affect legal
decision-making when they testify as expert witnesses. Indeed, the effects of stress on the
accuracy of eyewitness testimony was identified as the topic second most frequently testified
about by experts across 21 eyewitness-related topics (Kassin et al., 1989). Therefore, even
though the different research fields focusing on stress and memory do not show conclusive
findings, understanding laypeople’s and expert’s beliefs with respect to this topic is still vital due
to these potential real-world consequences.
The Current Survey
The current survey assessed laypeople’s and experts’ beliefs about the relationship
between acute stress and memory. The survey items used are presented in Table 2. We targeted a
group of lay respondents and two groups of expert respondents, eyewitness memory researchers
and fundamental memory researchers (i.e., those investigating basic memory processes). We
examined beliefs using a variety of statements concerning the effects of stress on memory. The
primary interest of this exploratory survey was to examine what experts from both fields and
laypeople believe about these statements. We did not make explicit specific predictions for the
survey about current laypeople’s and experts’ beliefs.
BELIEFS ABOUT STRESS AND MEMORY
9
Method
Participants
We did not conduct a typical power analysis to determine sample size for two reasons: (i)
we did not have specific hypotheses for this exploratory survey and (ii) the pool of experts is,
naturally, constrained due to the specific nature of expertise. Thus, we based the number of
participants on our expected expert response rate estimating with respect to an initial list of
experts in relevant areas. We anticipated that we would obtain responses from around 50
eyewitness experts and 50 fundamental memory experts. In the event that such numbers were not
forthcoming, our stopping rule was to continue collection for as long as feasible. We planned to
recruit a similar number of laypeople, thus aiming for at least 100 layperson participants between
the ages of 18 and 65 to best reflect age range in a group of potential American jurors. The
survey was pre-registered on OSF
(https://osf.io/b93px?view_only=f83715544c4640c79c3fbfa50d996154). Table 3 presents the
demographic information for both the final laypeople and expert samples.
Exclusion criteria. We included four attention checks. Specifically, within the
instructions, we informed participants that at the end of the survey, they would be asked to
choose a shape and that they should select triangle. In addition, we included three unrelated
mock statements with a clear answer (e.g., Most humans live more than two hundred years). We
excluded participants who failed more than one attention check. Participants were also excluded
if they completed the survey in under 3 minutes. On average, laypeople completed the survey in
9.21 min (SD = 6.64) and experts in 23.37 min (SD = 19.21)
1
.
1
Result reported here excludes three outliers in the expert group (152 hours, 16 hours, and 10 hours) who likely left
the survey tab open on their computer during completion over one or several days.
BELIEFS ABOUT STRESS AND MEMORY
10
Laypeople. We recruited 129 American participants using Amazon Mechanical Turk (M-
Turk), an online crowdsourcing marketplace. M-Turk has been shown to be a viable platform for
academic data collection when compared with other commonly used platforms (Kees et al.,
2017). We selected this platform due to the ease and speed of data collection, but also to reach a
broad sample of individuals who may indeed be potential jurors (i.e., the general American
public). We excluded 20 laypeople because they did not pass three of the four attention checks (n
= 15), they were older than our cutoff age of 65 (n = 4), or they completed the survey too quickly
(n = 1), leaving us with a layperson sample of N = 109. Laypersons were thanked and received
$1 as compensation. These data were collected within one week in September 2019.
Experts. Following earlier surveys (Kassin et al., 1989, 2001), we contacted eligible
experts that we identified by perusing the pertinent literature to find those who had published
peer-reviewed papers on this topic (i.e., eyewitness and fundamental memory research related to
stress and memory). To do so, we searched for combinations of related terms (e.g., stress,
arousal, emotional better remembered, memory, eyewitness, etc.) on relevant databases (e.g.,
PsycInfo). Additionally, we examined publications referenced in larger meta-analyses examining
stress effects on memory (e.g., Deffenbacher et al., 2004; Shields et al., 2017). Finally, we
separately made a list of experts in the field of stress and memory and searched for additional
research that was published by them related to emotion/stress/arousal and memory. We sent one
initial email and two follow-up emails to 150 researchers over a four-month period between May
and September 2019. Additionally, we contacted members of the Society for Applied Research
on Memory and Cognition, the European Association of Psychology and Law, the American
Psychology-Law Society, and the Stress-NL Consortium
2
through server emails, explicitly
2
We did not originally include the Stress-NL Consortium in our pre-registered plan for survey dissemination, but
decided to distribute the survey to this organization due to its contact with current stress experts.
BELIEFS ABOUT STRESS AND MEMORY
11
requesting participation from those who had published peer-reviewed articles on the topic of the
effects of stress, arousal, or emotion on memory. The survey was closed in November 2019, after
over six months of data collection through these multiple avenues. Out of participants responding
to the expert survey, eight did not pass the attention checks and one participant asked to
withdraw their data post-survey.
These self-reported experts received additional demographic questions about their
research (see Table 3). Of the final sample, 89% possessed a Doctorate degree and the other 11%
held a Master’s degree, with 66% of experts expressing the effects of arousal/stress on memory
as a primary area of interest. Additionally, these experts had published in scientific journals, law
reviews, books, chapters, magazines, or newsletters (Mdn = 27, IQR = 68, range = 0 to 557),
many of which focused specifically on the effects of stress on memory (Mdn = 4, IQR = 10,
range = 0 to 400).
3
Nearly 29% of experts had acted as an expert witness, sometimes testifying
specifically about the effects of stress on memory (Mdn = 5, IQR = 20, range = 0 to 500).
If experts classified their primary area of research as eyewitness memory, applied
memory in forensic contexts, or other related forensic psychological areas, we assigned them to
the eyewitness memory expert group. If experts classified their primary area of research as the
neuroscience of memory or another memory or related psychological area, we assigned them to
the fundamental memory expert group. Two independent researchers categorized the unclassified
research areas, resulting in a high degree of reliability (Koo & Li, 2016), ICC (intraclass
correlation coefficient; absolute agreement, 2-way mixed-effects model) = .866, 95% CI from
.709 to .942, F (21, 21) = 13.952, p < .001. Disagreements (n = 1) between coders were resolved
through discussion. Of the final sample (N = 73), 37 were eyewitness experts and 36
3
Analyses were also conducted without the participant reporting zero publications (n = 1) and those with missing
numerical responses (n = 2), and results remained the same.
BELIEFS ABOUT STRESS AND MEMORY
12
fundamental memory experts. Experts were thanked upon completion but received no
reimbursement.
Materials
Survey. We created the survey using the online platform Qualtrics (Qualtrics, Provo,
UT), with separate versions for laypeople and experts. Both survey versions and datasets are
accessible on the OSF, with expert demographic information removed to protect confidentiality
(https://osf.io/jpra2/?view_only=a87bc3abda8c4cb699299ecfc9cc94d2). After consenting,
participants completed the survey in a self-paced format. They were unable to return to any of
the questions once they had continued the survey. For each statement, we created a shorthand
term for brevity; Table 2 presents these shorthands alongside each statement.
