eyewitness memory psychology essay

Eyewitness Testimony in Psychology

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Eyewitness testimony is a legal term that refers to an account given by people of an event they have witnessed.

For example, they may be required to describe a trial of a robbery or a road accident someone has seen. This includes the identification of perpetrators, details of the crime scene, etc.

Eyewitness testimony is an important area of research in cognitive psychology and human memory.

Juries tend to pay close attention to eyewitness testimony and generally find it a reliable source of information. However, research into this area has found that eyewitness testimony can be affected by many psychological factors:

Anxiety / Stress Reconstructive Memory Weapon Focus Leading Questions ( Loftus and Palmer, 1974 )

Anxiety / Stress

Anxiety or stress is almost always associated with real-life crimes of violence. Deffenbacher (1983) reviewed 21 studies and found that the stress-performance relationship followed an inverted-U function proposed by the Yerkes-Dodson Curve (1908).

This means that for tasks of moderate complexity (such as EWT), performance increases with stress up to an optimal point where it starts to decline.

Clifford and Scott (1978) found that people who saw a film of a violent attack remembered fewer of the 40 items of information about the event than a control group who saw a less stressful version. As witnessing a real crime is probably more stressful than taking part in an experiment, memory accuracy may well be even more affected in real life.

However, a study by Yuille and Cutshall (1986) contradicts the importance of stress in influencing eyewitness memory.

They showed that witnesses of a real-life incident (a gun shooting outside a gun shop in Canada) had remarkable accurate memories of a stressful event involving weapons. A thief stole guns and money, but was shot six times and died.

The police interviewed witnesses, and thirteen of them were re-interviewed five months later. Recall was found to be accurate, even after a long time, and two misleading questions inserted by the research team had no effect on recall accuracy. One weakness of this study was that the witnesses who experienced the highest levels of stress where actually closer to the event, and this may have helped with the accuracy of their memory recall.

The Yuille and Cutshall study illustrates two important points:

1. There are cases of real-life recall where memory for an anxious / stressful event is accurate, even some months later. 2. Misleading questions need not have the same effect as has been found in laboratory studies (e.g. Loftus & Palmer).

Reconstructive Memory

Bartlett’s theory of reconstructive memory is crucial to an understanding of the reliability of eyewitness testimony as he suggested that recall is subject to personal interpretation dependent on our learned or cultural norms and values, and the way we make sense of our world.

Many people believe that memory works something like a videotape. Storing information is like recording and remembering is like playing back what was recorded. With information being retrieved in much the same form as it was encoded.

However, memory does not work in this way. It is a feature of human memory that we do not store information exactly as it is presented to us. Rather, people extract from information the gist, or underlying meaning.

In other words, people store information in the way that makes the most sense to them. We make sense of information by trying to fit it into schemas, which are a way of organizing information.

Schemas are mental “units” of knowledge that correspond to frequently encountered people, objects or situations. They allow us to make sense of what we encounter in order that we can predict what is going to happen and what we should do in any given situation. These schemas may, in part, be determined by social values and therefore prejudice.

Schemas are, therefore capable of distorting unfamiliar or unconsciously ‘unacceptable’ information in order to ‘fit in’ with our existing knowledge or schemas. This can, therefore, result in unreliable eyewitness testimony.

Bartlett tested this theory using a variety of stories to illustrate that memory is an active process and subject to individual interpretation or construction.

In his famous study “War of the Ghosts”, Bartlett (1932) showed that memory is not just a factual recording of what has occurred, but that we make “effort after meaning”.

By this, Bartlett meant that we try to fit what we remember with what we really know and understand about the world. As a result, we quite often change our memories so they become more sensible to us.

His participants heard a story and had to tell the story to another person and so on, like a game of “Chinese Whispers”.

The story was a North American folk tale called “The War of the Ghosts”. When asked to recount the detail of the story, each person seemed to recall it in their own individual way.

With repeating telling, the passages became shorter, puzzling ideas were rationalized or omitted altogether and details changed to become more familiar or conventional.

For example, the information about the ghosts was omitted as it was difficult to explain, whilst participants frequently recalled the idea of “not going because he hadn’t told his parents where he was going” because that situation was more familiar to them.

For this research, Bartlett concluded that memory is not exact and is distorted by existing schema, or what we already know about the world.

It seems, therefore, that each of us ‘reconstructs’ our memories to conform to our personal beliefs about the world.

This clearly indicates that our memories are anything but reliable, ‘photographic’ records of events. They are individual recollections which have been shaped & constructed according to our stereotypes, beliefs, expectations etc.

The implications of this can be seen even more clearly in a study by Allport & Postman (1947).

When asked to recall details of the picture opposite, participants tended to report that it was the black man who was holding the razor.

Clearly this is not correct and shows that memory is an active process and can be changed to “fit in” with what we expect to happen based on your knowledge and understanding of society (e.g. our schemas).

Weapon Focus

This refers to an eyewitness’s concentration on a weapon to the exclusion of other details of a crime. In a crime where a weapon is involved, it is not unusual for a witness to be able to describe the weapon in much more detail than the person holding it.

Loftus et al. (1987) showed participants a series of slides of a customer in a restaurant. In one version, the customer was holding a gun, in the other the same customer held a checkbook.

Participants who saw the gun version tended to focus on the gun. As a result, they were less likely to identify the customer in an identity parade those who had seen the checkbook version

However, a study by Yuille and Cutshall (1986) contradicts the importance of weapon focus in influencing eyewitness memory.

Allport, G. W., & Postman, L. J. (1947). The psychology of rumor . NewYork: Holt, Rinehart & Winston.

Bartlett, F.C. (1932). Remembering: A Study in Experimental and Social Psychology . Cambridge: Cambridge University Press.

Clifford, B.R. and Scott, J. (1978). Individual and situational factors in eyewitness memory. Journal of Applied Psychology , 63, 352-359.

Deffenbacher, K. A. (1983). The influence of arousal on reliability of testimony. In S. M. A. Lloyd-Bostock & B. R. Clifford (Eds.). Evaluating witness evidence . Chichester: Wiley. (pp. 235-251).

Loftus, E.F., Loftus, G.R., & Messo, J. (1987). Some facts about weapon focus. Law and Human Behavior , 11, 55-62.

Yerkes R.M., Dodson JD (1908). The relation of strength of stimulus to rapidity of habit-formation. Journal of Comparative Neurology and Psychology , 18: 459–482.

Yuille, J.C., & Cutshall, J.L. (1986). A case study of eyewitness memory of a crime. Journal of Applied Psychology , 71, 291-301.

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Eyewitness memory.

John T. Wixted John T. Wixted University of California San Diego
https://doi.org/10.1093/acrefore/9780190236557.013.911
Published online: 22 March 2023

Eyewitness testimony during a criminal trial, even when made in good faith, is widely considered to be unreliable because (a) basic-science research has shown how malleable eyewitness memory can be and (b) many real-world wrongful convictions involve eyewitness misidentifications of innocent defendants. However, like other forms of forensic evidence, there are conditions under which declarations based on eyewitness memory are reliable and conditions under which they are unreliable. Precisely because memory is so malleable, declarations based on eyewitness memory are the most reliable on the first test conducted early in a police investigation. Indeed, the very act of testing memory changes (i.e., contaminates) memory, and this is true whether memory is tested by a police interview (recall of details) or by a police photo lineup (face recognition). For example, because of the contaminating effect of the first test, a witness who initially recalls a detail with low confidence is at risk of later recalling that same detail with higher confidence. Similarly, a witness who initially identifies a suspect from a photo lineup with low confidence is at risk of later identifying that same suspect with higher confidence. In addition, memory can be contaminated by extraneous factors that occur after the first test (e.g., conversations with other people), leading to higher confidence or even to an altogether different memory decision (e.g., initially claiming that a person well known to the witness was not the perpetrator but later remembering that he was). Unbeknownst to police investigators, any change in a witness’s good-faith memory of events after the first test is far more likely to reflect memory contamination than it is to reflect a more successful search of memory. Moreover, and critically, this is true no matter how the witness rationalizes the inconsistency (e.g., “I was nervous on the first test but then I calmed down and searched my memory more carefully, and now I am positive he is the perpetrator”). A witness has no awareness of the insidious effects of memory contamination and certainly has no scientific expertise in the underlying memory mechanisms involved. Therefore, asking why a witness’s memory-based declaration changed from one test to the next is a question for a memory expert, not an eyewitness. A memory expert can explain that the main problem with relying on eyewitness memory is not that it is unreliable. Instead, the main problem is that the criminal justice system ignores the results of the reliable first test of uncontaminated memory and instead relies on the results of subsequent unreliable tests of contaminated memory to win a conviction. Assuming good faith on the part of the eyewitness, this practice should be reversed by relying on the results of the first test of uncontaminated memory and ignoring all later tests, especially the maximally contaminated test of memory that occurs under oath at trial.

photo lineup
police interview
eyewitness memory reliability
memory contamination
confidence and accuracy

Is eyewitness memory reliable? In years gone by, the science-based answer to this question was an emphatic “no.” However, a large body of research has accumulated showing that eyewitness memory is a lot like other kinds of forensic evidence: There are conditions under which it is reliable and conditions under which it is unreliable. Therefore, instead of asking whether eyewitness memory is reliable, a better question to ask is the following: When is eyewitness memory reliable and when is it unreliable?

In the legal system, the answer to that question is ultimately a judgment call, one that scientists can inform but cannot make. Instead, for any given case, judges and juries ultimately make that call, ideally with guidance from science. The science-based story summarized here begins with a brief consideration of how memory works followed by a consideration of the two main ways that eyewitness memory can be tested, namely, by recall (a police interview) or by face recognition (an eyewitness identification procedure). Either way, it is important to distinguish between the conditions under which eyewitness memory provides useful information and the conditions under which it does not.

A Brief Tutorial on How Memory Works

At the time of the to-be-remembered experience, memories are formed when sensory information from different modalities (e.g., sights, sounds, smells) simultaneously activates distributed regions of the brain that are each specialized for processing modality-specific information. For example, visual aspects of the experience are initially processed by regions of the brain that are specialized for processing visual information, auditory aspects of the experience are initially processed by regions of the brain that are specialized for processing auditory information, and so on.

Aspects of the multisensory experience that command attention are encoded (i.e., a record is formed in the brain), whereas aspects of an experience that fall outside the focus of attention are not. Thus, encoded memories tend to be fragmentary, not complete representations of an experience. As an example, a witness might attend to the perpetrator’s face but not to what the perpetrator was wearing. In that case, a memory record of his face, but not his clothing, would be formed. Interestingly, according to standard principles of neuroscience, the memory record is formed in the same specialized region of the brain that processed the incoming sensory information ( Brodt & Gais, 2021 ). In this example, the face-processing neurons that are responsible for initially perceiving the face also create a memory record of that face.

Needless to say, after information is encoded, forgetting inevitably occurs. It might therefore seem obvious that the more time that goes by since the information was encoded (before memory is tested), the less reliable any remembered information will be. However, this, too, is a more nuanced story than intuition might suggest. As time goes by and forgetting occurs, less and less information about the crime will be remembered. In that sense, memory becomes less accurate over time. However, the main question of interest to triers of fact (judges and juries) concerns the reliability of any information that is still retained. Sometimes, that information remains reliable even after a long retention interval and sometimes it does not.

At the retrieval stage, memory is usually tested in one of two basic ways, namely, recall or recognition. In a recall test, the witness is asked to recollect details about the crime during a police interview. In a recognition test, the face of a suspect is presented to the witness as part of an eyewitness identification procedure, and the witness is asked whether or not this is the person who committed the crime. Although the principles of memory are similar in some respects for these two ways of testing memory, they also have some key differences, so they are best considered separately.

Testing Recall of Events Using an Interview

When asked to recall events (e.g., “tell me what happened, starting at the beginning”), a witness retrieves the fragmentary memory record while, at the same time, the brain unconsciously “fills in the blanks” with reasonable default assumptions about other details that were likely present at the time of encoding. Until the 1970s, it was generally assumed that such memories were reliable so long as they appeared to be honestly believed and had the qualities of true memories (e.g., they were detailed, confidently reported, and perhaps even accompanied by emotion). However, classic work by Elizabeth Loftus beginning in the 1970s began to change that perspective.

Memory Is Malleable

In early work, Loftus and Palmer (1974) found that altering a single suggestive word during the questioning of a witness can influence the witness’s memory for a video of a car crash. For example, asking “how fast were the cars going when they smashed into each other?” resulted in witnesses later (falsely) recalling broken glass much more often than asking “how fast were the cars going when they contacted each other?” A few years later, Loftus et al. (1978) reported that memory for the details of a traffic accident could be distorted by false post-event suggestion (e.g., the misleading suggestion of a stop sign when the witness actually saw a yield sign). Still later, Loftus and her colleagues found that it was possible to implant more elaborate false memories. For example, by providing misleading information, false memories have been implanted of being lost in a shopping mall ( Loftus & Pickrell, 1995 ), of spilling punch on the parents of the bride at a wedding ( Hyman & Billings, 1998 ), and of committing a crime ( Shaw & Porter, 2015 ; see also Shaw, 2018 ; Wade et al., 2018 ). False memories have also been implanted for being hospitalized overnight for an ear infection, for getting one’s hand caught in a mousetrap ( Lindsay et al., 2004 ), and for having received a skin graft as part of a routine medical procedure as a child ( Mazzoni & Memon, 2003 ).

Moral Panics Involving Apparently False Memories

The idea that memory is malleable initially caught the field by surprise, but the fact that detailed false memories can be unintentionally formed is now widely accepted. However, what came as a further surprise to the field in the 1980s and 1990s is the fact that it is even possible for detailed and seemingly believable memories of childhood sexual abuse to be completely false. In addition to basic laboratory research suggesting that nonsexual false memories are easy to create, two separate overreactions by the criminal justice system led to the painful realization that the same is true for highly detailed memories of childhood sexual abuse.

The McMartin Preschool Trial

The first overreaction is known as the “McMartin Preschool trial,” where daycare operators were charged with sexually abusing children under their care. The daycare operators were ultimately acquitted years later after it became clear that the highly detailed memories of sexual abuse (sincerely believed by the children and still believed by some of them now that they are adults) were almost certainly false, having been unintentionally implanted by well-intentioned investigators who repeatedly interviewed them ( Garven et al., 1998 ).

Recovered Memories of Childhood Sexual Abuse

The hope that an unintentionally suggestive interview technique might be a problem only when children were interviewed was dashed shortly thereafter. The second overreaction played out mostly in the 1990s and is sometimes referred to as the “repressed memory epidemic” ( Pendergrast, 2017 ). It was during this time that adult women, often in therapy, would recover long-forgotten memories of childhood sexual abuse. Upon recovering these long-forgotten memories, charges would be filed against the remembered perpetrators, and some were sent to prison based on nothing more than the recovered memory (i.e., with no independent corroborating evidence). In retrospect, it is easy to understand why these memories were considered reliable enough to determine that the alleged perpetrators were guilty. After all, the recovered memories were highly detailed, they seemed to be (and undoubtedly were) emphatically believed by the alleged victim, they were plausible, and they were often accompanied by high levels of emotion. In short, the witnesses appeared to be highly credible. However, because memory is now understood to be malleable, when memories are announced for the first time years after the fact, they cannot be regarded as presumptively reliable. They might be true, but they might be false, and that is the problem.