Layperson and expert statements. Both survey versions contained the same 21
statements related to the effects of acute stress on (eyewitness) memory. The first fixed statement
was a word-for-word reproduction of the single item used in past expert surveys (Kassin et al.,
1989, 2001) for comparison purposes (i.e., Very high levels of stress impair the accuracy of
eyewitness testimony). We also generated a list of topics relevant to the stress-memory
relationship that may be pertinent for eyewitness-related scenarios and are often discussed in
relevant reviews or papers (i.e., Christianson, 1992; Deffenbacher et al., 2004; Shields et al.,
2017, Shields, 2020). As such, the 20 other statements were generated with reference to past
theories or findings about potential effects or moderators of effects or were otherwise relevant to
eyewitness-related settings. Specifically, the random-order statements addressed specific issues
related to stressor timing on the stress-memory relationship, potential moderators of the stress-
memory relationship (e.g., type of memory test, age, role, detail type, stimulus type, stimulus
valence), and other areas of interest to the eyewitness field (e.g., misinformation effects, memory
specificity, relation to repressed memories). Some of the statements better agreed with the state
BELIEFS ABOUT STRESS AND MEMORY
13
of the science (e.g., stress impairs retrieval; see Shields et al., 2017), others were less established
(e.g., children less affected, see Deffenbacher et al., 2004, for a discussion), debated (e.g., stress
enhances encoding) or overlooked in past research (e.g., short crime).
We asked experts and laypeople to rate each statement from a list of options. Similar to
past surveys (e.g., Akhtar et al., 2018; Magnussen et al., 2010; Read & Desmarais, 2009), experts
and laypeople chose from one of five options: strongly disagree, somewhat disagree, somewhat
agree, strongly agree, or don’t know. Instructions at the beginning of the survey discouraged
guessing and clarified to experts that a don’t know choice was appropriate when the current
research in the field is inconclusive. For the final analysis, answers were collapsed and coded as
disagree (strongly disagree and somewhat disagree) and agree (strongly agree and somewhat
agree; cf. Benton et al., 2006; Read & Desmarais, 2009). Table A in the supplementary materials
shows the distribution of results across all five response categories.
Additional expert statements and questions. The expert version of the survey contained
eight additional random-order statements relating to more technical and fundamental topics
likely to be unknown and unsuitable for a layperson sample. These statements were generated
with reference to current neurobiological theories regarding acute stress effects on memory (e.g.,
Diamond et al., 2007; Joëls et al., 2006; Quaedflieg & Schwabe, 2018). Specifically, the
statements focused on the most relevant physiological stress responses, addressing the precise
roles that the autonomic nervous system and glucocorticoid activity play within the stress-
memory relationship.
Additionally, for each statement, we asked experts a) if they believed the statement was
reliable enough for psychologists to present in courtroom testimony (yes or no; court reliability),
b) if their opinion was based on published, peer reviewed, and scientific research (yes or no;
research basis), and c) if they would say that most lay people believe the statement to be true as
BELIEFS ABOUT STRESS AND MEMORY
14
a matter of common sense (yes, no, or don’t know; common sense). Tables B and C in
supplementary materials show responses to these additional questions.
Data Analyses
To address our research questions, we compared (i) expert responses to past expert
survey findings, (ii) eyewitness experts to fundamental memory expert responses, and (iii)
layperson to expert responses. We conducted a chi-square test between the two groups for each
relevant comparison: endorsements, referring to whether participants agreed or disagreed with
each statement and selections, referring to whether participants agreed/disagreed or selected
don’t know. We preregistered that we would use a Bonferroni correction and set the alpha to
.0017 (.05/29) to correct for multiple comparisons. However, to better preserve power, we
instead used a Holm-Bonferroni correction (Holm, 1979) by adjusting p-values based on the
number of tests and comparing with an alpha of .05.
Results
Comparison with Past Work
Following Benton et al. (2006), we compared the proportion of experts who agreed that
the statement Very high levels of stress impair the accuracy of eyewitness testimony was reliable
enough for psychologists to present in court with data from a past expert survey that used the
same statement (Kassin et al., 2001). Although 19 years have passed since the 2001 survey, there
is a chance that some of the same experts participated in both surveys, which would violate the
assumption of independence for a chi-square test. It is not possible to tell whether this is the case,
but due to the possibility, we present the results of this preregistered chi-square comparison with
caution. The current level of endorsement (61% of experts; i.e., 43 of 71) was similar to the
previous survey (60%, i.e., 37 of 62; Kassin et al., 2001), and these endorsement rates did not
differ statistically significantly from one another, χ2 (1, N = 133) = 0.011, p = .917, φ = .009.
BELIEFS ABOUT STRESS AND MEMORY
15
Eyewitness Experts versus Fundamental Memory Experts
Table 2 presents expert responses and for each statement, categorized by research field.
Figure 1 provides a visual overview of agreement rates for each statement between the three
groups. We first compared eyewitness memory experts and fundamental memory experts on
endorsements (i.e., whether they agreed or disagreed with each statement). Table 4 shows the
inferential statistics for these comparisons. A statistically significantly difference between groups
(φ = .462) emerged for only one statement, stress enhances encoding. A greater proportion of
fundamental memory experts (77.8%) than eyewitness memory experts (32.4%) agreed with the
idea that stress experienced during encoding enhances memory.
For this statement, we also explored relevant data for notable descriptive findings. First,
we looked at the broader breakdowns of responses across all five categories (reported in Table A
in supplementary materials). The majority of the fundamental memory group selected somewhat
agree (63.9%), with the rest selecting strongly agree (13.9%) or somewhat disagree (19.4%),
and only one electing don’t know (2.8%). On the other hand, eyewitness experts showed a wider
distribution: 8.1% selected strongly agree, 24.3% somewhat agree, 37.8% somewhat disagree,
24.3% strongly disagree, and 5.4% don’t know. Although the main difference between the
groups is clear, examining these broader responses shows the variability in the answers from
eyewitness experts in particular. Additionally, we descriptively examined proportions for stress
enhances encoding only for experts who reported that they had previously testified in court (n =
21, of which 18 were eyewitness memory experts and 3 were fundamental memory experts).
These experts were mostly eyewitness memory experts (85.7%), and we still see large diversity
in responding to stress enhances encoding in this subgroup. Specifically, experts who had
previously testified in court were split on their responses to stress enhances encoding: 14.3%
BELIEFS ABOUT STRESS AND MEMORY
16
strongly agreed, 23.8% somewhat agreed, 42.9% somewhat disagreed, and 19.0% strongly
disagreed.
We next examined group differences between eyewitness memory experts and
fundamental memory experts on selections (i.e., whether they selected don’t know compared to
agree or disagree; see Table D in supplementary materials). Eight statements differed
statistically significantly between groups: misinformation protection (φ = .385), primarily ANS
activity (φ = .374), ANS facilitates (φ = .434), rapid cortisol is beneficial (φ = .487), slow
cortisol is detrimental (φ = .436), glucocorticoid alone (φ = .397), HPA & ANS activated (φ =
.399), and HPA & ANS retrieval (φ = .443). For each of these statements, a greater proportion of
eyewitness memory experts selected don’t know than fundamental memory experts.
Laypeople versus Experts
Table 2 presents layperson responses for each statement. Table 5 shows the inferential
statistics for the endorsement comparisons between laypeople and experts. The two groups
differed statistically significantly in their responses to eight of the statements. A greater
proportion of laypeople agreed with the statements compared to experts for six of these
statements: children less affected (φ = .301), faces affected differently (φ = .416), professionals
less affected (φ = .506), repression (φ = .756), short crime (φ = .396), and misinformation
protection (φ = .355). For detail type (φ = .316) and moderate stress (φ = .366), a greater
proportion of experts agreed with the statements compared to laypeople.
For these statistically significant statements, we also descriptively examined responses on
a broader scale (Table A) to explore noteworthy differences. For example, although 20.2% of
laypeople selected strongly agree for faces affected differently, the majority of experts stuck with
a middle category (somewhat agree: 23.3%, somewhat disagree: 28.8%) or selected don’t know
(35.6%), highlighting the lack of strong expert beliefs about this statement. In addition, 0% of
BELIEFS ABOUT STRESS AND MEMORY
17
experts strongly agreed on professionals less affected, while around a quarter of laypeople
expressed this extreme agreement (26.6%). Similarly, for repression, 4.1% of experts but 33.9%
of laypeople selected strongly agree, while 57.5% of experts and 1.8% of laypeople selected
strongly disagree. Examining the extreme ends of the broader response scale highlights the
extent of the dissimilarity between groups for these statements.