Structured Interviews

The realization that interviewers and therapists can elicit false recollections that distort memory from that point forward prompted research into what kinds of interview questions have that effect and how to elicit accurate information using better questions. This research found that improper interview technique includes, for example, (a) asking suggestive questions or otherwise introducing postevent misinformation (e.g., Loftus et al., 1978 ), (b) asking an abundance of closed-ended questions (vs. more appropriate open-ended questions; Lamb et al., 2007 ), and (c) encouraging witnesses to guess as opposed to more appropriately providing an option not to respond ( Earhart et al., 2014 ). To avoid problematic questions like these while eliciting as much accurate information as possible, structured interviews have now been developed. For children, the National Institute of Child Health and Human Development protocol ( Orbach et al., 2000 ) can be used to elicit accurate information without unintentionally contaminating memory in children. For adults, police departments can instead use the Cognitive Interview ( Fisher & Geiselman, 1992 ) or some variant of it. When such interview protocols are used early in a police investigation, what witnesses recall with high confidence tends to be quite accurate ( Wixted et al., 2018 ).

Whether or not a specific interview protocol is used, a report issued in 1999 by the Department of Justice provided general guidelines for how to interview a witness ( National Institute of Justice, 1999 ). In a section entitled “Section III: Procedures for Interviewing the Witness by the Follow-up Investigator,” the DOJ report recommended that during the interview, the investigator should do the following:

Encourage the witness to volunteer information without prompting.

Encourage the witness to report all details, even if they seem trivial.

Ask open-ended questions (e.g., “What can you tell me about the car?”); augment with closed-ended, specific questions (e.g., “What color was the car?”).

Avoid leading questions (e.g., “Was the car red?”).

Caution the witness not to guess.

Ask the witness to mentally recreate the circumstances of the event (e.g., “Think about your feelings at the time”).

Encourage nonverbal communication (e.g., drawings, gestures, objects).

Avoid interrupting the witness.

Encourage the witness to contact investigators when additional information is recalled.

Instruct the witness to avoid discussing details of the incident with other potential witnesses.

Encourage the witness to avoid contact with the media or exposure to media accounts concerning the incident.

Although a great deal of work has shed light on how to avoid the unintentional implantation of false memories when interviewing witnesses, it is not an easy skill to learn or maintain. The literature shows that someone who has been trained in the use of a structured interview and whose interviewing performance is monitored on a regular basis can obtain accurate information beyond what has been spontaneously reported by the witness. By contrast, interviewers who have not been trained and are not monitored on a regular basis are more likely to unintentionally elicit false information that risks contaminating memory. Price and Roberts (2011) summarized the problem as follows:

Warren et al. (1999) assessed the outcome of a 10-day training session in the U.S. that involved measuring both knowledge gain and interviewer behaviour change. Although interviewer knowledge about the content of the training was significantly increased following training, this newly acquired knowledge did not translate into a change in interviewer practices (see also Aldridge & Cameron, 1999 ; Freeman & Morris, 1999 ). The finding of increased knowledge, but a lack of behaviour change, is concerning and indicates that a simple knowledge assessment test following training is insufficient for determining training effectiveness.

Thus, mere knowledge of how to conduct an interview may not be enough. Proper interview technique appears to be a function of both training and then monitoring to ensure that a learned skill continues to be properly executed. In the absence of monitoring (with corrective feedback), interviewers tend to revert back to asking leading questions that can elicit false information.

Other Sources of Memory Contamination

It is important to also keep in mind that the memory test itself (involving improper interview technique) is not the only source of memory contamination. On the contrary, memory can be contaminated in a wide variety of ways. In this regard, consider some of the additional steps in the DOJ recommendations listed earlier (beyond interview technique) that are designed to avoid memory contamination, such as encouraging the witness to (a) avoid discussing details with other witnesses, (b) avoid contact with the media, and (c) avoid exposure to media accounts concerning the incident. These considerations underscore the importance of conducting a proper interview as soon as possible after the witnessed crime. Doing so minimizes the chances of memory contamination from independent sources (e.g., conversations with other witnesses, news reports, rumors).

Regardless of how memory is contaminated, once it happens, there is no way for the witness to know that it has happened and no way for anyone else to know it either. The reason is that false memories are subjectively experienced as true memories, and when they are described to others, they have all of the attributes of true memories. In a paper entitled “How to Tell If a Particular Memory Is True or False,” Bernstein and Loftus (2009) specifically addressed the striking similarities of true and false memories. They set up their analysis as follows:

Consider the following situation. Mary X sits on the witness stand in court, recounting an emotionally charged memory involving childhood sexual abuse. Her report is both detailed and emotional. She explains how her grandfather molested her and how she had repressed the event for many years before recovering the memory in therapy. Is Mary's report the result of a real memory or a product of suggestion or imagination or some other process? ( Bernstein & Loftus, 2009 , p. 370)

After reviewing the large body of scientific research that has addressed the question posed by the title of their paper, Bernstein and Loftus (2009) reached the following disconcerting conclusion: “If someone believes earnestly that he ate a large spider as a child, but in actuality he did not, how can we spot this falsehood? The simple, yet unsatisfying, answer is that we cannot determine this with certainty” (p. 370), and “the focus on single rich memories presently does not tell us whether a particular memory is true or false” (p. 373).

The qualities of the memories themselves cannot distinguish true from false memories; only independent corroborating evidence can verify if the memories are accurate. When tested by recall, memories of the distant past are not, in and of themselves, particularly diagnostic of the truth no matter how detailed they are, no matter how plausible they seem, no matter how sincerely believed they are, and no matter how much emotion they elicit. The reason is that there are many sources of contamination, and their effects simply cumulate over time. Therefore, the longer the retention interval (i.e., the more time has elapsed between encoding and retrieval), the more independent corroborating or disconfirming evidence is needed to determine whether the memories are true or false.

Even Recollections of Salient Events Become Less Reliable Over Time

The same basic principles emerged from a distinct line of memory research on the nature of forgetting. For example, in an influential study, Talarico and Rubin (2003) investigated memory for the terrorist attacks of September 11, 2001 . In their study, on September 12, 2001 , 54 participants were asked to record their memory of two events: (a) when they first heard about the terrorist attacks of September 11 and (b) a recent everyday event. They were tested again 1, 6, or 32 weeks later. Although “flashbulb memories” (i.e., memories of shocking events) are subjectively experienced as being forever etched in our brains, the accuracy of memories for the events of 9/11 declined over time in much the same way as the accuracy of memories for everyday events did. They differed only in that the decreasingly accurate memories of shocking events tended to be remembered with high confidence (despite the decline in accuracy), whereas the decreasingly accurate memories of everyday events were more appropriately remembered with decreasing confidence. The authors of this paper concluded that “Flashbulb memories are not special in their accuracy, as previously claimed, but only in their perceived accuracy.”

Precisely because confidently held memories evolve over time due to forgetting plus contamination, it is essential to test memory using a proper interview as soon as possible after the to-be-remembered event. Unfortunately, as time goes by, memories fade and can be contaminated in many ways, such as different witnesses talking to each other during everyday conversations, or seeing details about the event on the news or in the newspaper, or even just mentally rehearsing what might have happened. The latter phenomenon is known as “imagination inflation,” which refers to the fact that simply imagining an event increases the belief that it happened ( Garry & Polaschek, 2000 ; Mazzoni & Memon, 2003 ). For all of these reasons, the longer ago recalled events occurred, the less trustworthy those memories are, no matter how real they appear to be. Not only does the passage of time cause memories to weaken and provide more opportunity for contamination, but (as intuition suggests) the weaker memories become the more vulnerable they are to contamination (e.g., Baym & Gonsalves, 2010 ; Pezdek & Roe, 1995 ). This suggests that memories of very old events are especially susceptible to contamination.

Reminiscence

In another relevant line of research, studies have shown that under certain conditions, when someone is asked on more than one occasion to recall a prior event, information that they failed to recall on one test can be successfully recalled on a subsequent test. This phenomenon (i.e., recalling now what one failed to previously recall) can result in “hypermnesia,” which is an overall increase in the amount of accurately information recalled with successive testing (e.g., Scrivner & Safer, 1988 ). When that happens, it means that some information that was not recalled on the first test is recalled on a later test (a phenomenon known as “reminiscence”). However, and this is the key point, reminiscence has been observed when memory is tested soon after learning and when the interval of time between tests of memory is short. As reported by Wheeler and Roediger (1992) , “In general, when the intervals between successive tests are short, improvement occurs between tests. When these intervals are long, forgetting occurs” (p. 240). Indeed, as they further point out, when the intervals are long, “forgetting and distortion” due to the normal reconstructive processes of memory are to be expected. When sincerely recollected information emerges for the first time when memory is tested again long after the initial test, it raises concerns that the memory might be false. The most reliable information comes from tests conducted early in the police investigation, so the main focus should be placed on what is recollected at that time.

Testing Face Recognition Using a Photo Lineup

Eyewitness identification procedures are tests of face recognition memory. There are several different ways to conduct such tests, but the common denominator of all of them is that they involve a suspect, who is the person the police think may have committed the crime and who is either innocent or guilty. In an eyewitness identification procedure, the suspect’s face is shown to the eyewitness, who then decides whether or not this is the person who committed the crime. The suspect’s face can be tested either alone (a showup) or in a group (a lineup).

The simplest eyewitness identification procedure is known as a “showup,” where the police present a suspect to a witness for a yes/no decision about whether this is the person who committed the crime. A showup is often used soon after the police are called, while they are still actively processing a crime scene. For example, after canvassing the area, they might come across a suspect (e.g., someone who matches the description provided by the eyewitness) a few blocks away. The suspect is detained and brought to the witness, who is asked if this is the person who committed the crime. The key feature of this test is that it involves a single face. Although a showup usually involves an in-person test, memory is sometimes tested later in a police investigation using a single photo (“Is this the person who committed the crime?”). Such a single-photo test is also often referred to as a showup.

One long-standing concern about a showup is that it is inherently “suggestive” because the witness might reasonably conclude that the police have good reason to believe that this is the person who committed the crime. The witness might therefore identify the suspect on that basis alone, not because he matches the witness’s memory of the perpetrator. In technical terms, seeing a single face under suggestive conditions can induce a “response bias” (i.e., a tendency) to make an identification, whether the suspect strongly matches memory or not. For that reason, many believe that a less suggestive eyewitness identification procedure would be preferable.

An alternative eyewitness identification procedure is a lineup. A lineup consists of one suspect (who is either innocent or guilty) along with a number of physically similar “fillers” who are known to be innocent. When presented with a lineup, the witness can (a) identify the suspect, (b) identify a filler, or (c) reject the lineup. Live lineups were once the norm, but, according to a survey conducted in 2013 , photo lineups are used by the large majority of police departments ( Police Executive Research Forum, 2013 ). The photos can be presented all at once (a simultaneous lineup) or they can be presented one at a time for individual yes/no decisions (sequential lineup). One advantage of a well-constructed lineup is that it is much less suggestive than a showup because no single person stands out as the one who the police suspect as having committed the crime.

Conducting a Proper Lineup Procedure

Of course, a lineup is better than a showup only if it is properly constructed and properly administered. Recommendations on how to construct and administer a proper lineup have grown over the years and now include (a) selecting fillers who (at a minimum) match the witness’s description of the perpetrator, (b) including at least five fillers, (c) using a blind lineup administrator (i.e., an administrator who does not know the identity of the suspect), (d) instructing the witness that the perpetrator may or may not be present in the lineup, (e) recording an immediate confidence statement if the witness makes an identification (this applies to a showup as well), and (f) videotaping the entire procedure (see Wells et al., 2020 , for still more recommendations). Lineups are superior to showups not only because they are less suggestive but also because they enhance the ability of eyewitnesses to discriminate (i.e., tell the difference between) innocent and guilty suspects. What does that mean, exactly?

Lineups Increase Discriminability

Using a showup, imagine that out of every 100 innocent suspects, 20 are misidentified (false alarm rate = 20/100 = .20), and out of every 100 guilty suspects, 80 are correctly identified (hit rate = 80/100 = .80). However, using a lineup, imagine that only five out of every 100 innocent suspects are misidentified (false alarm rate = 5/100 = .05), and out of every 100 guilty suspects, 60 are correctly identified (hit rate = 60/100 = .60). This difference between the two procedures—that is, the lower hit and false alarm rates associated with a lineup compared to a showup—reflects a phenomenon known as “filler siphoning” ( Colloff et al., 2018 ; Smith et al., 2018 ); that is, identifications are made to fillers that might otherwise have been made to innocent or guilty suspects. The more fillers there are in a lineup, the lower both the hit rate and the false alarm rate to suspects will be due to filler siphoning.

Next imagine changing the showup procedure in such a way as to lower its false alarm rate to .05 as well (matching that of a lineup). This might be achieved, for example, by instructing witnesses tested using a showup not to make an identification unless they are 100% certain of being correct. Once the two procedures have been equated with respect to the false alarm rate, are they now diagnostically equivalent? That depends on their respective hit rates under the same conditions.

Using the showup procedure in conjunction with the new instruction not to make an identification in the absence of 100% certainty, the hit rate might now be reduced to .50 (from .80 without using that instruction). Thus, in this hypothetical example, although the false alarm rates for the two procedures would be equated at .05, the hit rate for the lineup (.60) would exceed that of the showup (.50). A pattern like that illustrates the general finding that lineups support higher discriminability than showups (e.g., Gronlund et al., 2012 ). The common finding that lineups achieve higher discriminability than showups supports the argument that lineups should be preferred to showups whenever possible. Using a showup, it is harder for eyewitnesses to tell the difference between innocent and guilty suspects, so there is never a reason for preferring a showup to a lineup when the police have the option of using either procedure.

In terms of discriminability, why are lineups superior to showups? One theory holds that witnesses do not appreciate that the face of the suspect, innocent or guilty, will necessarily match certain features of the witness’s memory of the perpetrator. For example, if the witness said that the crime was committed by a clean-shaven 20-year-old White male with dark hair and thick eyebrows (indicating that these features are in the witness’s memory), the suspect—innocent or guilty—will likely have those features. Thus, the memory-match signals generated by those features are nondiagnostic of the perpetrator’s identity and only add noise to the decision-making process. It is the remaining facial features (features that were not described but that are represented in the witness’s memory) that are diagnostic. Theoretically, a simultaneous lineup in which each person contains the features described by the witness immediately teaches the witness to disregard those shared (nondiagnostic) features and to focus instead on the other features to determine which of those match memory of the perpetrator. Doing so enhances discriminability ( Wixted & Mickes, 2014 ).

Maximizing Information

A low false alarm rate is generally regarded as being a desirable property of a lineup procedure because it is protective of innocent suspects. And, as just illustrated, for any given low false alarm rate, a lineup can achieve a higher hit rate than a showup can achieve (i.e., lineups yield higher discriminability). However, not everyone agrees that a low false alarm rate is an inherently desirable property of an eyewitness identification procedure. One price that is paid for keeping the false alarm rate low is that many lineup procedures yield no information at all about the suspect in the lineup because the lineup is often rejected (or a filler is identified). This includes lineups containing a guilty suspect. Imagine, for example, a witness who will not identify someone from the lineup unless they are at least 90% sure of being correct. Further imagine that the guilty suspect is in the lineup and that the witness is 85% sure he is the one who committed the crime. Using a standard lineup procedure, the witness will reject the lineup, and the police will never know that the witness could have told them that there is a good chance that their suspect is in fact the perpetrator.

In an ideal world, the lineup procedure would not miss out on useful information like that. For example, instead of using a lineup, the police might want to use a showup procedure after all, perhaps with instructions that encourage a liberal response bias (e.g., Smith et al., 2019 ). Under those conditions, many suspect identifications would occur with some level of confidence, so information about the suspect would be obtained in most cases. Alternatively, instead of using a showup, witnesses could be asked to provide a confidence rating for everyone in the lineup ( Brewer et al., 2020 ). This procedure ensures that information about the degree to which the suspect matches memory of the perpetrator is obtained from every lineup (because the suspect always receives a confidence rating). Still another possibility would be to take a perceptual scaling approach to reveal the structure of the eyewitness’s memory for the faces in a lineup ( Gepshtein et al., 2020 ). This approach is unique in that it takes the decision out of the hands of the witness and puts into the hands of the memory expert after the degree to which the suspect stands out from the fillers in the eyewitness’s memory is measured.