We also examined differences between layperson and expert selections (see Table E in
supplementary materials). For only one statement did the distribution differ statistically
significantly between groups, indicating that a greater proportion of experts selected don’t know
for the older adults less affected statement than laypeople, χ2 (1, N = 182) = 16.88, p < .001, φ =
.305.
Discussion
In this survey study, we gathered beliefs from memory experts and laypeople related to
the effects of stress on eyewitness memory. We were primarily interested in proportions of each
group who agreed, disagreed, or selected don’t know for each statement (Table 2). Additionally,
we compared endorsements and selections between groups. In line with previous surveys, we
found that most experts in this sample strongly endorsed the belief that high levels of stress
impair the accuracy of eyewitness testimony (e.g., Kassin et al., 1989, 2001, Yarmey & Jones,
1983). In addition, both groups strongly endorsed the statement that stress during retrieval
impairs memory, which is in line with findings from fundamental research (e.g., Shields et al.,
2017; Wolf, 2017). However, when examining more specific statements in regard to encoding
(stress enhances encoding) and retrieval (stress impairs retrieval), we saw a divergence between
eyewitness and fundamental memory experts. Fundamental memory experts generally agreed
that experiencing stress at encoding enhances memory, whereas eyewitness memory experts did
not.
BELIEFS ABOUT STRESS AND MEMORY
18
Prior research examining the effects of stress during encoding on memory is mixed, with
different results often emerging across research fields (e.g., Davis et al., 2019; Deffenbacher et
al., 2004, vs. Henckens et al., 2009; Hoscheidt et al., 2004; Vogel & Schwabe, 2016). These
contrasting findings perhaps account for the contradictory understandings about the effects of
encoding stress on memory that emerged in this survey, and are likely due to methodological
differences between the research fields. Fundamental memory research tends to use robust
experimental methodology including validated laboratory stressors to induce acute stress (e.g.,
Trier Social Stress Test, Kirschbaum et al., 1993), physiological and subjective manipulation
checks to confirm stress inductions, and sufficient retention intervals between sessions (i.e., at
least 24-hours) to distinguish the stress effects of encoding and retrieval on memory
performance. However, these fundamental studies often examine memory performance for more
basic types of stimuli (e.g., word lists, static pictures; Schwabe et al., 2008; Smeets et al., 2007;
Zoladz et al., 2011).
On the other hand, eyewitness memory laboratory research uses unvalidated stressors
such as violent videos, electric shocks, or self-reports (e.g., Brigham et al., 1983; Clifford &
Hollin, 1981; Kramer et al., 1990; Bailis & Mueller, 1981). Additionally, many eyewitness
experiments rely only on self-reported stress as a manipulation check for the stress induction
(e.g., Buckhout et al., 1974; Davis et al., 2019). Indeed, as pointed out by Sauerland et al (2016),
only seven studies included in the Deffenbacher et al (2004) meta-analysis report physiological
stress measures. Subjective reports of stress, however, do not always correlate with physiological
acute stress responses (Hellhammer & Schubert, 2012). Eyewitness field studies show similar
limitations, failing to confirm HPA-axis activation (i.e., by examining cortisol) or lacking a
sufficient retention interval to specifically examine effects of encoding stress on memory
performance (e.g., Hope et al., 2016; Hulse & Memon, 2006; Morgan et al., 2004; Valentine &
BELIEFS ABOUT STRESS AND MEMORY
19
Mesout, 2008). The single session designs often used in eyewitness memory research make it
impossible to isolate the effects of encoding stress on different memory phases (i.e.,
consolidation versus retrieval; Sauerland et al., 2016; Thomas & Karanian, 2019).
Many of these methodological differences between fields stem from the distinct goals of
each particular research field. While the fundamental memory field often aims to examine the
basic neurobiological activities underlying the stress-memory relationship, the eyewitness
memory field is more interested in the impact that acute stress can have on memory for a crime
in applied witness contexts. Thus, the eyewitness memory field notably attempts to mimic
witness experiences. However, in such applied experiments, isolating stress effects can be
difficult, sometimes leading to a mischaracterization and overgeneralization of the term acute
stress (i.e., a physiological response involving HPA axis activation, as defined in the
fundamental memory field). Stemming from these unique research aims, the varied methodology
between fields likely contributes to the contrasting results, and perhaps explains why experts
from the two fields often express opposing views about how encoding stress affects memory
performance. This divergence in perspectives suggests an absence of interactions between
research fields. Critically, understanding results from fundamental memory studies that use more
precise methodology might be useful for eyewitness experts. Eyewitness researchers examining
the effects of stress on memory performance should strive to gain knowledge about the
fundamental stress literature and the methodological gold standards (see Shields, 2020), and
should also aim to collaborate with fundamental stress experts. In addition, fundamental memory
researchers could conduct research alongside or in consultation with eyewitness memory
researchers to produce work that better reflects conditions in the real world, for example by using
more ecologically valid scenarios (e.g., mock crimes).
Expert Beliefs about Moderators Between Encoding Stress and Memory
BELIEFS ABOUT STRESS AND MEMORY
20
To better parse responses to the more general statements about encoding stress effects on
memory performance, we also probed for experts’ beliefs about potential moderating factors that
may affect the relationship between encoding stress and memory. Many of the statements that
showed low levels of expert endorsement (i.e., below 50%; abstractness, faces affected
differently, violent events, children less affected, older adults less affected) have not been
thoroughly empirically tested. For example, although some findings indicate that children
(Deffenbacher et al., 2004) or older adults (Hidalgo et al., 2019; Smith et al., 2019) may be less
affected by stress than younger adults, the vast majority of studies have focused solely on
younger adults. Therefore, the lack of consensus and higher levels of don’t know responses are in
line with available research findings. These data may help guide future research by emphasizing
some of the moderators that need to be further examined with empirical work. However, some
statements received high levels of endorsement despite ambiguity in research findings. There are
conflicting findings regarding differences in stress effects on victims versus bystander
eyewitnesses (e.g., Kassin, 1984; Hope et al., 2016; Hosch & Bothwell, 1990), yet most of the
eyewitness memory experts and fundamental memory experts endorsed the idea that a victim’s
memory will be more affected by encoding stress (victims more affected). Similarly, the vast
majority of both expert groups disagreed that stress experienced during a short crime will not
affect memories (short crime), although we have not been able to identify any empirical research
conducted on this specific topic. Furthermore, both groups generally agreed that eyewitnesses
who experience moderate levels of stress during a crime display better levels of memory than
those who experience low levels of stress (moderate stress). Most experts from both groups also
endorsed the idea that severe but not moderate levels of stress generally harm eyewitness
memory (severe stress). Neuroscientific research supports this inverted-U shape idea, which
suggests poorer cognitive performance at low and high levels of stress and better performance at
BELIEFS ABOUT STRESS AND MEMORY
21
medium levels of stress (e.g., Abercrombie et al., 2003; de Kloet et al., 1999; Lupien et al.,
2007). This inverted-U might also explain the different findings between the eyewitness and
fundamental memory fields. For example, some fundamental memory research suggests that
stress induced in the laboratory during encoding enhances stressor-related memory (e.g., Vogel
& Schwabe, 2016), while field studies have found impairments in stressor-related memory (e.g.,
Metcalfe et al., 2019). Although research directly supporting the statements discussed in this
section is not substantial, experts might have drawn from relevant theories to support their
choices on these topics (e.g., dual mode model, temporal dynamics model, Yerkes-Dodson law;
Diamond et al., 2007; Joëls et al., 2006; Yerkes & Dodson, 1908). Empirical work on these
generally endorsed but under-researched topics would also be beneficial for understanding the
intricacies of the stress-memory relationship.