For the foreseeable future, it seems likely that the police will continue to use lineups. So long as they do, maximizing discriminability is a reasonable goal. This means preferring lineups to showups whenever possible. In addition, according to a review of published and unpublished studies, Mickes and Wixted (in press) found that simultaneous lineups (faces shown all at once) reliably yield higher discriminability than sequential lineups (faces shown one at a time). Theoretically, this might reflect the same feature-discounting process that explains why simultaneous lineups are superior to showups; that is, nondiagnostic facial features are more easily and appropriately discounted when the faces are shown simultaneously compared to when they are shown sequentially. Whether or not that is true, because it empirically achieves higher discriminability, it is reasonable for the police to prefer the simultaneous procedure to the sequential procedure. Eventually, however, should the information maximizing approach be empirically shown to yield superior outcomes, it is possible to imagine one of those approaches (e.g., perceptual scaling) ultimately replacing the standard lineup approach.

Test a Witness’s Memory for a Suspect Only Once

There is one additional recommendation for conducting lineups or showups that warrants special consideration. For the first time in any publication expressing a scientific consensus, the explicit recommendation was made to avoid repeated tests of a suspect beyond the first test ( Wells et al., 2020 ). More specifically, Recommendation #8 is termed the “Avoid Repeated Identifications Recommendation” and reads as follows: “Repeating an identification procedure with the same suspect and same eyewitness should be avoided regardless of whether the eyewitness identified the suspect in the initial identification procedure” (p. 8). The justification for this novel recommendation was described as follows:

This recommendation holds no matter how compelling the argument in favor of a second identification might seem (e.g., the original photo of the suspect was not as good as it could have been; the witness was nervous during the first identification test and is calmer now; the initial identification was made from a social media profile, but it would be more desirable to have an identification made using proper police procedures). The importance of focusing on the first identification test cannot be emphasized strongly enough . . . eyewitness identification evidence has a unique characteristic that makes it unsuitable for what might be called “repeated testing.” Whether the eyewitness is asked to make an identification with a showup or a lineup, there is only one uncontaminated opportunity for a given eyewitness to make an identification of a particular suspect. Any subsequent identification test with that same eyewitness and that same suspect is contaminated by the eyewitness’s experience on the initial test . ( Wells et al., 2020 , p. 25, emphasis added)

In other words, testing memory for a suspect changes the witness’s memory for that suspect. Assuming a recognizable photo of the suspect and a good faith attempt on the part of the eyewitness to make an identification, this is unavoidably true ( Wixted et al., 2021 ). If the suspect is innocent, it is the first time the witness is seeing that face. Moreover, seeing that face creates a new memory record of it in face-processing regions of the brain at a time when the witness happens to be thinking about the crime. As a result, the memory record of the innocent suspect’s face will also be associated with the activated memory of the crime. This occurs even if the witness rejects the lineup or picks a filler. Even then, a memory of the suspect has been formed and associated with memories of the crime. It is why no second test can provide more reliable information than the first. Why rely on a second test that is prejudicial to the potentially innocent suspect when only the first test can provide a clean and fair test of the witness’s uncontaminated memory?

The idea that it is essential to test a witness’s memory for a suspect only once is counterintuitive to many. After all, everyone has had the experience of failing to recall a detail (e.g., someone’s name) and then successfully recalling that detail when trying to do so again at some later point, perhaps even days or weeks later. However, this common experience involves recalling information from memory. Unlike face recognition, recall involves a memory search process. A search process can take a long time to succeed on the first test, or it can fail on the first test and then succeed on a later test. As noted earlier, the latter phenomenon is known as reminiscence. A failed memory search on a first test of recall does not contaminate memory because nothing happened to change the witness’s memory.

However, face recognition is not like that. No search of memory is required because the sought-after information (the face) is physically presented to the witness as part of the photo lineup. As noted earlier, if the suspect is guilty, the sensory information generated by that face will activate the same brain region where the memory of the perpetrator’s face was stored when the facial information was originally processed during the crime. It is not a search process that is extended in time and that can fail on the first try and then succeed on a later try. Because it is not a search process, if it succeeds, it will happen within seconds (not minutes). Moreover, if it fails on the first try, it means that the face of the suspect does not match memory.

To reiterate: Assuming good faith on the part of the witness and a recognizable photo of the suspect, if face recognition does not succeed within seconds of seeing the suspect’s face, it means that the suspect’s face does not match the witness’s memory. Period. This can happen because the witness failed to form a memory of the perpetrator’s face, in which case the suspect’s face would not match memory even if the suspect is guilty, or because the witness did form a memory of the perpetrator’s face, but the suspect is innocent. Either way, if the same suspect’s face that failed to match memory on the first test matches memory on a later test, it is a tell-tale sign that the witness’s memory was contaminated, not a sign that the witness “found” a face memory that they searched for and failed to find on the first test. It is not possible to overstate the importance of this point.

Although the first test of an eyewitness’s memory unavoidably contaminates the witness’s memory for the suspect, once again, it is obviously not the only source of memory contamination. In the weeks and months following the first test, if the police maintain their focus on the suspect, the witness might encounter the suspect’s face again multiple times. For example, the suspect’s face might appear on the news or might be seen in pretrial hearings, or the witness might search for his face in other ways (e.g., on social media). When the witness does finally identify the suspect (perhaps after initially rejecting the lineup), the police might also provide feedback to the witness indicating that it was the correct choice, thereby increasing the witness’s confidence beyond what it otherwise would be ( Wells & Bradfield, 1998 ). Meanwhile, if the suspect is innocent, the memory of the actual perpetrator’s face will be steadily fading away (having been seen only once at the time of the crime).

Again, the key point is that if face recognition of the suspect fails on the first test and then seems to succeed on any later test, it is a tell-tale sign of memory contamination, not a sign of a successful search of memory that previously failed. The failure to appreciate that simple fact appears to be the main reason why so many people are under the impression that eyewitness memory is inherently unreliable. In his book Convicting the innocent: Where criminal prosecutions go wrong , Garrett (2011) analyzed trial materials for 161 DNA exonerees who had been misidentified by one or more eyewitnesses in a court of law. In every case, the eyewitness testified with high confidence at trial that the defendant was the perpetrator. Testifying with high confidence at trial is the norm. However, identifications that occur at trial are not initial identifications, which, as known now, are the uniquely informative identifications. Thus, the question of interest is what happened on the first test (conducted early in the police investigation), not the last test (conducted in front of the judge and jury, at trial, long after memory was contaminated). The first test changes memory, so if the witness made a good faith attempt to recognize the perpetrator from a photo lineup containing a recognizable photo of the suspect, the results of no later test can serve the cause of justice better than the results of the first test.

Critically, in 57% of the DNA exoneration cases in which an innocent defendant was known to have been misidentified in court by an eyewitness, there was testimony about the outcome of the initial memory test. As Garrett (2011) put it:

I expected to read that these eyewitnesses were certain at trial that they had identified the right person. They were. I did not expect, however, to read testimony by witnesses at trial indicating that they earlier had trouble identifying the defendants. Even if there had been problems, eyewitnesses might not recall their hesitance at the time they first identified the defendant. Yet in 57% of these trial transcripts (92 of 161 cases), the witnesses reported that they had not been certain at the time of their earlier identifications. (p. 49, emphasis in original)

Thus, it seems that the key mistake in these cases was not made by the eyewitnesses after all. Instead, the key mistake was made by the criminal justice system, which did not keep its focus on the results of the first (and uniquely informative) test. Had the focus been placed on the outcome of the first test, many of the DNA exoneration cases that are ordinarily attributed to the unreliability of eyewitness memory may not have resulted in a conviction. The reason is that eyewitness identification evidence would not have played a significant role at the trial because, on the first test, that evidence was inconclusive at best.

Disregard the Witness’s Explanation for Why a Face Recognition Decision Changed

Unfortunately, Key et al. (2022) recently found that mock jurors tended to vote “guilty” when the eyewitness’s confidence was high, regardless of when the confidence judgment was made (initially or at trial) or whether there were inconsistencies in the confidence levels. This is consistent with the DNA exonerations cases reviewed by Garrett (2011) . Almost always, jurors focus on how certain the eyewitness appears at trial, long after their memory has been contaminated (unbeknownst either to the eyewitness or to the jury). Research into why that is suggests that jurors believe that virtually any excuse provided by the witness justifies removing the focus from the first test and placing it instead on the last test ( Jones et al., 2008 ). As observed by Key et al. (2022) : “Jurors need a more nuanced appreciation of the role of eyewitness confidence, and we discuss ideas for potential interventions that may aid jurors’ decision making.” The focus should be kept on the first test, regardless of how a witness rationalizes why they are confident now even though they were not confident on the first test.

These considerations underscore another point that also cannot be emphasized strongly enough. As noted earlier, face recognition memory does not fail and later succeed, and this remains true no matter how the witness rationalizes the difference between what they said on the first test and what they later say in court . Witnesses at trial are not aware that they are misidentifying an innocent suspect with high confidence because their memory was contaminated. How could they know? What they do know is their current high confidence was not present on the first test, and coming up with a believable explanation of why that is turns out to be surprisingly easy to do. For example, the witness might say “I was nervous on the first,” or “I did not think carefully on the first test and later searched my memory more carefully,” or “I had an epiphany during a dream” ( Jones et al., 2008 ). Unfortunately, the witness’s rationalization of the apparent discrepancy makes sense not only to the witness but also to the judge and jury ( Key et al., 2022 ).

In light of these considerations, it seems fair to say that the controllable mistake made in many of the wrongful convictions later overturned by DNA evidence was not a mistake made by the eyewitnesses; instead, the controllable mistake was the failure of triers of fact to focus on the results of the first test only.

Under the Right Conditions, Eyewitness Memory Is Highly Reliable

Testing a witness’s memory early in a police investigation (thereby minimizing the chances that memory has been contaminated) using a proper interview or a proper photo lineup yields a benefit that was only recently fully appreciated. The benefit is that under those conditions, eyewitness memory is highly reliable, not unreliable. It is reliable in the sense that what is recalled or recognized with high confidence tends to be highly accurate. Yet, even under these ideal conditions, what is recalled or recognized with low confidence is unreliable. A witness who expresses low confidence is essentially saying “there is a good chance I am wrong,” and the evidence shows that they are right about that. If only the police would listen to them and stop right there (never testing the witness’s memory for the same suspect again), it is possible that no one would have ever come to believe that eyewitness memory is inherently unreliable.

To say that eyewitness memory is reliable on the first, properly conducted test is to say that the relationship between confidence and accuracy is strong (i.e., low confidence implies low accuracy, whereas high confidence implies high accuracy). Consider, for example, studies testing recall using open-ended, nonleading questions, which were recently reviewed by Wixted and Mickes (2022) . In a study by Roberts and Higham (2002) , participants watched a videotape of a simulated robbery and were interviewed a week later about their recollections of the event. Confidence for each recalled detail was collected using a 1 to 7 scale. As shown in figure 1 , confidence was strongly related to accuracy.

Figure 1. Accuracy (percent correct) as a function of confidence for the interview recall data reported by Roberts and Higham (2002) . The overall number of correct details (considered relevant to an investigation) and incorrect details was estimated for each level of confidence from their Figure 1 and then the probability that a recalled detail was correct was computed for each level of confidence. Error bars represent standard error.

In a later study by Odinot et al. (2013) , participants watched a television show about an accident between a car and a motorcycle. One, three, or five weeks later, they completed a questionnaire consisting of 28 open-ended questions, and they rated their confidence in each recalled detail using a 7-point scale. The results showed not only that confidence was strongly indicative of accuracy, but high confidence implied high accuracy in all three conditions (figure 2 ).

Figure 2. Accuracy (percent correct) as a function of confidence estimated from the interview recall data when recall took place 1, 3, or 5 weeks after encoding reported in Figure 1 of Odinot et al. (2013) .

In related work, Spearing and Wade (2021) asked participants to recall details from a mock-crime video they had previously viewed. The participants rated confidence immediately following each freely recalled detail (Immediate) or after all information had first been recalled (Delayed). As usual, the relationship between confidence and accuracy was strong, and this was true of both conditions (figure 3 ).

Figure 3. Accuracy (percent correct) as a function of confidence for the interview recall data reported by Spearing and Wade (2021) . The data were estimated from their Figure 4 (Experiment 3). Experiment 3 was deemed by the authors to be the most forensically relevant of the three experiments they reported because it involved a free recall narrative report. The diagonal line represents a perfect confidence–accuracy relationship.

The studies discussed were laboratory studies. In a study of actual eyewitnesses to a crime, Odinot et al. (2009) interviewed witnesses of an armed robbery that was recorded by multiple security cameras, and the recordings were used to verify the recalled information. The witnesses were interviewed 3 months after the crime, which is not ideal because considerable memory contamination can occur over that period (e.g., from conversations between witnesses or TV coverage). Yet figure 4 shows that proportion correct increased from .61 to .85 as confidence increased from low to high. These numbers might be even more impressive had the interviews been conducted immediately after the crime, minimizing the opportunity for memory contamination.

Figure 4. Observed relationship between percentage of recalled details that were correct and confidence. The data are from Odinot et al. (2009) . Error bars represent standard error.

The same story applies to eyewitness memory initially tested by recognition using a proper lineup procedure ( Wells et al., 2020 ). The attempt to measure that relationship has a long and complicated history, but the short story is that prior efforts using a correlation or calibration approach were misleading. The question of primary interest to triers of fact is the relationship between confidence and accuracy for suspect identifications (leaving out witnesses who identify a filler or reject the lineup). Plotting a confidence–accuracy relationship for suspect identifications is known as a confidence–accuracy characteristic (CAC) plot ( Mickes, 2015 ).

Wixted and Wells (2017) reviewed the literature, replotting all the previously collected correlation and calibration data in terms of CAC. As shown in figure 5 , confidence is strongly predictive of accuracy, with high-confidence suspect identification being very accurate.

Figure 5. Suspect identification accuracy (percent correct) as a function of confidence averaged across 15 studies with comparable scaling on the confidence (x) axis ( Wixted & Wells, 2017 ). Error bars represent standard error.

According to a recent study of actual eyewitnesses making identifications from properly administered fair lineups ( Wixted, Mickes, et al., 2016 ), these results generalize to the real world (figure 6 ).

Figure 6. Estimated suspect identification accuracy (percent correct) as a function of confidence for the data from the Houston Police Department field study ( Wixted, Mickes, et al., 2016 ). The crimes were robberies, the lineups were fair, the lineups were administered by an officer who was blind to the identity of the suspect, and the suspects in the lineups were not previously known to the witnesses.

Interestingly, for tests of eyewitness identification, the confidence–accuracy relationship remains strong whether the retention interval (the time between the witnessed crime and the first eyewitness identification test) is short or long. As noted earlier, when memory is tested by recall, the longer the retention interval, the more opportunity there is for memory to be contaminated (e.g., from conversations with other witnesses, hearing rumors). Although the same principle applies to a test of eyewitness identification, memory is much less likely to be contaminated by the mere passage of time. The reason is that, with regard to eyewitness identification, what contaminates the witness’s memory is encountering the face of the suspect who will later appear in a lineup. Conversations with other witnesses or hearing rumors about the crime usually have no contaminating effect on eyewitness identification because the face of the innocent suspect is not encountered (so a memory of the face is not created in the face processing regions of the brain). Moreover, no matter how long the retention interval is, it is unlikely that the witness will encounter the face of the same innocent suspect who the police will later come to suspect and place in a lineup. In agreement with this way of thinking, the length of the retention interval has little effect on the confidence–accuracy relationship for retention intervals as long as 9 months ( Wixted, Read, et al., 2016 ).

The take-home message seems almost inescapable: Always focus on the first good faith, properly conducted test of an eyewitness’s memory, and never ignore the level of confidence expressed by the witness on that test. Low confidence implies low accuracy, and by expressing low confidence, the witness is making it clear to police investigators that what is being reported from memory stands a good chance of being wrong. But if confidence is high, and if the test was properly conducted, what is remembered by an honest eyewitness on the first test is likely to be highly reliable. Such words have rarely been used to describe eyewitness memory, but the data (some of which was summarized here) are consistent with this more nuanced understanding. As it turns out, as with other types of forensic evidence, eyewitness memory is reliable under some conditions and unreliable under other conditions. The job of judges and jurors is to determine, for any given case, which set of conditions applies. Doing so serves the cause of justice by imperiling the guilty and protecting the innocent.

Eyewitness Memory Is a Lot More Reliable Than You Think

What law enforcement—and the public—needs to know

By John Wixted & Laura Mickes

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The ability of a person who witnesses a crime to later pick the perpetrator out of a lineup is atrocious—right? The answer seems like a resounding “yes” if you consider some well-known and rather disconcerting information. Eyewitness misidentifications are known to have played a role in 70 percent of the 349 wrongful convictions that have been overturned based on DNA evidence (so far). Psychologists have learned a lot about why such errors happen. With surprising ease, for example, participants in a memory experiment can be led to believe that they saw a stop sign when they actually saw a yield sign or that they became lost in a shopping mall as a child when no such experience actually occurred. In much the same way, an eyewitness can be led to falsely remember someone committing a crime that was actually committed by someone else.

But there is more to the story. Consider the important, and often overlooked, distinction between malleability and reliability. Just because memory is malleable—for example, it can be contaminated with the trace of an innocent person—does not mean that it has to be unreliable. What it means is that the malleability of memory can harm reliability. Once this fact is appreciated, then proper testing protocols can be put in place to minimize the likelihood that the original memory trace is contaminated.

Current procedures for collecting and assessing evidence from eyewitnesses are often not designed to minimize contamination.This problem does not apply to other kinds of forensic evidence. Imagine if police let unauthorized people have willy-nilly access to a crime scene that is under investigation. What would that mean for the reliability of the blood or fingerprint evidence, for example, collected at that scene? Blood and fingerprint evidence, per se, would not be deemed unreliable. Instead evidence collected at the contaminated crime scene would probably be declared inadmissible. Not so with eyewitness memory.

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Any evidence can potentially be contaminated, including what is considered to be the gold standard of forensic evidence: DNA. Like eyewitness memory, DNA evidence can be contaminated with the trace of an innocent person. If the contaminated evidence is relied on to establish guilt versus innocence at a trial, the risk of a wrongful conviction is high. Consider, for example, the case of Gary Leiterman, who, in 2005, was convicted of murder and sentenced to life in prison following a cold case investigation in which his DNA was found on the clothing of a woman named Jane Mixer, who was murdered in 1969. Many believe that this conviction was based on contaminated DNA evidence .

What facts gave rise to the belief that Leiterman may have been wrongfully convicted based on contaminated evidence? First, another DNA profile—one belonging to John Ruelas, who was just a four-year-old preschooler at the time of the murder—was found on a blood spot taken from the victim’s left hand. Even though no connection between Leiterman and Ruelas was ever established, the prosecution theorized that all three must have been together after midnight at the murder scene in 1969, with the preschooler bleeding on the victim for some unknown reason while Leiterman killed her. According to the same theory, 33 years later, in 2002, in an almost inconceivable coincidence, evidence samples from Mixer, Ruelas and Leiterman just happened to be together again in the Michigan State Police Laboratory. The murder victim’s cold case evidence was there because the case had recently been reopened; the 1969 preschooler’s DNA sample was there as part of an active murder investigation, and Leiterman’s DNA sample was there because he had recently been arrested for forging a prescription. The nearly simultaneous analyses of evidence from these three cases in the same crime lab in 2002—a reunion, of sorts, among Mixer, Ruelas and Leiterman, who were ostensibly last together on the night of the murder in 1969—was either an incredible coincidence or the Mixer evidence was contaminated with DNA from both Leiterman and Ruelas.

Instead of concluding that DNA evidence is inherently unreliable because of the contamination that apparently occurred in this case, a more reasonable conclusion would be that for DNA testing to be reliable, proper protocols must be followed. Few would doubt that under such conditions, DNA evidence is highly reliable. The same is true of eyewitness memory: memory can be contaminated with the trace of an innocent person, but under proper testing conditions, eyewitness evidence is highly reliable. As with DNA evidence, eyewitness evidence needs to be safeguarded against contamination.

To do this, proper testing protocols that reduce chances of contamination need to be followed. Some elements include the following: First, and most important of all, because the test itself contaminates memory, only the initial memory test provides uncontaminated results. Subsequent memory tests, including the dramatic one that occurs in court in front of the jury, constitute contaminated evidence. Second, the police lineup has to be fair (that is, the suspect should not stand out). And third, the confidence expressed by the eyewitness following an identification of someone from the lineup must be recorded. Assessing confidence is critical because it provides direct information about the trustworthiness of the uncontaminated ID. An initial eyewitness identification made with low confidence indicates that even though memory was not contaminated, the ID is untrustworthy (that is, by indicating low confidence, the eyewitness is effectively saying, “There’s a good chance that I’m making an error”). In contrast, a high-confidence ID is highly accurate , a surprising fact that has only recently come to be appreciated by experimental psychologists. In a recent review of the literature, the authors reported across 15 experiments, suspect identifications made with high confidence were, on average, 97 percent accurate!

Although the high accuracy of an initial ID made with high confidence is important to appreciate, the low accuracy of an ID made with low confidence may be even more important to appreciate. To see why, let us revisit those DNA exoneration cases that so often involve eyewitness misidentification. University of Virginia law professor Brandon Garrett analyzed trial materials for 161 DNA exonerated individuals who had been misidentified with high confidence by one or more eyewitnesses in a court of law. By itself, that fact only shows that contaminated memory is unreliable (just as contaminated DNA evidence is). But in 57 percent of those cases, it was possible to determine what happened on the initial (uncontaminated) memory test. For every one of those tests, the eyewitnesses were, at best, uncertain .

Attributing that error to the unreliability of eyewitness memory is, in our view, pointing the finger of blame in the wrong direction. Eyewitness memory is reliable when initially tested using proper procedures, but the legal system nonetheless habitually relies on unreliable (contaminated) eyewitness evidence from later IDs. The sooner police, prosecutors and judges understand that fact, the better off we all will be—including you, if you are ever incorrectly fingered by an eyewitness.

John Wixted is a Distinguished Professor of Psychology at the University of California, San Diego.

Laura Mickes is an academic at Royal Holloway, University of London.

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The effects of stress on eyewitness memory: A survey of memory experts and laypeople

1 Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, Maastricht, The Netherlands 6229 ER

2 Department of Psychology, University of Portsmouth, Portsmouth, UK

Henry Otgaar

3 Faculty of Law, Catholic University of Leuven, Leuven, Belgium

Melanie Sauerland

Conny w. e. m. quaedflieg, lorraine hope, associated data.

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.

Supplementary Information

The online version contains supplementary material available at 10.3758/s13421-020-01115-4.

Witnesses often experience acute stress in forensic contexts, whether during a crime or during subsequent police interviews (Bornstein, Hullman, & Miller, 2013 ; J. A. Davis, 2016 ; Yuille & Cutshall, 1986 ). Facing difficult, frightening, and emotional events can trigger a subjective and physiological stress response from the witness (Bornstein & Robicheaux, 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 preexisting ‘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 noncomplex stimuli, such as word lists or numeric strings). Generally, across fields, research shows that acute stress at retrieval impairs memory (e.g., Schwabe, Joëls, Roozendaal, Wolf, & Oitzl, 2012 ; Shields, Sazma, McCullough, & Yonelinas, 2017 ; Wolf, 2017 ), although limited research on this specific issue has been 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, Bornstein, Penrod, & McGorty, 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, O’Toole, Easterly, & Loftus, 2006 ; Yarmey & Jones, 1983 ). For example, Schmechel et al. ( 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, Brezler, McNamara, Malette, & Vuorre, 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 with 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 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, Hermans, Pu, Joëls, & Fernández, 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, Fernández, & Roozendaal, 2011 ; Robbins, 1984 ; Ulrich-Lai & Herman, 2009 ). The rapid catecholaminergic and nongenomic glucocorticoid actions set the brain in a memory formation mode (Diamond, Campbell, Park, Halonen, & Zoladz, 2007 ; Joëls, Pu, Wiegert, Oitzl, & Krugers, 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, 2020 ; Shields et al., 2017 ; 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 ). Past surveys have examined some general beliefs about stress and memory among both lay and expert samples. Table Table1 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, Ellsworth, & Smith, 1989 ; Kassin, Tubb, Hosch, & Memon, 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 2 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.

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

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

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 more accurately than memories for everyday events (Conway, Justice, & Morrison, 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, Kalin, Thurow, Rosenkranz, & Davidson, 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 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, O’Bryant, & Zickafoose, 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 Table2. 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.

Survey statements about stress and memory with percentage of participant endorsement

Statement	Percentage of participant endorsement
		Eyewitness memory experts = 37	Fundamental memory experts = 36	Laypeople = 109
1. Very high levels of stress impair the accuracy of eyewitness testimony.	Agree	(87.3, 100.0)	(67.7, 93.5)	(89.0, 98.2)
	Disagree	(0.0, 7.9)	(4.5, 28.9)	(0.2, 7.2)
	Don’t know	(0.0, 7.9)	(0.0, 8.2)	(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.	Agree	(68.5, 93.7)	(60.9, 89.1)	(74.4, 89.0)
	Disagree	(0.0, 16.9)	(2.6, 25.2)	(6.5, 19.1)
	Don’t know	(0.8, 20.8)	(0.8, 21.4)	(1.2, 9.8)
3. Experiencing stress while trying to remember something (i.e., at retrieval) impairs memory retrieval.	Agree	(75.5, 97.5)	(82.7, 100.0)	(70.2, 85.8)
	Disagree	(0.0, 7.9)	(0.0, 17.3)	(6.5, 19.1)
	Don’t know	(0.8, 20.8)		(3.8, 14.6)
4. Experiencing stress during an event (i.e., at encoding) enhances memory for that event.	Agree	(17.3, 47.5)	(64.2, 91.4)	(25.0, 42.8)
	Disagree	(46.6, 77.8)	(6.5, 32.2)	(43.8, 62.6)
	Don’t know	(0.0, 12.7)	(0.0, 8.2)	(6.5, 19.1)
5. Children’s memories are less affected by stress experienced during an event (i.e., at encoding) than adults’ memories.	Agree	(0.0, 12.7)	(0.0, 8.2)	(19.1, 35.9)
	Disagree	(58.7, 87.3)	(39.4, 71.8)	(47.6, 66.2)
	Don’t know	(8.3, 34.9)	(25.6, 57.8)	(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.	Agree	(65.1, 91.7)	(67.7, 93.5)	(35.7, 54.3)
	Disagree	(0.8, 20.8)	(4.5, 28.9)	(26.8, 44.8)
	Don’t know	(0.8, 20.8)	(0.0, 8.2)	(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.	Agree	(40.8, 72.8)	(57.6, 86.8)	(67.1, 83.3)
	Disagree	(6.3, 31.5)	(0.0, 17.3)	(4.4, 15.8)
	Don’t know	(10.5, 38.1)	(6.5, 32.3)	(8.1, 21.3)
8. Stress affects memory for faces differently than memory for other types of stimuli.	Agree	(22.2, 53.4)	(6.5, 32.3)	(55.2, 73.2)
	Disagree	(17.3, 47.5)	(23.0, 54.8)	(5.8, 18.0)
	Don’t know	(15.0, 44.4)	(25.6, 57.8)	(15.9, 31.9)
9. The memory of trained professionals, such a police officers, will be less affected by stress than the memory of normal eyewitnesses.	Agree	(2.5, 24.5)	(6.5, 32.3)	(55.2, 73.2)
	Disagree	(75.5, 97.5)	(57.6, 86.8)	(20.8, 38.0)
	Don’t know		(0.0, 17.3)	(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.	Agree	(61.9, 89.5)	(42.2, 74.4)	(71.2, 86.6)
	Disagree	(6.3, 31.5)	(6.5, 32.3)	(6.5, 19.1)
	Don’t know	(0.0, 12.7)	(8.6, 35.8)	(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.	Agree	(4.3, 28.1)	(2.6, 25.2)	(78.7, 91.9)
	Disagree	(61.9, 89.5)	(54.3, 84.5)	(2.4, 12.2)
	Don’t know	(0.0, 16.9)	(4.5, 28.9)	(2.4, 12.2)
12. Eyewitnesses have more difficulty remembering violent events than nonviolent ones.	Agree	(24.7, 56.3)	(2.6, 25.2)	(34.7, 53.3)
	Disagree	(38.0, 70.2)	(39.4, 71.8)	(27.7, 45.7)
	Don’t know	(0.0, 12.7)	(15.5, 45.7)	(11.9, 26.7)
13. Stressful experiences that are emotional are generally better remembered than stressful experiences that are not emotional.	Agree	(46.6, 77.8)	(45.2, 77.0)	(42.9, 61.7)
	Disagree	(6.3, 31.5)	(8.6, 35.8)	(20.8, 38.0)
	Don’t know	(6.3, 31.5)	(4.5, 28.9)	(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.	Agree	(46.6, 77.8)	54.3, 84.5)	(26.8, 44.8)
	Disagree	(6.3, 31.5)	(4.5, 28.9)	(41.1, 59.9)
	Don’t know	(6.3, 31.5)	(2.6, 25.2)	(7.3, 20.3)
15. Severe levels of stress, but not moderate levels of stress, generally harm eyewitness memory.	Agree	(71.9, 95.7)	(48.2, 79.6)	(54.3, 72.3)
	Disagree	(4.3, 28.1)	(8.6, 35.8)	(15.9, 31.9)
	Don’t know		(2.6, 25.2)	(6.5, 19.1)
16. When an eyewitness experiences a relatively short crime (i.e., fewer than 5 minutes), his or her memories are not affected by this stress.	Agree	(0.0, 7.9)		18.3, 34.9)
	Disagree	(83.1, 100.0)	(82.7, 100.0)	(44.7, 63.5)
	Don’t know	(0.0, 12.7)	(0.0, 17.3)	(11.9, 26.7)
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.	Agree	(22.2, 53.4)	(25.6, 57.8)	(48.5, 67.1)
	Disagree	(19.7, 50.5)	(36.5, 69.1)	(16.7, 32.9)
	Don’t know	(12.7, 41.3)	(0.0, 13.1)	(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.	Agree	(15.0, 44.4)	(8.6, 35.8)	(37.4, 56.2)
	Disagree	(22.2, 53.4)	(25.6, 57.8)	(22.5, 39.9)
	Don’t know	(17.3, 47.5)	(20.4, 51.8)	(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.	Agree	(46.6, 77.8)	(15.5, 45.7)	(48.5, 67.1)
	Disagree	(4.3, 28.1)	(28.2, 60.6)	(15.9, 31.9)
	Don’t know	(8.3, 34.9)	(10.9, 39.1)	(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.	Agree	(0.8, 20.8)	(6.5, 32.3)	(36.5, 55.3)
	Disagree	(27.2, 59.2)	(54.3, 84.5)	(21.7, 38.9)
	Don’t know	(29.8, 62.0)	(0.8, 21.4)	(15.9, 31.9)
21. Memories of older adults (ages 55+) are less affected by stress experienced during an event (i.e., at encoding) than memories of younger adults (ages 18–35).	Agree	(0.0, 12.7)	(0.0, 17.3)	(14.2, 29.8)
	Disagree	(27.2, 59.2)	(30.9, 63.5)	(49.5, 67.9)
	Don’t know	(35.3, 67.5)	(28.2, 60.6)	(11.9, 26.7)
22. Effects of stress on memory are driven primarily by autonomic nervous system activity.*	Agree	(22.2, 53.4)	(13.2, 42.4)
	Disagree	(2.5, 24.5)	(42.2, 74.4)
	Don’t know	(32.5, 64.7)	(2.6, 25.2)
23. Encoding is facilitated when the autonomic nervous system is activated while experiencing an emotional event such as a crime.*	Agree	(32.5, 64.7)	(86.9, 100.0)
	Disagree	(2.5, 24.5)	(0.0, 8.2)
	Don’t know	(22.2, 53.4)	(0.0, 8.2)
24. Rapid nongenomic glucocorticoids have a beneficial effect on memory formation for an event such as a crime.*	Agree	(2.5, 24.5)	(36.5, 69.1)
	Disagree	(0.0, 7.9)	(0.8, 21.4)
	Don’t know	(71.9, 95.7)	(20.4, 51.8)
25. Slow genomic glucocorticoids have a detrimental effect on memory formation for an event such as a crime.*	Agree	(2.5, 24.5)	(13.2, 42.4)
	Disagree	(0.0, 7.9)	(15.5, 45.7)
	Don’t know	(71.9, 95.7)	(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.*	Agree	(8.3, 34.9)	(25.6, 57.8)
	Disagree	(0.8, 20.8)	(6.5, 32.3)
	Don’t know	(58.7, 87.3)	(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.*	Agree	(4.3, 28.1)	(15.5, 45.7)
	Disagree	(0.8, 20.8)	(20.4, 51.8)
	Don’t know	(58.7, 87.3)	(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.*	Agree	(4.3, 28.1)	(13.2, 42.4)
	Disagree	(0.0, 16.9)	(20.4, 51.8)
	Don’t know	(61.9, 89.5)	(20.4, 51.8)
29. When noradrenergic arousal interacts with nongenomic glucocorticoids during retrieval, memory is typically impaired.*	Agree	(2.5, 24.5)	(28.2, 60.6)
	Disagree		(0.8, 21.4)
	Don’t know	(75.5, 97.5)	(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)

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 preregistered on the OSF ( https://osf.io/b93px?view_only=f83715544c4640c79c3fbfa50d996154 ). Table Table3 3 presents the demographic information for both the final laypeople and expert samples.