Other relevant factors endorsed by experts have a more solid research evidence-base. For
example, both expert groups agreed that emotional stressful experiences are remembered better
than non-emotional ones (emotional better remembered), an account supported by research
(Cahill et al., 2003; Kuhlmann et al., 2005; Shields et al., 2017, but see Schwabe et al., 2008;
Shermohammed et al., 2019). Additionally, both agreed that encoding stress enhances memory
for central details and undermines memory for peripheral details (detail type). These opinions are
generally supported by research that suggests simultaneous helping and harming effects of stress
on different types of details (Christianson, 1992; Christianson & Loftus, 1987; Heuer &
Reisberg, 1990, but see Lanciano & Curci, 2011; Wessel et al., 2000). Eyewitness memory
experts likely related this statement to the weapon focus effect (e.g., Kramer et al., 1990; Loftus
et al., 1987), a phenomenon demonstrating that eyewitness memory for faces and other details is
poorer if a weapon was present during a crime (Fawcett et al., 2013). Finally, the majority of
both groups disagreed that those who experience stress are more likely to have repressed
BELIEFS ABOUT STRESS AND MEMORY
22
memories than those who do not (repression), which is in fact not supported by empirical data
(e.g., Otgaar et al., 2019).
Expert Beliefs about Moderators between Retrieval Stress and Memory
We also examined factors relevant to stress effects at memory retrieval. The majority of
experts who agreed that retrieval stress impairs memory also endorsed a more applied version of
this statement, though to a lesser extent. This more applied statement (police interview) stems
logically from the broader statement (stress impairs retrieval), though specific research has not
yet been conducted on this topic. Other retrieval-related statements were based on limited prior
research. For example, some research suggests that free recall is impaired more than recognition
ability by stress before retrieval (test type; de Quervain et al., 2000, 2003; Gagnon & Wagner,
2016), a statement generally endorsed by both groups. Some experimental results also suggest
that if memory is tested immediately after a stressor, memory is not harmed but rather sometimes
even enhanced (immediate retrieval enhances; Schönfeld et al., 2014; Schwabe & Wolf; 2014).
However, less than a third of both expert groups agreed. Finally, around two thirds of eyewitness
memory experts and one third of fundamental memory experts believed that memory tested two
hours after a stressor will be worse than memory tested 30 minutes after a stressor (retrieval
timing), a statement based on some limited results (e.g., Schwabe & Wolf, 2014). These
statements have some basis in research but lack a substantial literature, which may explain the
absence of expert consensus in this sample.
Expert Beliefs on Neuroscientific Statements
Experts answered eight additional statements about neuroscientific explanations of stress
effects on memory. These statements were mostly based on theoretical research (e.g., Diamond
et al., 2007; Joëls et al., 2006; Joëls et al., 2011; Quaedflieg & Schwabe, 2018; Roozendaal,
2002; Schwabe et al., 2012) that delineate the specific timing and roles autonomic nervous
BELIEFS ABOUT STRESS AND MEMORY
23
system and glucocorticoid activity play in the relationship between stress and memory. Overall,
eyewitness memory experts selected don’t know more often than fundamental memory experts
for each statement. This disparity between expert groups suggests that eyewitness memory
experts understand less about the neuroscience behind the stress-memory relationship. That
being said, perhaps most striking in regard to the eight neuroscientific statements was the
proportion of don’t know selections across both groups of experts. Over a third of fundamental
experts also selected don’t know for most of the neuroscientific statements. Some statements had
a more limited research basis, including statements about how noradrenergic stimulation and
glucocorticoid activation act specifically alone or together to affect brain networks related to
memory (noradrenergic alone, glucocorticoid alone, HPA & ANS activated). Other statements
were more established (see Joëls et al., 2006; Quaedflieg & Schwabe, 2018), but did not receive
a majority endorsement from fundamental memory experts (slow cortisol is detrimental, HPA &
ANS retrieval). The proportion of don’t know selections indicate a lack of knowledge in this
research area, suggesting that certain topics are not yet established and accepted by an expert
majority – at least in these two research domains.
A majority of fundamental memory experts did generally show consensus on three
statements, which point towards research findings that are more accepted. Fundamental memory
experts mostly disagreed that effects of stress on memory are primarily driven by autonomic
nervous system activity, though nearly all agreed that encoding is facilitated when the autonomic
nervous system is activated while experiencing an emotional event such as a crime. Additionally,
most fundamental memory experts agreed that rapid non-genomic glucocorticoids have a
beneficial effect on memory formation. Considering that 78% of fundamental memory experts
agreed that experiencing encoding stress enhances memory, these endorsements of
neuroscientific explanations of encoding enhancements are perhaps unsurprising.
BELIEFS ABOUT STRESS AND MEMORY
24
Layperson Beliefs about Stress Effects on Memory
As juror opinions about stress effects on memory can also enter the courtroom and may
affect decision-making (Bornstein et al., 2008), we examined laypeople’s responses and
compared them to experts’ responses. In line with experts, most laypeople agreed that high levels
of stress impair eyewitness testimony (high stress impairs). In contrast to experts, only about a
third of laypeople believed that moderate levels of stress at encoding could enhance memory
compared to low levels of stress (moderate stress). Thus, laypeople tend to view stress as
overwhelmingly negative, with any degree of stress in any memory phase generally impairing
memory.
Other differences between laypeople’s and experts’ responses point towards diverging
opinions of the public, including the controversial belief that stress causes repressed memories
(repression, 85%), which research suggests is not the case (e.g., Otgaar et al., 2019).
Additionally, the majority of laypeople believed that police officers’ memories are resistant to
stress effects while eyewitness and fundamental memory experts did not (professionals less
affected), a view more in line with the limited research on this topic (e.g., Stanny & Johnson,
2000). Finally, laypeople also believed that stress affects faces differently than other types of
stimuli (faces affected differently) contrasting lower endorsement levels from eyewitness
memory experts and fundamental memory researchers on this under-researched and inconclusive
topic.
Whereas expert beliefs are generally formed from research on these topics in academic
settings, laypersons’ beliefs likely stem from intuitive feelings or perceptions about each
statement. Given that stress is generally viewed as a negative experience (e.g., Adams, 2016;
Becker, 2013), it is unsurprising that laypeople seem to view any degree of stress as harmful, in
contrast with expert opinion. Laypeople’s agreement that police officers’ memories can
BELIEFS ABOUT STRESS AND MEMORY
25
withstand stress is also an evident erroneous but understandable commonsense belief (e.g., Hope,
2016; Stanny & Johnson, 2000). A related statement used in past surveys showed that low
percentages of laypeople (28% and 39%) endorsed the idea that Police officers and other trained
observers are no more accurate as eyewitnesses than is the average person (e.g., N = 111,
Benton et al., 2006; N = 79, Kassin & Barndollar, 2001, respectively). Taken together, these
responses suggest that many laypeople believe that professionals are generally better
eyewitnesses who are less influenced by external factors such as stress. Two recent surveys also
show that large proportions of participants (59% and 67%, respectively) endorsed the idea that
traumatic experiences can be unconsciously repressed for many years and then recovered (N =
230 and N = 79; Otgaar et al., 2019), a statement similar to repression in our survey. Factors
such as television and media may influence such beliefs. For example, 75% of students (N = 613)
who reported hearing about someone recovering a repressed memory said they heard about such
a circumstance though television (Golding et al., 1996). Additionally, amount of media exposure
to information about repressed memories was positively correlated with beliefs in repressed
memories. Thus, perhaps the endorsement of the idea that stress causes repressed memories from
laypeople in this sample originally stemmed from media or television exposure. To sum up, as
demonstrated in this survey and previous surveys, commonsense beliefs do not always align with
expert assessments concerning what the contemporary science suggests (e.g., Benton et al., 2006;
Simons & Chabris, 2011).