Overview of survey participants’ demographics

	Age	Gender	Race/ethnicity*	Nationality	Education	Legal system involvement
Laypeople = 109	= 37.52 = 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 orsome college)	Been on a jury: 15.6% Witnessed a crime: 34.9% ( = 21 for violent crime, = 17 for nonviolent crime) Of these, 34.2% ( = 13) directlyinvolved in criminal justice system
Experts = 73	= 46.07 = 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

Age

Gender

Race/ethnicity*

Nationality

Education

Legal system involvement

Laypeople

= 109

= 37.52

= 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 orsome college)

Been on a jury:

15.6%

Witnessed a crime:

34.9%

( = 21 for violent crime,

= 17 for nonviolent crime)

Of these, 34.2% ( = 13) directlyinvolved in criminal justice system

Experts

= 73

= 46.07

= 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

Note. * = multiple choices possible. ** = one response missing

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

We recruited 129 American participants using Amazon Mechanical Turk (MTurk), an online crowdsourcing marketplace. MTurk has been shown to be a viable platform for academic data collection when compared with other commonly used platforms (Kees, Berry, Burton, & Sheehan, 2017 ). We selected this platform because of 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.

Following earlier surveys (Kassin et al., 1989 ; Kassin et al., 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 ) 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 4-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 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 more than 6 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 postsurvey.

These self-reported experts received additional demographic questions about their research (see Table Table3). 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, two-way mixed-effects model) = .866, 95% CI [.709. .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 were fundamental memory experts. Experts were thanked upon completion, but received no reimbursement.

We created the survey using the online platform Qualtrics (Qualtrics, Provo, UT), with separate versions for laypeople and experts. Both survey versions and data sets 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 Table2 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 ; Kassin et al., 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, 2020 ; Shields et al., 2017 ). 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 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, Melinder, Stridbeck, & Raja, 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, Ross, Bradshaw, Thomas, & Bradshaw, 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) whether they believed the statement was reliable enough for psychologists to present in courtroom testimony (yes or no; court reliability ); (b) whether their opinion was based on published, peer reviewed, and scientific research (yes or no; research basis ); and (c) whether they would say that most laypeople believe the statement to be true as 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.

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, χ 2 (1, N = 133) = 0.011, p = .917, φ = .009.

Eyewitness experts versus fundamental memory experts

Table Table2 2 presents expert responses and for each statement, categorized by research field. Figure Figure1 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 Table4 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.

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Survey statements about stress and memory with percentage of participant endorsement and 95% confidence intervals

Inferential statistics for 2 × 2 χ 2 tests comparing endorsements ( agree versus disagree ) in eyewitness and fundamental memory experts ( df = 1)

Statement		χ		Adjusted	φ
1. High stress impairs*	71		.055	.084	.241
2. Police interview*	65		.475	.084	.099
3. Stress impairs retrieval*	69		.615	.084	.113

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*	38		>.999	.084	.057
22. Primarily ANS activity	50	8.099	.004	.084	.402
23. ANS facilitates*	58		.032	.084	.303
24. Rapid cortisol is beneficial*	29		>.999	.084	.008
25. Slow cortisol is detrimental*	27		.182	.084	.299
26. Noradrenergic alone*	33		>.999	.084	.047
27. Glucocorticoid alone	34	0.567	.452	.084	.129
28. HPA & ANS activated*	32		.433	.084	.209
29. HPA & ANS retrieval*	25		.549	.084	.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)

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 three 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% 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 with agree or disagree ; see Table D in the 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 Table2 2 presents layperson responses for each statement. Table Table5 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 with 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 with laypeople.

Inferential Statistics for 2 × 2 χ 2 tests comparing endorsements ( agree versus disagree ) in experts and laypeople ( df = 1)

Statement		χ		Adjusted	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


7. Test type	150	0.959	.327	.078	.080


10. Victims more affected	163	1.837	.175	.078	.106

12. Violent events	148	6.463	.011	.078	.209
13. Emotional better remembered	149	1.992	.158	.078	.116

15. Severe stress	163	0.984	.321	.078	.078

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

21. Older adults less affected	126	2.984	.084	.078	.154

For these statistically significant statements, we also descriptively examined responses on a broader scale (see Table A in supplementary materials) 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 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 the 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, χ 2 (1, N = 182) = 16.88, p < .001, φ = .305.

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 (see Table Table2). 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 ; Kassin et al., 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.

Prior research examining the effects of stress during encoding on memory is mixed, with different results often emerging across research fields (e.g., S. D. Davis, Peterson, Wissman, & Slater, 2019 ; Deffenbacher et al., 2004 , vs. Henckens et al., 2009 ; Hoscheidt, LaBar, Ryan, Jacobs, & Nadel, 2014 ; 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, Pirke, & Hellhammer, 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, Bohringer, Chatterjee, & Schachinger, 2008 ; Smeets, Giesbrecht, Jelicic, & Merckelbach, 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., Bailis & Mueller, 1981 ; Brigham, Maass, Martinez, & Wittenberger, 1983 ; Clifford & Hollin, 1981 ; Kramer, Buckhout, & Eugenio, 1990 ). Additionally, many eyewitness experiments rely only on self-reported stress as a manipulation check for the stress induction (e.g., Buckhout, Alper, Chern, Silverberg, & Slomovits, 1974 ; S. D. 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 & 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

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, Pulopulos, & Salvador, 2019 ; Smith, Dijkstra, Gordon, Romero, & Thomas, 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., Hope et al., 2016 ; Hosch & Bothwell, 1990 ; Kassin, 1984 ), 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 medium levels of stress (e.g., Abercrombie, Kalin, Thurow, Rosenkranz, & Davidson, 2003 ; de Kloet, Oitzl, & Joëls, 1999 ; Lupien, Maheu, Tu, Ficco, & Schramek, 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 underresearched 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 nonemotional ones ( emotional better remembered ), an account supported by research (Cahill, Gorski, & Le, 2003 ; Kuhlmann, Piel, & Wolf, 2005 ; Shields et al., 2017 ; but see Schwabe et al., 2008 ; Shermohammed, Davidow, Somerville, & Murty, 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, van der Kooy, & Merckelbach, 2000 ). Eyewitness memory experts likely related this statement to the weapon focus effect (e.g., Kramer et al., 1990 ; Loftus, Loftus, & Messo, 1987 ), a phenomenon demonstrating that eyewitness memory for faces and other details is poorer if a weapon was present during a crime (Fawcett, Fawcett, Peace, & Christie, 2013 ). Finally, the majority of both groups disagreed that those who experience stress are more likely to have repressed 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., 2003 ; de Quervain, Roozendaal, Nitsch, McGaugh, & Hock, 2000 ; 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 is sometimes even enhanced ( immediate retrieval enhances ; Schönfeld, Ackermann, & Schwabe, 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 2 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., 2011 ; Joëls et al., 2006 ; Quaedflieg & Schwabe, 2018 ; Roozendaal, 2002 ; Schwabe et al., 2012 ) that delineate the specific timing and roles the autonomic nervous 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 generally showed 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 nongenomic 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.

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 with 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 with 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 underresearched 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 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, 1992 , 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, Sanchez, & Sego, 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 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 preexisting 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

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 ) 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 ). 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 versus peripheral details or free recall versus 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 ; Kassin et al., 2001 ). Nonetheless, analyses comparing expert groups might be underpowered due to the limited 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 I 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, nonstatistically 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 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.

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.

(DOCX 55 kb)

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).

Funding information

This research was supported by a fellowship awarded from the Erasmus Mundus Joint Doctorate Program The House of Legal Psychology (EMJD-LP) with Framework Partnership Agreement (FPA) 2013-0036 and Specific Grant Agreement (SGA) 532473-EM-5-2017-1-NL-ERA MUNDUS-EPJD to Carey Marr.

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 1 or several days.

2 We did not originally include the Stress-NL Consortium in our preregistered plan for survey dissemination, but decided to distribute the survey to this organization due to its contact with current stress experts.

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.

Open practices statement

This survey study was preregistered. The preregistration is available ( https://osf.io/b93px?view_only=f83715544c4640c79c3fbfa50d996154 ). The data and materials for the study are available ( https://osf.io/jpra2/?view_only=a87bc3abda8c4cb699299ecfc9cc94d2 ).

Publisher’s note

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Eyewitness Testimony and Memory Construction

Learning objectives.

Describe the unreliability of eyewitness testimony
Explain the misinformation effect

Memory Construction and Reconstruction

Suggestibility.

When someone witnesses a crime, that person’s memory of the details of the crime is very important in catching the suspect. Because memory is so fragile, witnesses can be easily (and often accidentally) misled due to the problem of suggestibility. Suggestibility describes the effects of misinformation from external sources that leads to the creation of false memories. In the fall of 2002, a sniper in the DC area shot people at a gas station, leaving Home Depot, and walking down the street. These attacks went on in a variety of places for over three weeks and resulted in the deaths of ten people. During this time, as you can imagine, people were terrified to leave their homes, go shopping, or even walk through their neighborhoods. Police officers and the FBI worked frantically to solve the crimes, and a tip hotline was set up. Law enforcement received over 140,000 tips, which resulted in approximately 35,000 possible suspects (Newseum, n.d.).

Most of the tips were dead ends, until a white van was spotted at the site of one of the shootings. The police chief went on national television with a picture of the white van. After the news conference, several other eyewitnesses called to say that they too had seen a white van fleeing from the scene of the shooting. At the time, there were more than 70,000 white vans in the area. Police officers, as well as the general public, focused almost exclusively on white vans because they believed the eyewitnesses. Other tips were ignored. When the suspects were finally caught, they were driving a blue sedan.

As illustrated by this example, we are vulnerable to the power of suggestion, simply based on something we see on the news. Or we can claim to remember something that in fact is only a suggestion someone made. It is the suggestion that is the cause of the false memory.

Eyewitness Misidentification

Even though memory and the process of reconstruction can be fragile, police officers, prosecutors, and the courts often rely on eyewitness identification and testimony in the prosecution of criminals. However, faulty eyewitness identification and testimony can lead to wrongful convictions (Figure 1).

A bar graph is titled “Leading cause of wrongful conviction in DNA exoneration cases (source: Innocence Project).” The x-axis is labeled “leading cause,” and the y-axis is labeled “percentage of wrongful convictions (first 239 DNA exonerations).” Four bars show data: “eyewitness misidentification” is the leading cause in about 75% of cases, “forensic science” in about 49% of cases, “false confession” in about 23% of cases, and “informant” in about 18% of cases.

Figure 1 . In studying cases where DNA evidence has exonerated people from crimes, the Innocence Project discovered that eyewitness misidentification is the leading cause of wrongful convictions (Benjamin N. Cardozo School of Law, Yeshiva University, 2009).

How does this happen? In 1984, Jennifer Thompson, then a 22-year-old college student in North Carolina, was brutally raped at knifepoint. As she was being raped, she tried to memorize every detail of her rapist’s face and physical characteristics, vowing that if she survived, she would help get him convicted. After the police were contacted, a composite sketch was made of the suspect, and Jennifer was shown six photos. She chose two, one of which was of Ronald Cotton. After looking at the photos for 4–5 minutes, she said, “Yeah. This is the one,” and then she added, “I think this is the guy.” When questioned about this by the detective who asked, “You’re sure? Positive?” She said that it was him. Then she asked the detective if she did OK, and he reinforced her choice by telling her she did great. These kinds of unintended cues and suggestions by police officers can lead witnesses to identify the wrong suspect. The district attorney was concerned about her lack of certainty the first time, so she viewed a lineup of seven men. She said she was trying to decide between numbers 4 and 5, finally deciding that Cotton, number 5, “Looks most like him.” He was 22 years old.

By the time the trial began, Jennifer Thompson had absolutely no doubt that she was raped by Ronald Cotton. She testified at the court hearing, and her testimony was compelling enough that it helped convict him. How did she go from, “I think it’s the guy” and it “Looks most like him,” to such certainty? Gary Wells and Deah Quinlivan (2009) assert it’s suggestive police identification procedures, such as stacking lineups to make the defendant stand out, telling the witness which person to identify, and confirming witnesses choices by telling them “Good choice,” or “You picked the guy.”

After Cotton was convicted of the rape, he was sent to prison for life plus 50 years. After 4 years in prison, he was able to get a new trial. Jennifer Thompson once again testified against him. This time Ronald Cotton was given two life sentences. After serving 11 years in prison, DNA evidence finally demonstrated that Ronald Cotton did not commit the rape, was innocent, and had served over a decade in prison for a crime he did not commit.

Link to Learning

To learn more about Ronald Cotton and the fallibility of memory, watch these excellent Part 1 and Part 2 videos by 60 Minutes .

Ronald Cotton’s story, unfortunately, is not unique. There are also people who were convicted and placed on death row, who were later exonerated. The Innocence Project is a non-profit group that works to exonerate falsely convicted people, including those convicted by eyewitness testimony. To learn more, you can visit innocenceproject.org .

Dig Deeper: Preserving Eyewitness Memory: The Elizabeth Smart Case

Contrast the Cotton case with what happened in the Elizabeth Smart case. When Elizabeth was 14 years old and fast asleep in her bed at home, she was abducted at knifepoint. Her nine-year-old sister, Mary Katherine, was sleeping in the same bed and watched, terrified, as her beloved older sister was abducted. Mary Katherine was the sole eyewitness to this crime and was very fearful. In the coming weeks, the Salt Lake City police and the FBI proceeded with caution with Mary Katherine. They did not want to implant any false memories or mislead her in any way. They did not show her police line-ups or push her to do a composite sketch of the abductor. They knew if they corrupted her memory, Elizabeth might never be found. For several months, there was little or no progress on the case. Then, about 4 months after the kidnapping, Mary Katherine first recalled that she had heard the abductor’s voice prior to that night (he had worked one time as a handyman at the family’s home) and then she was able to name the person whose voice it was. The family contacted the press and others recognized him—after a total of nine months, the suspect was caught and Elizabeth Smart was returned to her family.

Elizabeth Loftus and the Misinformation Effect

Cognitive psychologist Elizabeth Loftus has conducted extensive research on memory. She has studied false memories as well as recovered memories of childhood sexual abuse. Loftus also developed the misinformation effect paradigm , which holds that after exposure to incorrect information, a person may misremember the original event.

According to Loftus, an eyewitness’s memory of an event is very flexible due to the misinformation effect. To test this theory, Loftus and John Palmer (1974) asked 45 U.S. college students to estimate the speed of cars using different forms of questions (Figure 2). The participants were shown films of car accidents and were asked to play the role of the eyewitness and describe what happened. They were asked, “About how fast were the cars going when they (smashed, collided, bumped, hit, contacted) each other?” The participants estimated the speed of the cars based on the verb used.

This video explains the misinformation effect.

You can view the transcript for “The Misinformation Effect” here (opens in new window) .

Participants who heard the word “smashed” estimated that the cars were traveling at a much higher speed than participants who heard the word “contacted.” The implied information about speed, based on the verb they heard, had an effect on the participants’ memory of the accident. In a follow-up one week later, participants were asked if they saw any broken glass (none was shown in the accident pictures). Participants who had been in the “smashed” group were more than twice as likely to indicate that they did remember seeing glass. Loftus and Palmer demonstrated that a leading question encouraged them to not only remember the cars were going faster, but to also falsely remember that they saw broken glass.

Photograph A shows two cars that have crashed into each other. Part B is a bar graph titled “perceived speed based on questioner’s verb (source: Loftus and Palmer, 1974).” The x-axis is labeled “questioner’s verb, and the y-axis is labeled “perceived speed (mph).” Five bars share data: “smashed” was perceived at about 41 mph, “collided” at about 39 mph, “bumped” at about 37 mph, “hit” at about 34 mph, and “contacted” at about 32 mph.

Figure 2 . When people are asked leading questions about an event, their memory of the event may be altered. (credit a: modification of work by Rob Young)

Studies have demonstrated that young adults (the typical research subjects in psychology) are often susceptible to misinformation, but that children and older adults can be even more susceptible (Bartlett & Memon, 2007; Ceci & Bruck, 1995). In addition, misinformation effects can occur easily, and without any intention to deceive (Allan & Gabbert, 2008). Even slight differences in the wording of a question can lead to misinformation effects. Subjects in one study were more likely to say yes when asked “Did you see the broken headlight?” than when asked “Did you see a broken headlight?” (Loftus, 1975).

Other studies have shown that misinformation can corrupt memory even more easily when it is encountered in social situations (Gabbert, Memon, Allan, & Wright, 2004). This is a problem particularly in cases where more than one person witnesses a crime. In these cases, witnesses tend to talk to one another in the immediate aftermath of the crime, including as they wait for police to arrive. But because different witnesses are different people with different perspectives, they are likely to see or notice different things, and thus remember different things, even when they witness the same event. So when they communicate about the crime later, they not only reinforce common memories for the event, they also contaminate each other’s memories for the event (Gabbert, Memon, & Allan, 2003; Paterson & Kemp, 2006; Takarangi, Parker, & Garry, 2006).

The misinformation effect has been modeled in the laboratory. Researchers had subjects watch a video in pairs. Both subjects sat in front of the same screen, but because they wore differently polarized glasses, they saw two different versions of a video, projected onto a screen. So, although they were both watching the same screen, and believed (quite reasonably) that they were watching the same video, they were actually watching two different versions of the video (Garry, French, Kinzett, & Mori, 2008).

In the video, Eric the electrician is seen wandering through an unoccupied house and helping himself to the contents thereof. A total of eight details were different between the two videos. After watching the videos, the “co-witnesses” worked together on 12 memory test questions. Four of these questions dealt with details that were different in the two versions of the video, so subjects had the chance to influence one another. Then subjects worked individually on 20 additional memory test questions. Eight of these were for details that were different in the two videos. Subjects’ accuracy was highly dependent on whether they had discussed the details previously. Their accuracy for items they had not previously discussed with their co-witness was 79%. But for items that they had discussed, their accuracy dropped markedly, to 34%. That is, subjects allowed their co-witnesses to corrupt their memories for what they had seen.

Controversies over Repressed and Recovered Memories

Other researchers have described how whole events, not just words, can be falsely recalled, even when they did not happen. The idea that memories of traumatic events could be repressed has been a theme in the field of psychology, beginning with Sigmund Freud, and the controversy surrounding the idea continues today.

Recall of false autobiographical memories is called false memory syndrome . This syndrome has received a lot of publicity, particularly as it relates to memories of events that do not have independent witnesses—often the only witnesses to the abuse are the perpetrator and the victim (e.g., sexual abuse).

On one side of the debate are those who have recovered memories of childhood abuse years after it occurred. These researchers argue that some children’s experiences have been so traumatizing and distressing that they must lock those memories away in order to lead some semblance of a normal life. They believe that repressed memories can be locked away for decades and later recalled intact through hypnosis and guided imagery techniques (Devilly, 2007).

Research suggests that having no memory of childhood sexual abuse is quite common in adults. For instance, one large-scale study conducted by John Briere and Jon Conte (1993) revealed that 59% of 450 men and women who were receiving treatment for sexual abuse that had occurred before age 18 had forgotten their experiences. Ross Cheit (2007) suggested that repressing these memories created psychological distress in adulthood. The Recovered Memory Project was created so that victims of childhood sexual abuse can recall these memories and allow the healing process to begin (Cheit, 2007; Devilly, 2007).

On the other side, Loftus has challenged the idea that individuals can repress memories of traumatic events from childhood, including sexual abuse, and then recover those memories years later through therapeutic techniques such as hypnosis, guided visualization, and age regression.

Loftus is not saying that childhood sexual abuse doesn’t happen, but she does question whether or not those memories are accurate, and she is skeptical of the questioning process used to access these memories, given that even the slightest suggestion from the therapist can lead to misinformation effects. For example, researchers Stephen Ceci and Maggie Brucks (1993, 1995) asked three-year-old children to use an anatomically correct doll to show where their pediatricians had touched them during an exam. Fifty-five percent of the children pointed to the genital/anal area on the dolls, even when they had not received any form of genital exam.

Ever since Loftus published her first studies on the suggestibility of eyewitness testimony in the 1970s, social scientists, police officers, therapists, and legal practitioners have been aware of the flaws in interview practices. Consequently, steps have been taken to decrease suggestibility of witnesses. One way is to modify how witnesses are questioned. When interviewers use neutral and less leading language, children more accurately recall what happened and who was involved (Goodman, 2006; Pipe, 1996; Pipe, Lamb, Orbach, & Esplin, 2004). Another change is in how police lineups are conducted. It’s recommended that a blind photo lineup be used. This way the person administering the lineup doesn’t know which photo belongs to the suspect, minimizing the possibility of giving leading cues. Additionally, judges in some states now inform jurors about the possibility of misidentification. Judges can also suppress eyewitness testimony if they deem it unreliable.

More on False Memories

In early false memory studies, undergraduate subjects’ family members were recruited to provide events from the students’ lives. The student subjects were told that the researchers had talked to their family members and learned about four different events from their childhoods. The researchers asked if the now undergraduate students remembered each of these four events—introduced via short hints. The subjects were asked to write about each of the four events in a booklet and then were interviewed two separate times. The trick was that one of the events came from the researchers rather than the family (and the family had actually assured the researchers that this event had not happened to the subject). In the first such study, this researcher-introduced event was a story about being lost in a shopping mall and rescued by an older adult. In this study, after just being asked whether they remembered these events occurring on three separate occasions, a quarter of subjects came to believe that they had indeed been lost in the mall (Loftus & Pickrell, 1995). In subsequent studies, similar procedures were used to get subjects to believe that they nearly drowned and had been rescued by a lifeguard, or that they had spilled punch on the bride’s parents at a family wedding, or that they had been attacked by a vicious animal as a child, among other events (Heaps & Nash, 1999; Hyman, Husband, & Billings, 1995; Porter, Yuille, & Lehman, 1999).

More recent false memory studies have used a variety of different manipulations to produce false memories in substantial minorities and even occasional majorities of manipulated subjects (Braun, Ellis, & Loftus, 2002; Lindsay, Hagen, Read, Wade, & Garry, 2004; Mazzoni, Loftus, Seitz, & Lynn, 1999; Seamon, Philbin, & Harrison, 2006; Wade, Garry, Read, & Lindsay, 2002). For example, one group of researchers used a mock-advertising study, wherein subjects were asked to review (fake) advertisements for Disney vacations, to convince subjects that they had once met the character Bugs Bunny at Disneyland—an impossible false memory because Bugs is a Warner Brothers character (Braun et al., 2002). Another group of researchers photoshopped childhood photographs of their subjects into a hot air balloon picture and then asked the subjects to try to remember and describe their hot air balloon experience (Wade et al., 2002). Other researchers gave subjects unmanipulated class photographs from their childhoods along with a fake story about a class prank, and thus enhanced the likelihood that subjects would falsely remember the prank (Lindsay et al., 2004).

Using a false feedback manipulation, we have been able to persuade subjects to falsely remember having a variety of childhood experiences. In these studies, subjects are told (falsely) that a powerful computer system has analyzed questionnaires that they completed previously and has concluded that they had a particular experience years earlier. Subjects apparently believe what the computer says about them and adjust their memories to match this new information. A variety of different false memories have been implanted in this way. In some studies, subjects are told they once got sick on a particular food (Bernstein, Laney, Morris, & Loftus, 2005). These memories can then spill out into other aspects of subjects’ lives, such that they often become less interested in eating that food in the future (Bernstein & Loftus, 2009b). Other false memories implanted with this methodology include having an unpleasant experience with the character Pluto at Disneyland and witnessing physical violence between one’s parents (Berkowitz, Laney, Morris, Garry, & Loftus, 2008; Laney & Loftus, 2008).

Importantly, once these false memories are implanted—whether through complex methods or simple ones—it is extremely difficult to tell them apart from true memories (Bernstein & Loftus, 2009a; Laney & Loftus, 2008).

Think It Over

Jurors place a lot of weight on eyewitness testimony. Imagine you are an attorney representing a defendant who is accused of robbing a convenience store. Several eyewitnesses have been called to testify against your client. What would you tell the jurors about the reliability of eyewitness testimony?

Problems with Memory. Authored by : OpenStax College. Located at : https://openstax.org/books/psychology-2e/pages/8-3-problems-with-memory . License : CC BY: Attribution . License Terms : Download for free at https://openstax.org/books/psychology-2e/pages/1-introduction
False Memories and more on the Misinformation Effect. Authored by : Cara Laney and Elizabeth F. Loftus . Provided by : Reed College, University of California, Irvine. Located at : http://nobaproject.com/textbooks/wendy-king-introduction-to-psychology-the-full-noba-collection/modules/eyewitness-testimony-and-memory-biases . Project : The Noba Project. License : CC BY: Attribution
The Misinformation Effect. Authored by : Eureka Foong. Located at : https://www.youtube.com/watch?v=iMPIWkFtd88 . License : Other . License Terms : Standard YouTube License

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21 Eyewitness Testimony and Memory Biases

Eyewitnesses can provide very compelling legal testimony, but rather than recording experiences flawlessly, their memories are susceptible to a variety of errors and biases. They (like the rest of us) can make errors in remembering specific details and can even remember whole events that did not actually happen. In this module, we discuss several of the common types of errors, and what they can tell us about human memory and its interactions with the legal system.

Learning Objectives

Describe the kinds of mistakes that eyewitnesses commonly make and some of the ways that this can impede justice.
Explain some of the errors that are common in human memory.
Describe some of the important research that has demonstrated human memory errors and their consequences.

What is Eyewitness Testimony?

Eyewitness testimony is what happens when a person witnesses a crime (or accident, or other legally important event) and later gets up on the stand and recalls for the court all the details of the witnessed event. It involves a more complicated process than might initially be presumed. It includes what happens during the actual crime to facilitate or hamper witnessing, as well as everything that happens from the time the event is over to the later courtroom appearance. The eyewitness may be interviewed by the police and numerous lawyers, describe the perpetrator to several different people, and make an identification of the perpetrator, among other things.

A man stands in front of a television camera and microphone as he describes an event he has witnessed.

Why Is Eyewitness Testimony an Important Area of Psychological Research?

When an eyewitness stands up in front of the court and describes what happened from her own perspective, this testimony can be extremely compelling—it is hard for those hearing this testimony to take it “with a grain of salt,” or otherwise adjust its power. But to what extent is this necessary?

There is now a wealth of evidence, from research conducted over several decades, suggesting that eyewitness testimony is probably the most persuasive form of evidence presented in court, but in many cases, its accuracy is dubious. There is also evidence that mistaken eyewitness evidence can lead to wrongful conviction—sending people to prison for years or decades, even to death row, for crimes they did not commit. Faulty eyewitness testimony has been implicated in at least 75% of DNA exoneration cases—more than any other cause ( Garrett, 2011 ). In a particularly famous case, a man named Ronald Cotton was identified by a rape victim, Jennifer Thompson, as her rapist, and was found guilty and sentenced to life in prison. After more than 10 years, he was exonerated (and the real rapist identified) based on DNA evidence. For details on this case and other (relatively) lucky individuals whose false convictions were subsequently overturned with DNA evidence, see the Innocence Project website ( http://www.innocenceproject.org/ ).

There is also hope, though, that many of the errors may be avoidable if proper precautions are taken during the investigative and judicial processes. Psychological science has taught us what some of those precautions might involve, and we discuss some of that science now.

Misinformation

In an early study of eyewitness memory, undergraduate subjects first watched a slideshow depicting a small red car driving and then hitting a pedestrian ( Loftus, Miller, & Burns, 1978 ). Some subjects were then asked leading questions about what had happened in the slides. For example, subjects were asked, “How fast was the car traveling when it passed the yield sign?” But this question was actually designed to be misleading, because the original slide included a stop sign rather than a yield sign.

Later, subjects were shown pairs of slides. One of the pair was the original slide containing the stop sign; the other was a replacement slide containing a yield sign. Subjects were asked which of the pair they had previously seen. Subjects who had been asked about the yield sign were likely to pick the slide showing the yield sign, even though they had originally seen the slide with the stop sign. In other words, the misinformation in the leading question led to inaccurate memory.

This phenomenon is called the misinformation effect , because the misinformation that subjects were exposed to after the event (here in the form of a misleading question) apparently contaminates subjects’ memories of what they witnessed. Hundreds of subsequent studies have demonstrated that memory can be contaminated by erroneous information that people are exposed to after they witness an event (see Frenda, Nichols, & Loftus, 2011 ; Loftus, 2005) . The misinformation in these studies has led people to incorrectly remember everything from small but crucial details of a perpetrator’s appearance to objects as large as a barn that wasn’t there at all.

These studies have demonstrated that young adults (the typical research subjects in psychology) are often susceptible to misinformation, but that children and older adults can be even more susceptible ( Bartlett & Memon, 2007 ; Ceci & Bruck, 1995 ). In addition, misinformation effects can occur easily, and without any intention to deceive ( Allan & Gabbert, 2008 ). Even slight differences in the wording of a question can lead to misinformation effects. Subjects in one study were more likely to say yes when asked “Did you see the broken headlight?” than when asked “Did you see a broken headlight?” ( Loftus, 1975 ).