Implications for Applied Legal Settings
These data serve as an initial empirical attempt of expert and layperson beliefs about the
effects of acute stress on memory performance. Although agreement between expert groups was
observed on several statements, the most striking difference between groups pertained to the
statement that stress enhances encoding (φ = .462), where fundamental memory experts mostly
BELIEFS ABOUT STRESS AND MEMORY
26
agreed and eyewitness memory experts mostly disagreed. From an exploratory analysis, we also
saw a descriptive split among experts who had testified in court. That is, not all testifying experts
fell on one side of the belief (i.e., agreeing vs. disagreeing with the statement that stress
enhances encoding). These results further support the idea that different expert witnesses bring
different views into the courtroom. In this way, jurors and judges could hear contrasting
statements from opposing expert witnesses, or hear from only one expert witness, who could fall
on either side of the belief. If an expert witness strongly endorses the idea that encoding stress
enhances memory, jurors could assume that testimony provided by an eyewitness who
experienced stress is highly reliable. If an expert witness reports the opposite, jurors may
unreasonably disregard the testimony of an eyewitness who experienced stress. Thus, for
seemingly irresolute statements such as stress enhances encoding, exercising caution in the
courtroom is important.
On the other hand, these data also suggest that jurors already likely bring their own
conceptions about the effects of stress on memory performance into the courtroom.
Understanding these pre-existing commonsense beliefs is crucial for knowing where expert
witness knowledge is needed. For example, if laypeople assume that any amount of stress will
automatically impair memory, they may view the testimony from a stressed eyewitness as
lacking in probative value. This could later affect their legal decisions. Similarly, if laypeople are
unaware of how stress can affect the memories of professionals such as police officers, they may
give too much credence to their testimonies over others. For topics like these that show greater
consensus from experts in general, reports from an expert witness could be particularly valuable
in the courtroom.
Limitations and Future Directions
BELIEFS ABOUT STRESS AND MEMORY
27
There are a number of limitations associated with the current survey. Some nuance is lost
when using closed statements with an agree/disagree response format that force respondents to
‘choose a side’. Particularly, responding to broad statements (e.g., high stress impairs, stress
enhances encoding, stress impairs retrieval, etc.) that use wide-ranging terms such as “memory”
can be challenging. That is, “memory” could be thought of quite generally, for example knowing
that an experience occurred (e.g., ability to remember gist or central information) or much more
specifically (e.g., ability to remember detailed or peripheral information). For this reason, we
included several other statements to provide us with more insight into potential moderators that
could explain differences in how the broader statements were answered (e.g., severe stress, detail
type, abstractness, etc.). With these more specific statements, we believe that, in contrast to
previous surveys, we were better able to interpret the results than if we used broad
generalizations alone. Future research could explore the use of a less rigid method such as a
qualitative survey or perhaps focus groups, to examine the specific circumstances in which
experts believe stress enhances, impairs, or does not affect memory.
A potential limitation pertaining to the layperson group is that the statements might have
been too technical for them. We initially addressed this by leaving out the technical
neuroscientific statements for the lay sample (i.e., items 22-29), and by explicitly defining
certain memory jargon such as terms like encoding and retrieval. However, other terms may
have also been too technical for them to fully understand the statements, such as understanding
the meaning behind central vs. peripheral details or free recall vs. recognition. Given the
laypeople’s responses for these statements, it does not seem that much concern is warranted,
although future research should aid layperson understanding as much as possible in surveys.
Our expert sample size is comparable to past expert surveys (e.g., Kassin et al., 1989,
2001). Nonetheless, analyses comparing expert groups might be underpowered due to the limited
BELIEFS ABOUT STRESS AND MEMORY
28
number of experts who were involved in the survey. Obtaining this expert sample was difficult
due to the inherently limited population, and we collected expert data for six months using
multiple channels and repeated calls in an attempt to access the largest sample possible. We also
attempted to reduce the Type 1 error by using a Holm-Bonferroni correction. With a final sample
of 73 experts, the between-expert comparisons are only powered to detect large effects (80%
powered to detect Cohen’s w = .50), whereas the expert-layperson analyses (n = 182) are
powered to detect medium and large samples (80% powered to detect Cohen’s w = .30). Thus,
results should be interpreted with caution, keeping the limited sample size and number of
comparisons in mind. Specifically, owing to the reduced power, non-statistically significant
differences may have been due to an inability detect smaller effect sizes, and the statistically
significant differences may be overestimated. On the other hand, large effects may be most
relevant for real world application in this area.
In addition to a greater number of experts, a more comprehensive representation of
possible experts would also benefit future research. Our study examined only a subsection of
potential experts: academics who investigate stress effects on memory or related topics. Nearly a
third of experts in this survey have experience acting as expert witnesses in court. However,
other categories of people who also testify in court settings as experts (e.g., clinical
psychologists) may not publish on these matters. This survey did not include those various
groups, and thus, our definition of expert is restrained to those working and publishing in
academic contexts.
The results from this survey might serve as a beneficial guide for future research in this
area. Statements that experts answered with don’t know or where agree and disagree selections
were divided may indicate areas that need to be better investigated. These areas include factors
such as age differences (children less affected, older adults less affected), specificity of stressor
BELIEFS ABOUT STRESS AND MEMORY
29
timing (immediate retrieval enhances, retrieval timing), factors at encoding (violent events,
moderate stress), and the form of remembered information (test type, faces affected differently).
The results also show the continuing need for fundamental neuroscientific research about how
biological stress responses affect memory formation and retrieval in humans. Finally, we suggest
that academic experts should be aware of research that exists across the wider research domain,
particularly if they plan to testify in court on these matters.
Conclusion
This survey explored contemporary experts’ and laypeople’s beliefs about the effects of
stress on memory encoding and retrieval. Only five statements (i.e., high stress impairs, stress
impairs retrieval, police interview, detail type, and short crime) out of 29 received consensus
levels of over 75% among both eyewitness and fundamental memory expert groups. As such,
these results appear to indicate a general lack of consensus about most factors that play a role in
the stress-memory relationship. However, the two expert groups only statistically differed from
each other regarding the enhancing effects of encoding stress on memory. Examining beliefs
about other factors, such as stress severity and type of remembered detail, provided some insight
into this disparity. Laypeople differed from experts on some factors and endorsed some ideas
that are not supported by empirical research, for example, that trained professionals such as
police are less affected by stress and that stress causes repressed memories. In summary, results
from this survey suggest that whereas some factors have a wide consensus among experts, there
may be significant gaps in this literature where more research is needed to enhance our
understanding of the relationship between stress and memory.
BELIEFS ABOUT STRESS AND MEMORY
30
Open Practices Statement
This survey study was pre-registered. The pre-registration is available at
https://osf.io/b93px?view_only=f83715544c4640c79c3fbfa50d996154. The data and materials
for the study are available at
https://osf.io/jpra2/?view_only=a87bc3abda8c4cb699299ecfc9cc94d2.
Funding Information
This research was supported by a fellowship awarded from the Erasmus Mundus Joint
Doctorate Program [blinded for review] with Framework Partnership Agreement (FPA) 2013-
0036 and Specific Grant Agreement (SGA) 532473-EM-5-2017-1-NL-ERA MUNDUS-EPJD to
[blinded for review].
BELIEFS ABOUT STRESS AND MEMORY
31
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Note. % endorsed = percentage of participants who believed in negative effects of high stress on eyewitness memory. Potential jurors =
general public. * = Statement in this survey was “if an eyewitness was under high stress at the time of the crime, the eyewitness will have
better recall for the details of the event”, percentage in table represents those who believed this statement was false.
Table 1
Percentage of Layperson Respondents Agreeing With the Statement on the Negative Effects of High Stress on Eyewitness Memory in Past
Surveys
Authors
Year
Country
Sample
% endorsed
Loftus
1979
USA
500 students
67
Yarmey & Jones
1983
Canada
60 students and 60 local adults
57
Deffenbacher & Loftus
1982
USA
76 students
85
Deffenbacher & Loftus
1982
USA
100 students
79
Deffenbacher & Loftus
1982
USA
46 jurors
41
Deffenbacher & Loftus
1982
USA
43 jurors
53
Noon & Hollin
1987
UK
28 students
79
Noon & Hollin
1987
UK
24 law students
79
Noon & Hollin
1987
UK
24 potential jurors
67
Kassin & Barndollar
1992
USA
39 students and 40 local adults
82
Schmechel, O’Toole, Easterly, & Loftus*
2004
USA
1,007 potential jurors
80
Benton, Ross, Bradshaw, Thomas, & Bradshaw
2006
USA
111 jurors
68
Read & Desmarais
2009
Canada
201 potential jurors
79
Read & Desmarais
2009
Canada
200 potential jurors
92
Read & Desmarais
2009
Canada
598 potential jurors
88
Magnussen, Melinder, Stridbeck, & Raja
2010
Norway
164 members of juror pool
79
Magnussen, Melinder, Stridbeck, & Raja
2010
Norway
1,000 potential jurors
84
4,321 participants
79.15
(3,420 participants)
BELIEFS ABOUT STRESS AND MEMORY
44
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
1. Very high levels of stress impair the
accuracy of eyewitness testimony.
high stress
impairs
Agree
Disagree
Don’t know
94.6 (87.3, 100.0)
2.7 (0.0, 7.9)
2.7 (0.0, 7.9)
80.6 (67.7, 93.5)
16.7 (4.5, 28.9)
2.8 (0.0, 8.2)
93.6 (89.0, 98.2)
3.7 (0.2, 7.2)
2.8 (0.0, 5.9)
2. If an eyewitness is stressed during a
police interview (i.e., at retrieval), his or
her memory will be less accurate than if
he or she were not stressed.
police interview
Agree
Disagree
Don’t know
81.1 (68.5, 93.7)
8.1 (0.0, 16.9)
10.8 (0.8, 20.8)
75.0 (60.9, 89.1)
13.9 (2.6, 25.2)
11.1 (0.8, 21.4)
81.7 (74.4, 89.0)
12.8 (6.5, 19.1)
5.5 (1.2, 9.8)
3. Experiencing stress while trying to
remember something (i.e., at retrieval)
impairs memory retrieval.
stress impairs
retrieval
Agree
Disagree
Don’t know
86.5 (75.5, 97.5)
2.7 (0.0, 7.9)
10.8 (0.8, 20.8)
91.7 (82.7, 100.0)
8.3 (0.0, 17.3)
0.0
78.0 (70.2, 85.8)
12.8 (6.5, 19.1)
9.2 (3.8, 14.6)
4. Experiencing stress during an event (i.e.,
at encoding) enhances memory for that
event.
stress enhances
encoding
Agree
Disagree
Don’t know
32.4 (17.3, 47.5)
62.2 (46.6, 77.8)
5.4 (0.0, 12.7)
77.8 (64.2, 91.4)
19.4 (6.5, 32.2)
2.8 (0.0, 8.2)
33.9 (25.0, 42.8)
53.2 (43.8, 62.6)
12.8 (6.5, 19.1)
BELIEFS ABOUT STRESS AND MEMORY
45
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
5. Children’s memories are less affected by
stress experienced during an event (i.e.,
at encoding) than adults’ memories.
children less
affected
Agree
Disagree
Don’t know
5.4 (0.0, 12.7)
73.0 (58.7, 87.3)
21.6 (8.3, 34.9)
2.8 (0.0, 8.2)
55.6 (39.4, 71.8)
41.7 (25.6, 57.8)
27.5 (19.1, 35.9)
56.9 (47.6, 66.2)
15.6 (8.8, 22.4)
6. Stress experienced during an event (i.e.,
at encoding) enhances memory for
central details of the event, but not for
peripheral details.
detail type
Agree
Disagree
Don’t know
78.4 (65.1, 91.7)
10.8 (0.8, 20.8)
10.8 (0.8, 20.8)
80.6 (67.7, 93.5)
16.7 (4.5, 28.9)
2.8 (0.0, 8.2)
45.0 (35.7, 54.3)
35.8 (26.8, 44.8)
19.3 (11.9, 26.7)
7. When an eyewitness is stressed while
trying to remember something (i.e., at
retrieval), his or her free recall ability is
more negatively affected by this stress
than his or her recognition ability.
test type
Agree
Disagree
Don’t know
56.8 (40.8, 72.8)
18.9 (6.3, 31.5)
24.3 (10.5, 38.1)
72.2 (57.6, 86.8)
8.3 (0.0, 17.3)
19.4 (6.5, 32.3)
75.2 (67.1, 83.3)
10.1 (4.4, 15.8)
14.7 (8.1, 21.3)
8. Stress affects memory for faces
differently than memory for other types
of stimuli.
faces affected
differently
Agree
Disagree
Don’t know
37.8 (22.2, 53.4)
32.4 (17.3, 47.5)
29.7 (15.0, 44.4)
19.4 (6.5, 32.3)
38.9 (23.0, 54.8)
41.7 (25.6, 57.8)
64.2 (55.2, 73.2)
11.9 (5.8, 18.0)
23.9 (15.9, 31.9)
BELIEFS ABOUT STRESS AND MEMORY
46
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
9. The memory of trained professionals,
such a police officers, will be less
affected by stress than the memory of
normal eyewitnesses.
professionals less
affected
Agree
Disagree
Don’t know
13.5 (2.5, 24.5)
86.5 (75.5, 97.5)
0.0
19.4 (6.5, 32.3)
72.2 (57.6, 86.8)
8.3 (0.0, 17.3)
64.2 (55.2, 73.2)
29.4 (20.8, 38.0)
6.4 (1.8, 11.0)
10. A victim’s memory will typically be
more affected by stress experienced
during a crime (i.e., at encoding) than a
bystander eyewitness’ memory.
victims more
affected
Agree
Disagree
Don’t know
75.7 (61.9, 89.5)
18.9 (6.3, 31.5)
5.4 (0.0, 12.7)
58.3 (42.2, 74.4)
19.4 (6.5, 32.3)
22.2 (8.6, 35.8)
78.9 (71.2, 86.6)
12.8 (6.5, 19.1)
8.3 (3.1, 13.5)
11. Eyewitnesses who experience stress
during a crime are more likely to have
memories that they unconsciously
blocked due to trauma (i.e., “repressed
memories”) than those who do not
experience such stress.
repression
Agree
Disagree
Don’t know
16.2 (4.3, 28.1)
75.7 (61.9, 89.5)
8.1 (0.0, 16.9)
13.9 (2.6, 25.2)
69.4 (54.3, 84.5)
16.7 (4.5, 28.9)
85.3 (78.7, 91.9)
7.3 (2.4, 12.2)
7.3 (2.4, 12.2)
12. Eyewitnesses have more difficulty
remembering violent events than non-
violent ones.