Other studies have shown that misinformation can corrupt memory even more easily when it is encountered in social situations ( Gabbert, Memon, Allan, & Wright, 2004 ). This is a problem particularly in cases where more than one person witnesses a crime. In these cases, witnesses tend to talk to one another in the immediate aftermath of the crime, including as they wait for police to arrive. But because different witnesses are different people with different perspectives, they are likely to see or notice different things, and thus remember different things, even when they witness the same event. So when they communicate about the crime later, they not only reinforce common memories for the event, they also contaminate each other’s memories for the event ( Bernstein & Loftus, 2009b ; Paterson & Kemp, 2006 ; Takarangi, Parker, & Garry, 2006 ).

Identifying Perpetrators

In addition to correctly remembering many details of the crimes they witness, eyewitnesses often need to remember the faces and other identifying features of the perpetrators of those crimes. Eyewitnesses are often asked to describe that perpetrator to law enforcement and later to make identifications from books of mug shots or lineups. Here, too, there is a substantial body of research demonstrating that eyewitnesses can make serious, but often understandable and even predictable, errors ( Caputo & Dunning, 2007 ; Cutler & Penrod, 1995 ).

In most jurisdictions in the United States, lineups are typically conducted with pictures, called photo spreads , rather than with actual people standing behind one-way glass ( Wells, Memon, & Penrod, 2006 ). The eyewitness is given a set of small pictures of perhaps six or eight individuals who are dressed similarly and photographed in similar circumstances. One of these individuals is the police suspect, and the remainder are “ foils ” or “fillers” (people known to be innocent of the particular crime under investigation). If the eyewitness identifies the suspect, then the investigation of that suspect is likely to progress. If a witness identifies a foil or no one, then the police may choose to move their investigation in another direction.

A person wearing a red hood whose face is lit from underneath by a light making it hard to see their features.

This process is modeled in laboratory studies of eyewitness identifications. In these studies, research subjects witness a mock crime (often as a short video) and then are asked to make an identification from a photo or a live lineup. Sometimes the lineups are target present, meaning that the perpetrator from the mock crime is actually in the lineup, and sometimes they are target absent, meaning that the lineup is made up entirely of foils. The subjects, or mock witnesses , are given some instructions and asked to pick the perpetrator out of the lineup. The particular details of the witnessing experience, the instructions, and the lineup members can all influence the extent to which the mock witness is likely to pick the perpetrator out of the lineup, or indeed to make any selection at all. Mock witnesses (and indeed real witnesses) can make errors in two different ways. They can fail to pick the perpetrator out of a target present lineup (by picking a foil or by neglecting to make a selection), or they can pick a foil in a target absent lineup (wherein the only correct choice is to not make a selection).

Some factors have been shown to make eyewitness identification errors particularly likely. These include poor vision or viewing conditions during the crime, particularly stressful witnessing experiences, too little time to view the perpetrator or perpetrators, too much delay between witnessing and identifying, and being asked to identify a perpetrator from a race other than one’s own ( Bornstein, Deffenbacher, Penrod, & McGorty, 2012 ; Brigham, Bennett, Meissner, & Mitchell, 2007 ; Burton, Wilson, Cowan, & Bruce, 1999 ; Deffenbacher, Bornstein, Penrod, & McGorty, 2004 ).

It is hard for the legal system to do much about most of these problems. But there are some things that the justice system can do to help lineup identifications “go right.” For example, investigators can put together high-quality, fair lineups. A fair lineup is one in which the suspect and each of the foils is equally likely to be chosen by someone who has read an eyewitness description of the perpetrator but who did not actually witness the crime ( Technical Working Group for Eyewitness Evidence, 1999 ). This means that no one in the lineup should “stick out,” and that everyone should match the description given by the eyewitness. Other important recommendations that have come out of this research include better ways to conduct lineups, “double blind” lineups, unbiased instructions for witnesses, and conducting lineups in a sequential fashion (see Technical Working Group for Eyewitness Evidence, 1999 ; Wells et al., 1998 ; Wells & Olson, 2003 ).

Kinds of Memory Biases

Memory is also susceptible to a wide variety of other biases and errors. People can forget events that happened to them and people they once knew. They can mix up details across time and place. They can even remember whole complex events that never happened at all. Importantly, these errors, once made, can be very hard to unmake. A memory is no less “memorable” just because it is wrong.

Tall cases of books surround a central area full of desks as people sit reading and accessing information from computers in a public library.

Some small memory errors are commonplace, and you have no doubt experienced many of them. You set down your keys without paying attention, and then cannot find them later when you go to look for them. You try to come up with a person’s name but cannot find it, even though you have the sense that it is right at the tip of your tongue (psychologists actually call this the tip-of-the-tongue effect, or TOT) ( Brown, 1991 ).

Other sorts of memory biases are more complicated and longer lasting. For example, it turns out that our expectations and beliefs about how the world works can have huge influences on our memories. Because many aspects of our everyday lives are full of redundancies, our memory systems take advantage of the recurring patterns by forming and using schemata , or memory templates ( Alba & Hasher, 1983 ; Brewer & Treyens, 1981 ). Thus, we know to expect that a library will have shelves and tables and librarians, and so we don’t have to spend energy noticing these at the time. The result of this lack of attention, however, is that one is likely to remember schema-consistent information (such as tables), and to remember them in a rather generic way, whether or not they were actually present.

False Memory

Some memory errors are so “large” that they almost belong in a class of their own: false memories . Back in the early 1990s a pattern emerged whereby people would go into therapy for depression and other everyday problems, but over the course of the therapy develop memories for violent and horrible victimhood ( Loftus & Ketcham, 1994 ). These patients’ therapists claimed that the patients were recovering genuine memories of real childhood abuse, buried deep in their minds for years or even decades. But some experimental psychologists believed that the memories were instead likely to be false—created in therapy. These researchers then set out to see whether it would indeed be possible for wholly false memories to be created by procedures similar to those used in these patients’ therapy.

In early false memory studies, undergraduate subjects’ family members were recruited to provide events from the students’ lives. The student subjects were told that the researchers had talked to their family members and learned about four different events from their childhoods. The researchers asked if the now undergraduate students remembered each of these four events—introduced via short hints. The subjects were asked to write about each of the four events in a booklet and then were interviewed two separate times. The trick was that one of the events came from the researchers rather than the family (and the family had actually assured the researchers that this event had not happened to the subject). In the first such study, this researcher-introduced event was a story about being lost in a shopping mall and rescued by an older adult. In this study, after just being asked whether they remembered these events occurring on three separate occasions, a quarter of subjects came to believe that they had indeed been lost in the mall ( Loftus & Pickrell, 1995 ). In subsequent studies, similar procedures were used to get subjects to believe that they nearly drowned and had been rescued by a lifeguard, or that they had spilled punch on the bride’s parents at a family wedding, or that they had been attacked by a vicious animal as a child, among other events ( Heaps & Nash, 1999 ; Hyman, Husband, & Billings, 1995 ; Porter, Yuille, & Lehman, 1999 ).

More recent false memory studies have used a variety of different manipulations to produce false memories in substantial minorities and even occasional majorities of manipulated subjects ( Braun, Ellis, & Loftus, 2002 ; Lindsay, Hagen, Read, Wade, & Garry, 2004 ; Mazzoni, Loftus, Seitz, & Lynn, 1999 ; Seamon, Philbin, & Harrison, 2006 ; Wade, Garry, Read, & Lindsay, 2002 ). For example, one group of researchers used a mock-advertising study, wherein subjects were asked to review (fake) advertisements for Disney vacations, to convince subjects that they had once met the character Bugs Bunny at Disneyland—an impossible false memory because Bugs is a Warner Brothers character ( Braun et al., 2002 ). Another group of researchers photoshopped childhood photographs of their subjects into a hot air balloon picture and then asked the subjects to try to remember and describe their hot air balloon experience ( Wade et al., 2002 ). Other researchers gave subjects unmanipulated class photographs from their childhoods along with a fake story about a class prank, and thus enhanced the likelihood that subjects would falsely remember the prank ( Lindsay et al., 2004 ).

Using a false feedback manipulation, we have been able to persuade subjects to falsely remember having a variety of childhood experiences. In these studies, subjects are told (falsely) that a powerful computer system has analyzed questionnaires that they completed previously and has concluded that they had a particular experience years earlier. Subjects apparently believe what the computer says about them and adjust their memories to match this new information. A variety of different false memories have been implanted in this way. In some studies, subjects are told they once got sick on a particular food ( Bernstein, Laney, Morris, & Loftus, 2005 ). These memories can then spill out into other aspects of subjects’ lives, such that they often become less interested in eating that food in the future ( Bernstein & Loftus, 2009b ). Other false memories implanted with this methodology include having an unpleasant experience with the character Pluto at Disneyland and witnessing physical violence between one’s parents ( Berkowitz, Laney, Morris, Garry, & Loftus, 2008 ; Laney & Loftus, 2008 ).

To conclude, eyewitness testimony is very powerful and convincing to jurors, even though it is not particularly reliable. Identification errors occur, and these errors can lead to people being falsely accused and even convicted. Likewise, eyewitness memory can be corrupted by leading questions, misinterpretations of events, conversations with co-witnesses, and their own expectations for what should have happened. People can even come to remember whole events that never occurred.

The problems with memory in the legal system are real. But what can we do to start to fix them? A number of specific recommendations have already been made, and many of these are in the process of being implemented (e.g., Steblay & Loftus, 2012 ; Technical Working Group for Eyewitness Evidence, 1999 ; Wells et al., 1998 ). Some of these recommendations are aimed at specific legal procedures, including when and how witnesses should be interviewed, and how lineups should be constructed and conducted. Other recommendations call for appropriate education (often in the form of expert witness testimony) to be provided to jury members and others tasked with assessing eyewitness memory. Eyewitness testimony can be of great value to the legal system, but decades of research now argues that this testimony is often given far more weight than its accuracy justifies.

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A memory error caused by exposure to incorrect information between the original event (e.g., a crime) and later memory test (e.g., an interview, lineup, or day in court).

A selection of normally small photographs of faces given to a witness for the purpose of identifying a perpetrator.

Any member of a lineup (whether live or photograph) other than the suspect.

A research subject who plays the part of a witness in a study.

A memory template, created through repeated exposure to a particular class of objects or events.

Memory for an event that never actually occurred, implanted by experimental manipulation or other means.

An Introduction to Social Psychology Copyright © 2022 by Thomas Edison State University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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The Handbook of Eyewitness Psychology: Volume I

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The Handbook of Eyewitness Psychology presents a survey of research and legal opinions from international experts on the rapidly expanding scientific literature addressing the accuracy and limitations of eyewitnesses as a source of evidence for the courts. For the first time, extensive reviews of factors influencing witnesses of all ages-children, adults, and the elderly-are compiled in a single pair of volumes. The disparate research currently being conducted in eyewitness memory in psychology, criminal justice, and legal studies is coherently presented in this work. Controversial topics such as the use of hypnosis, false and recovered memories, the impact of stress, and the accuracy of psychologically impaired witnesses are expertly examined. Leading eyewitness researchers also discuss the subjects of conversational memory, alibi evidence, witness credibility, facial memory, earwitness testimony, lineup theory, and expert testimony. The impact of witness testimony in court is considered, and each volume concludes with a legal commentary chapter. The Handbook of Eyewitness Psychology is an invaluable aid to researchers, legal scholars, and practicing lawyers who need access to the most recent research in the field, accompanied by the interpretations and commentary of many of the world's leading authorities on these topics.

Part i | 2 pages, forensic adult memory of witnesses and suspects, chapter 1 | 50 pages, memory for conversation: the orphan child of witness memory researchers, chapter 2 | 28 pages, interview protocols to improve eyewitness memory, chapter 3 | 36 pages, the influence of emotion on memory in forensic settings, chapter 4 | 40 pages, the effects of delay on long-term memory for witnessed events, chapter 5 | 18 pages, alibis in criminal investigations and trials, chapter 6 | 18 pages, internalized false confessions, part ii | 2 pages, potential sources of distorted eyewitness statements and postdictors of statement accuracy, chapter 7 | 44 pages, internal and external sources of misinformation in adult witness memory, chapter 8 | 22 pages, false memory research: history, theory, and applied implications, chapter 9 | 38 pages, psychological impairment, eyewitness testimony, and false memories: individual differences, chapter 10 | 22 pages, recovered memories, chapter 11 | 18 pages, using hypnosis in eyewitness memory: past and current issues, chapter 12 | 32 pages, credibility assessment in eyewitness memory, chapter 13 | 28 pages, eyewitness confidence from the witnessed event through trial, part iii | 2 pages, lifespan eyewitness issues: children, chapter 14 | 28 pages, the suggestibility of children’s memory, chapter 15 | 24 pages, enhancing performance: factors affecting the informativeness of young witnesses, chapter 16 | 26 pages, the development of event memory: implications for child witness testimony, chapter 17 | 30 pages, false memory in children: data, theory, and legal implications, chapter 18 | 36 pages, a review of factors affecting jurors’ decisions in child sexual abuse cases, chapter 19 | 27 pages, children’s eyewitness memory: balancing children’s needs and defendants’ rights when seeking the truth, part iv | 2 pages, lifespan eyewitness issues: older adults, chapter 20 | 28 pages, the elderly eyewitness: a review and prospectus, chapter 21 | 22 pages, false memory susceptibility in older adults: implications for the elderly eyewitness, chapter 22 | 20 pages, eyewitness memory in older adults, part v | 2 pages, chapter 23 | 20 pages, the relevance of eyewitness research: a trial lawyer’s perspective.

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Eyewitness Imagination: How Our Minds Change Our Memories

Eyewitness memory can be inaccurate. but can it change itself.

Posted September 11, 2020 | Reviewed by Devon Frye

In our last Forensic View, we saw that typical eyewitness errors follow an interesting pattern. The most common eyewitness errors are those of suspect appearance, which is not surprising.

However, the second most common errors are those of the imagination . This is more surprising, and a lot scarier. The frequency of imaginative errors was far beyond those of any other error type (errors of suspect race or sex , or of weapons used, or of important elements of the physical environment of a given crime ). Far beyond error rates in any of these important areas, people simply made things up . And they had no idea they were doing it.

How is this possible? Well, it has directly to do with how memory works, rather than with how most people think memory works.

As we’ve discussed in previous Forensic Views , people tend to think of memory as immutable, as some kind of essentially accurate recording we make in the brain (accurate except for the bits that drop out completely, bits which we term “forgotten"). But as we’ve also discussed (Bartlett, 1932; Sharps, 2017), psychologists have known that this popular view is incorrect for most of a century. Bartlett showed that memories are not static, but that they reconfigure in three specific ways: they become shorter, they coalesce around the gist of what actually happened, and they change in the direction of personal belief. This is the really scary one: we tend to remember what we believe happened, not what actually happened.

This fact throws the importance of forensic cognitive psychology into sharp relief. What we remember is not only dependent on physical reality . It also depends on what we think happened in a given situation; and, as we will see, the resultant inaccuracies can be further exacerbated by the nature of the memory process itself.

In research in my laboratory, eyewitness performance is frequently awful. For example, under ideal viewing conditions, people were right less than half the time when they tried to identify a gun they saw earlier, and right less than a quarter of the time when they tried to identify a car (see Sharps, 2017, for review). So, given this genuinely horrible level of eyewitness performance, we began to explore possible sources of eyewitness error. We began to ask: how is eyewitness memory actually elicited in a criminal investigation?

In any investigation, witnesses are going to be asked for their stories repeatedly. Officers at initial contact will ask questions. Then will come sergeants, then detectives, then more detectives, then district attorney investigators, then an assistant district attorney, then a public defender investigator, then a public defender, then a prosecutor in court—a given witness may have to think about his or her memories of a criminal situation many times, not even counting the number of times he or she thought about these issues alone, or recounted them to spouse, parents, or friends.

But why would this matter?