violent events
Agree
Disagree
Don’t know
40.5 (24.7, 56.3)
54.1 (38.0, 70.2)
5.4 (0.0, 12.7)
13.9 (2.6, 25.2)
55.6 (39.4, 71.8)
30.6 (15.5, 45.7)
44.0 (34.7, 53.3)
36.7 (27.7, 45.7)
19.3 (11.9, 26.7)
BELIEFS ABOUT STRESS AND MEMORY
47
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
13. Stressful experiences that are emotional
are generally better remembered than
stressful experiences that are not
emotional.
emotional better
remembered
Agree
Disagree
Don’t know
62.2 (46.6, 77.8)
18.9 (6.3, 31.5)
18.9 (6.3, 31.5)
61.1 (45.2, 77.0)
22.2 (8.6, 35.8)
16.7 (4.5, 28.9)
52.3 (42.9, 61.7)
29.4 (20.8, 38.0)
18.3 (11.0, 25.6)
14. Eyewitnesses who experience moderate
levels of stress during a crime (i.e., at
encoding) display better memory than
eyewitnesses who experience low levels
of stress during a crime.
moderate stress
Agree
Disagree
Don’t know
62.2 (46.6, 77.8)
18.9 (6.3, 31.5)
18.9 (6.3, 31.5)
69.4 (54.3, 84.5)
16.7 (4.5, 28.9)
13.9 (2.6, 25.2)
35.8 (26.8, 44.8)
50.5 (41.1, 59.9)
13.8 (7.3, 20.3)
15. Severe levels of stress, but not moderate
levels of stress, generally harm
eyewitness memory.
severe stress
Agree
Disagree
Don’t know
83.8 (71.9, 95.7)
16.2 (4.3, 28.1)
0.0
63.9 (48.2, 79.6)
22.2 (8.6, 35.8)
13.9 (2.6, 25.2)
63.3 (54.3, 72.3)
23.9 (15.9, 31.9)
12.8 (6.5, 19.1)
16. When an eyewitness experiences a
relatively short crime (i.e., fewer than
five minutes), his or her memories are
not affected by this stress.
short crime
Agree
Disagree
Don’t know
2.7 (0.0, 7.9)
91.9 (83.1, 100.0)
5.4 (0.0, 12.7)
0.0
91.7 (82.7, 100.0)
8.3 (0.0, 17.3)
26.6 (18.3, 34.9)
54.1 (44.7, 63.5)
19.3 (11.9, 26.7)
BELIEFS ABOUT STRESS AND MEMORY
48
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
17. If one experiences stress during an event
(i.e., at encoding), it is likely that his or
her memories will be more abstract and
general rather than specific and detailed.
abstractness
Agree
Disagree
Don’t know
37.8 (22.2, 53.4)
35.1 (19.7, 50.5)
27.0 (12.7, 41.3)
41.7 (25.6, 57.8)
52.8 (36.5, 69.1)
5.6 (0.0, 13.1)
57.8 (48.5, 67.1)
24.8 (16.7, 32.9)
17.4 (10.3, 24.5)
18. If memory is immediately tested after a
stressor, one does not experience a
memory deficit; rather, memory at this
stage can actually be enhanced.
immediate
retrieval enhances
Agree
Disagree
Don’t know
29.7 (15.0, 44.4)
37.8 (22.2, 53.4)
32.4 (17.3, 47.5)
22.2 (8.6, 35.8)
41.7 (25.6, 57.8)
36.1 (20.4, 51.8)
46.8 (37.4, 56.2)
31.2 (22.5, 39.9)
22.0 (14.2, 29.8)
19. Memory tested two hours after a stressor
is experienced will be worse than
memory tested 30 minutes after a stressor
is experienced.
retrieval timing
Agree
Disagree
Don’t know
62.2 (46.6, 77.8)
16.2 (4.3, 28.1)
21.6 (8.3, 34.9)
30.6 (15.5, 45.7)
44.4 (28.2, 60.6)
25.0 (10.9, 39.1)
57.8 (48.5, 67.1)
23.9 (15.9, 31.9)
18.3 (11.0, 25.6)
20. Stress that occurs before the presentation
of incorrect information can protect an
eyewitness’ original memory because
stress prevents new information from
being incorporated into existing memory.
misinformation
protection
Agree
Disagree
Don’t know
10.8 (0.8, 20.8)
43.2 (27.2, 59.2)
45.9 (29.8, 62.0)
19.4 (6.5, 32.3)
69.4 (54.3, 84.5)
11.1 (0.8, 21.4)
45.9 (36.5, 55.3)
30.3 (21.7, 38.9)
23.9 (15.9, 31.9)
BELIEFS ABOUT STRESS AND MEMORY
49
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
21. Memories of older adults (aged 55+) are
less affected by stress experienced during
an event (i.e., at encoding) than
memories of younger adults (aged 18-
35).
older adults less
affected
Agree
Disagree
Don’t know
5.4 (0.0, 12.7)
43.2 (27.2, 59.2)
51.4 (35.3, 67.5)
8.3 (0.0, 17.3)
47.2 (30.9, 63.5)
44.4 (28.2, 60.6)
22.0 (14.2, 29.8)
58.7 (49.5, 67.9)
19.3 (11.9, 26.7)
22. Effects of stress on memory are driven
primarily by autonomic nervous system
activity.*
primarily ANS
activity
Agree
Disagree
Don’t know
37.8 (22.2, 53.4)
13.5 (2.5, 24.5)
48.6 (32.5, 64.7)
27.8 (13.2, 42.4)
58.3 (42.2, 74.4)
13.9 (2.6, 25.2)
23. Encoding is facilitated when the
autonomic nervous system is activated
while experiencing an emotional event
such as a crime.*
ANS facilitates
Agree
Disagree
Don’t know
48.6 (32.5, 64.7)
13.5 (2.5, 24.5)
37.8 (22.2, 53.4)
94.4 (86.9, 100.0)
2.8 (0.0, 8.2)
2.8 (0.0, 8.2)
24. Rapid non-genomic glucocorticoids have
a beneficial effect on memory formation
for an event such as a crime.*
rapid cortisol is
beneficial
Agree
Disagree
Don’t know
13.5 (2.5, 24.5)
2.7 (0.0, 7.9)
83.8 (71.9, 95.7)
52.8 (36.5, 69.1)
11.1 (0.8, 21.4)
36.1 (20.4, 51.8)
BELIEFS ABOUT STRESS AND MEMORY
50
Table 2
Survey Statements About Stress and Memory With Percentage of Participant Endorsement
Statement
Shorthand
Percentage of participant endorsement
Eyewitness memory experts
n = 37
Fundamental memory experts
n = 36
Laypeople
n = 109
25. Slow genomic glucocorticoids have a
detrimental effect on memory formation
for an event such as a crime.*
slow cortisol is
detrimental
Agree
Disagree
Don’t know
13.5 (2.5, 24.5)
2.7 (0.0, 7.9)
83.8 (71.9, 95.7)
27.8 (13.2, 42.4)
30.6 (15.5, 45.7)
41.7 (25.6, 57.8)
26. At encoding, noradrenergic stimulation
alone can be sufficient for enhancing the
connectivity and excitability within brain
networks related to memory.*
noradrenergic
alone
Agree
Disagree
Don’t know
21.6 (8.3, 34.9)
10.8 (0.8, 20.8)
73.0 (58.7, 87.3)
41.7 (25.6, 57.8)
19.4 (6.5, 32.3)
38.9 (23.0, 54.8)
27. At encoding, glucocorticoid actions alone
can be sufficient for enhancing the
connectivity and excitability within brain
networks related to memory.*
glucocorticoid
alone
Agree
Disagree
Don’t know
16.2 (4.3, 28.1)
0.8 (0.8, 20.8)
73.0 (58.7, 87.3)
30.6 (15.5, 45.7)
36.1 (20.4, 51.8)
33.3 (17.9, 48.7)
28. To observe the effects of stress during
encoding on memory, both the
autonomic nervous system and the HPA
axis must be activated at the same time.*
HPA & ANS
activated
Agree
Disagree
Don’t know
16.2 (4.3, 28.1)
8.1 (0.0, 16.9)
75.7 (61.9, 89.5)
27.8 (13.2, 42.4)
36.1 (20.4, 51.8)
36.1 (20.4, 51.8)
29. When noradrenergic arousal interacts
with non-genomic glucocorticoids during
retrieval, memory is typically impaired.*
HPA & ANS
retrieval
Agree
Disagree
Don’t know
13.5 (2.5, 24.5)
0.0
86.5 (75.5, 97.5)
44.4 (28.2, 60.6)
11.1 (0.8, 21.4)
44.4 (28.2, 60.6)
Note. * = statement presented only to expert sample. Agree = somewhat agree + strongly agree. Disagree = somewhat disagree + strongly disagree. Numbers
in parentheses = 95% CIs (lower, upper).
BELIEFS ABOUT STRESS AND MEMORY
51
Note. * = multiple choices possible. ** = one response missing.
Table 3
Overview of Survey Participants’ Demographics
Age
Gender
Race/ethnicity*
Nationality
Education
Legal system involvement
Laypeople
N = 109
M = 37.52
SD = 10.82
Range: 19 to 65
53.2% male
45.0% female
0.9% nonbinary
0.9% prefer not to
say
82.6% White
8.3% Hispanic, Latino, or Spanish
origin
5.5% Black or African American
6.4% Asian
0.9% American Indian or Alaskan
Native
100% American
57.8% Bachelor’s
26.6% High school
11.0% Master’s
3.7% Other (e.g.,
Associate’s degree or
some college)
Been on a jury:
15.6%
Witnessed a crime:
34.9%
(n = 21 for violent crime,
n = 17 for non-violent crime)
Of these, 34.2% (n = 13) directly
involved in criminal justice
system
Experts
N = 73
M = 46.07
SD = 15.95
Range: 26 to 87
50.7% male
46.6% female
2.7% prefer not to
say
94.5% White
2.7% Hispanic, Latino, or Spanish
origin
1.4% Asian
1.4% Middle Eastern or North
African
2.7% prefer not to say
64.4% American
11.0% German
9.6% Dutch
5.5% British
2.7% Australian
1.4% Danish
1.4% Canadian
1.4% Spanish
1.4% Italian
1.4% French
89.0% Doctorate
11.0% Master’s
Degree in:
91.8% Psychology
5.5% Other science
2.7% Medicine
Acted as expert witness**:
69.9% Never
28.8% More than once
BELIEFS ABOUT STRESS AND MEMORY
52
Table 4
Inferential Statistics for 2 x 2 χ2 Tests Comparing Endorsements (Agree versus Disagree) in Eyewitness
and Fundamental Memory Experts (df = 1)
Statement
n
χ2
p
Adjusted
p
φ
1. High stress impairs*
71
.055
.084
.241
2. Police interview*
65
.475
.084
.099
3. Stress impairs retrieval*
69
.615
.084
.113
4. Stress enhances encoding
70
14.933
< .001
< .001
.462
5. Children less affected*
50
> .999
.084
.044
6. Detail type*
68
.735
.084
.071
7. Test type*
57
.179
.084
.193
8. Faces affected differently
47
1.978
.160
.084
.205
9. Professionals less affected
70
0.728
.394
.084
.102
10. Victims more affected
63
0.225
.635
.084
.060
11. Repression
64
0.011
.917
.084
.013
12. Violent events
60
3.429
.064
.084
.239
13. Emotional better remembered
60
0.089
.766
.084
.038
14. Moderate stress
61
0.144
.704
.084
.049
15. Severe stress
68
0.949
.330
.084
.118
16. Short crime*
68
> .999
.084
.119
17. Abstractness
61
0.361
.548
.084
.077
18. Immediate retrieval enhances
48
0.426
.514
.084
.094
19. Retrieval timing
56
8.720
.003
.084
.395
20. Misinformation protection*
52
> .999
.084
.022
21. Older adults less affected*
22. Primarily ANS activity
23. ANS facilitates*
24. Rapid cortisol is beneficial*
25. Slow cortisol is detrimental*
26. Noradrenergic alone*
27. Glucocorticoid alone
28. HPA & ANS activated*
29. HPA & ANS retrieval*
38
50
58
29
27
33
34
32
25
8.099
0.567
> .999
.004
.032
> .999
.182
> .999
.452
.433
.549
.084
.084
.084
.084
.084
.084
.084
.084
.084
.057
.402
.303
.008
.299
.047
.129
.209
.218
Note. Adjusted p = Holm-Bonferroni adjustment for multiple comparisons. Bold = adjusted p
significant at the .05 level. * = Fisher’s exact test instead of chi-square test (when expected cell sizes <
5).
BELIEFS ABOUT STRESS AND MEMORY
53
Table 5
Inferential Statistics for 2 x 2 χ2 Tests Comparing Endorsements (Agree versus Disagree) in Experts
and Laypeople (df = 1)
Statement
n
χ2
p
Adjusted
p
φ
1. High stress impairs*
177
> .999
.078
.124
2. Police interview
168
0.058
.810
.078
.019
3. Stress impairs retrieval
168
2.959
.085
.078
.133
4. Stress enhances encoding
165
5.361
.021
.078
.180
5. Children less affected
142
12.857
< .001
< .001
.301
6. Detail type
156
15.613
< .001
< .001
.316
7. Test type
150
0.959
.327
.078
.080
8. Faces affected differently
130
22.472
< .001
< .001
.416
9. Professionals less affected
172
44.109
< .001
< .001
.506
10. Victims more affected
163
1.837
.175
.078
.106
11. Repression
165
94.295
< .001
< .001
.756
12. Violent events
148
6.463
.011
.078
.209
13. Emotional better remembered
149
1.992
.158
.078
.116
14. Moderate stress
155
20.789
< .001
< .001
.366
15. Severe stress
163
0.984
.321
.078
.078
16. Short crime
156
24.480
< .001
< .001
.396
17. Abstractness
151
7.704
.006
.078
.226
18. Immediate retrieval enhances
134
5.612
.018
.078
.205
19. Retrieval timing
145
1.575
.210
.078
.104
20. Misinformation protection
135
19.721
< .001
< .001
.382
21. Older adults less affected
126
2.984
.084
.078
.154
Note. Adjusted p = Holm-Bonferroni adjustment for multiple comparisons. Bold = adjusted p
significant at the .05 level. * = Fisher’s exact test instead of chi-square test (when expected cell sizes <
5).
BELIEFS ABOUT STRESS AND MEMORY
54
Figure 1
Survey Statements About Stress and Memory With Percentage of Participant Endorsement and 95% Confidence Intervals
BELIEFS ABOUT STRESS AND MEMORY
55
Figure 1
Survey Statements About Stress and Memory With Percentage of Participant Endorsement and 95% Confidence Intervals
BELIEFS ABOUT STRESS AND MEMORY
56
Figure 1
Survey Statements About Stress and Memory With Percentage of Participant Endorsement and 95% Confidence Intervals
Note. Error bars represent 95% confidence intervals.