We conducted an experiment (Sharps et al., 2012) in which we did the same type of repeated questioning to which the criminal justice system would subject any witness. We used an experimental scene we have used many times, in which a “suspect” appears to be aiming a firearm at a “victim.” We exposed 92 people, under ideal viewing conditions (generally much better than those of a typical eyewitness situation) to this scene, and we asked them what they saw. We did this repeatedly, as occurs in the real world; our first request for information was followed by three more requests, for the ostensible purpose of adding any additional details the witnesses might recall.

Now, recall that Bartlett showed that memories are not static recordings, but are reconfigured in the directions of gist, brevity, and personal belief. Also, please recall that in our research, errors of the imagination, rooted not in the real world but in the activity of the mind itself , were the second most common error type (see Sharps, 2017).

Our witnesses of course gave accounts of the criminal event they saw initially. But what’s important to realize here is that every time eyewitnesses give an account of a crime, their recounting of that crime is also an event, subject to the same laws of Bartlett reconfiguration .

This means that every time you tell somebody about something, your retelling, as an event, may influence future accounts. Your imagination today can influence your imagination tomorrow.

But does it?

In our experiment (Sharps et al., 2012), our first request for information resulted in a true/false ratio of 3.56; in other words, we got about three and a half true statements for every false one. Not great, obviously, but not too bad.

However, our second ratio was a lot worse, with only 1.39 correct facts for every false one. The fourth question gave us similar results to the second; people were coming in with almost as many false statements as true ones. But on question 3, things were a whole lot worse: we got more false statements than true ones!

Repeating the story resulted in more and more errors, exactly as we’d predict by seeing repetition not as a passive act, but as an active contributor to inaccuracy.

Memories are not static recordings; well and good. But it turns out that memories can actually change themselves, simply by the repeated act of being remembered! And as a result, memory itself can alter the later memories recounted by a given eyewitness; memories on which a completely erroneous conviction of an innocent person may be based.

This is yet another demonstration of the great importance of an understanding of psychology, including forensic cognitive psychology, to the effectiveness and fairness of the criminal justice system.

Bartlett, F.C. (1932). Remembering: A Study in Experimental and Social Psychology. Cambridge: Cambridge University Press

Sharps, M.J. (2017). Processing Under Pressure: Stress, Memory, and Decision-Making in Law Enforcement. Flushing, NJ: Looseleaf Law

Sharps, M.J., Herrera, M., Dunn, L., & Alcala, E. (2012). Recognition and Reconfiguration: Demand-Based Confabulation in Initial Eyewitness Memory. Journal of Investigative Psychology and Offender Profiling, 9, 149-160.

Matthew Sharps, Ph.D., professor of psychology at California State University, Fresno. He researches forensic cognitive science among other related areas.

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How to improve eyewitness testimony research: theoretical and methodological concerns about experiments on the impact of emotions on memory performance

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Published: 19 February 2021
Volume 86 , pages 1–11, ( 2022 )

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The purpose of this paper is to present crucial shortcomings of research into eyewitness testimony. It presents the state-of-the-art of research on the relationship between emotions and memory performance. In addition, it addresses contradictions and concerns about previous studies. Despite the declarations of consensus on the role of emotions in memory coding and retrieving, there are as many studies suggesting that emotional events are better remembered than neutral ones, as there are reports that show the opposite. Therefore, by indicating the theoretical and methodological limitations of previous studies, this paper advocates a more rigorous approach to the investigation of emotions and their impact on the quality and quantity of testimony. It also provides a framework for inquiry that allows better comparisons between studies and results, and may help to build a more comprehensive theory of the effects of emotion on memory

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Introduction

Eyewitnesses often make mistakes, misreport and misidentify; thus, some of them are unreliable sources of information. There is hardly a textbook on the psychology of eyewitness testimony that suggests otherwise. After more than 40 years of research on memory relating to criminal events, this notion is increasingly accepted outside the field of academic psychology and influences legal proceedings and decisions.

However, with growing awareness of human memory limitations and its consequences for eyewitness testimony comes a discussion about the status of knowledge based on laboratory research. For many decades, almost every empirical article in the field discusses shortcomings of research. Yet, they rarely include practical guidelines on how to improve research. As a consequence of questionable methodological basis, there is no shortage of controversy over conflicting results. This seems particularly evident in the case of research on the influence of emotions on eyewitness testimony, which only superficially seems to have been resolved.

The purpose of this paper is to draw attention to the shortcomings of laboratory research concerning the effect of emotions on memory performance, and to analyse the consequences for comprehension and the application of empirical findings. Moreover, it will address them by suggesting a theoretical and methodological framework that may benefit research and serve as general guidelines for improving the quality of studies. In consequence, it will be easier to draw solid, well-grounded conclusions about the role of emotions in memory performance.

It should be noted that this paper is not a systematic review of the issue. Readers interested in more general knowledge on the application of eyewitness testimony research may refer to other papers available in the literature (e.g. Chae, 2010 ; Kassin, Tubb, Hosch, & Memon, 2001 ; Wagstaff, MaCveigh, Boston, Scott, Brunas-Wagstaff, & Cole, 2003 ).

What do we know about emotions and eyewitness testimony?

Eyewitness testimony is a legal term that refers to an account of a crime given by an individual who has seen or been involved in that event. It often includes not only bystanders but also victims. Eyewitness testimony can have different forms, from a description of an event or a perpetrator, to the identification of suspects or important objects such as weapons or vehicles. For many decades, research on eyewitness testimony has focused on the identification of individual, situational, environmental, and system variables that impact the quality and quantity of testimony. Consequently, we acknowledge now that eyewitness evidence may not be as reliable as we used to think.

Among estimator variables, a category including factors that discount or augment the credibility of eyewitnesses (Wells, 1978 ), which can be only considered post factum, emotions are often discussed. Crime is a stressful experience for victims and for witnesses. Even an accidental bystander may become emotionally involved. The common suspicion and distrust we have about emotions and people showing them have led us to consider them a source of memory errors. However, as we will see, studies do not always confirm this notion.

The question of how emotions impact the way criminal events are remembered was first asked by pioneers of applied psychology. One of the first experiments on the subject, described in Münsterberg's essay ( 1908 /2009), was conducted by von Liszt at the University of Berlin, at the beginning of the twentieth century. The experiment, which simulated a life-threatening situation, showed that memories of unexpected events accompanied by fear and a sense of danger are more distorted and misreported than emotionally neutral events.

There are many more recent studies that support this claim. It is considered that stressful stimuli negatively impact memory of perpetrator characteristics, pertinent actions, and details of crime scenes. The notion is evidenced by laboratory experiments and case studies (Clifford & Hollin; 1981 , Kuehn, 1974 ; Loftus & Burns, 1982 , Southwick, Morgan, Nicolaou, & Charney, 1997 , Takahashi, Itsukushima & Okabe, 2006 ; for a meta-analysis see Deffenbacher, Bornstein, Penrod, & McGorty, 2004 ). It is possible that negative emotions have detrimental effects on the reconsolidation of episodic memory through stress hormones (Schwabe & Wolf, 2010 ). Footnote 1 In consequence, as Bornstein and Robicheaux ( 2008 , p. 525) state: “the expert consensus on eyewitness memory and arousal is that in most respects, arousal exerts a negative effect on eyewitness performance”.

However, if we take a closer look at the research results, the only obvious thing is that the influence of emotions on testimony is far from obvious. There seems to be as much evidence of the negative impact of emotions on the reliability of eyewitness testimony as there is evidence to the contrary. Empirical findings suggest that memory of stressful events tends to be accurate, as evidenced by research in eyewitness testimony (e.g. Block, Greenberg & Goodman, 2009 ; Christiansona & Hübinette, 1993 ; Christianson et al., 1991 ; Houston, Clifford, Phillips, & Memon, 2013 ; Maras, Gaigg & Bowler, 2012 ; Smeets, Candel & Merckelbach, 2004 ), as well as in the more general approach (e.g. Anderson, Wais & Gabrieli, 2006 ; Bookbinder & Brainerd, 2017 ; Bradley, Greenwald, Petry & Lang, 1992 ; Kensinger, Garoff-Eaton & Schacter, 2007 ; Laney, Campbell, Heuer & Reisberg, 2004 ).

A good example of the difficulties in reconciling research results is the issue of the weapon focus effect (WFE), a phenomenon describing the allocation of attention resources on highly emotive, threatening objects and, in consequence, reduced ability to describe or identify an offender and other details of the event. The overall significant difference in identification accuracy in weapon-present and weapon-absent conditions has been demonstrated (Steblay, 1992 ; Fawcett, Russell, Peace & Christie, 2013 ). However, Hulse and Memon ( 2006 ) showed that, while the presence of a weapon increases arousal, it does not always inhibit recognition accuracy. Some studies also suggest that the effect may not be as general as usually presented (e.g. Carlson & Carlson, 2012 ).

Therefore, the only consensus we can acknowledge is on the differences in remembering emotional versus neutral stimuli. Especially as it is supported by evidence showing distinct neural patterns of information processing depending on the stimulus valence and arousal (Kensinger & Corkin, 2004 ).

In the light of many contradicting results, questions about their applicability outside laboratory settings, and concerns about the validity of conditions and mental states created in a lab, the debate about the current state-of-the-art of eyewitness testimony research is hardly surprising. However, acknowledgment that the research on eyewitnesses’ emotions may not reflect reality is only the starting point. The next step would be to discuss possible reasons why we are still unsure how to estimate the impact of emotions experienced by eyewitnesses on their memory performance.

How eyewitness testimony research goes astray

Two separate issues should be considered when systematising knowledge in this field. The first concerns the way memory is studied and discussed. In the author's opinion, contradictions are essentially the result of excessive simplifications in the presentation of research results, and of too far-reaching conclusions drawn from examination of a particular memory process. It seems that the influence of emotions on memory may not be broad and general, as it is sometimes portrayed. The impact seems to vary depending on memory function under investigation (recollection and recognition), the paradigm used to test memory (free recall, structured recall, etc.) and the content of a memory (central versus peripheral details, faces versus objects, etc.). Considering those nuances in study reports should be a common practice rather than a brief element of research discussion.

The second issue concerns emotions. While analysing research papers on the relations between affective states and memory performance, one may conclude that the vast body of theoretical and empirical studies on emotions are taken into account insufficiently. Thus, this paper will discuss three major issues concerning the way emotions are addressed and investigated in eyewitness testimony research, and which may be why we face difficulties when comparing study results. These concerns involve the way emotions are (1) defined, (2) induced and (3) measured in laboratory settings.

Defining emotions

It is a convenient truism that emotions are difficult to define. As interest in research on emotions intensified in the late 1980s, almost every major theorist developed a distinctive concept of what emotions are and how they differ from other related affective states, such as moods or attitudes. The wealth of terms and definitions should not, however, be an excuse to ignore the body of knowledge related to the theory of emotions. Unfortunately, it is common to get the impression that, in the case of forensic psychology experiments, the word “emotion” is considered self-defining—a concept that needs no further explanation.

Typically, most research investigating human emotions falls into one of two theoretical categories—discrete or dimensional. The first approach views emotions as specific affective states that can be labelled (e.g. anxiety, fear, anger, etc.), while the other describes them according to the dimensional space of their core properties—valence, arousal, and less often, dominance. Even though it cannot be said that one or the other is more or less correct, the dimensional approach is more likely to focus on the fundamental organisation of emotions (Scherer, 2005 ). When this approach is employed, at least two affective dimensions (arousal and valence) should also be considered. However, studies are typically focused on one or the other (Bradley, 1994 ).

The lack of precision in defining the area of interest is noticeable in eyewitness testimony research. A wide range of terms is used to name affective states, such as negative emotions, arousal or stress. There is often no reflection on what these terms imply, or on the theoretical methodological consequences of their use. When we look more closely at research subjects and objectives, we can see that the terms chosen for independent variables are rarely set within the theoretical framework. Furthermore, they only seemingly relate to the approaches described above. In consequence, as the concepts are used arbitrarily and thoughtlessly, some studies answer questions other than those which they ask.

Negative emotion

When using the term negative emotion, emphasis seems to be on the valence—the subjective meaning an individual gives to a stimulus. However, eyewitness testimony research commonly uses the term primarily to investigate the discrete emotions—fear, anger, anxiety—not the pleasant–unpleasant dimension. It serves as a category that includes basic/modal emotions that are a priori associated with unpleasant experiences. The term also seems to describe the implicit negative tone of the criminal event, not the affective state of an eyewitness per se .

However, a research problem formulated in this fashion entails the risk of investigating artifacts. As particular negative emotions differ in terms of their properties, function, and behavioural and physiological reactions, it is the author’s opinion they may influence memory coding in distinct ways. The category includes very different affective states (such as anger/rage and fear/anxiety), yet equating them and studying them as one may provide misleading results. For example, during experimental manipulation one subject may experience fear/anxiety, while another feels anger, with both labelled ‘negative emotion’. In quantitative studies, the impact of the first may be neutralised by the very different effect caused by the latter. Anger serves as preparedness for attack, as motivation to approach the stimulus. Fear/anxiety, on the other hand, evokes the behavioural tendency to escape or avoid the stimulus. In consequence, while the subject experiencing anger may be strongly focused on the stimulus that caused it, the other may divert their attention away from the stimulus. Thus, the inconclusive study results.

It is also reasonable to ask which of these discrete emotions (or rather, what kind of their configuration) reflect the actual experiences of eyewitnesses and can, therefore, serve as the best analogy of those experiences. Intuition suggests that, when a witness observes a situation in which someone suffers physical harm or threat to life, they first experience fear/anxiety. Seeing a verbal, non-physical attack may cause anger rather than fear. Thus, when adopting the discrete approach, it seems crucial to analyse the impact of emotions on testimony in a more nuanced way. Considering the term “negative emotion” collectively does not necessarily explain the relationship between affective state and memory, nor does it provide insight into eyewitness experience.

On the other hand, if the concept of negative emotion is used in terms of the dimensional approach, it may have different implications for research design. While drawing attention to the subjective valence of emotional experience, the next logical step would be to examine how memory is affected depending on stimulus assessment on a scale from unpleasant to pleasant. Moreover, as the psychology of eyewitness testimony is interested in unpleasant events, it would be ideal to differentiate the level of unpleasantness of stimuli by manipulating it from the least unpleasant to the most unpleasant. This approach would facilitate accurate and appropriate investigation into valence.

However, to examine how negative emotions impact memory, it is crucial to create an event that truly evokes the required emotional reaction. Given ethical constraints, laboratory experiments may not include a stimulus that evokes negative emotions—only one that does not evoke positive ones. There is also a possibility that the reaction of a subject exposed to a stimulus is not at all an emotion but a startlement or surprise, which are, for some scholars, instinctive reactions (e.g. Ekman, Friesen & Simon, 1985 ).

To sum up, it is suggested that, if the term negative emotion in fact applies the discrete approach, a study should examine the variations between the influence of different types of emotions on the reliability of eyewitness testimony. In addition, research into the valence dimension should focus on how experiences evaluated as unpleasant are remembered, compared to neutral and pleasant ones.

Besides negative emotions, a term frequently used in eyewitness testimony research to describe an affective state is arousal . Arousal, along with valence, is considered a core dimension of emotional experience. The ability to evoke arousal distinguishes between emotions and other affective states, e.g. moods and attitudes, and fuels further action (Frijda, 2004 ). It is a psychophysiological reaction to a stimulus, representing the activation of the autonomic nervous system (ANS). Thus, a study involving arousal may examine an objectively measurable state, not only an individual's subjective assessment. It is even more important, as some studies show, that self-reporting of arousal may differ from an objective measurement of ANS activation (e.g. Chivers, Seto, Lalumiere, Laan & Grimbos 2010 ; Salimpoor, Benovoy, Longo, Cooperstock & Zatorre, 2009 ).

In eyewitness testimony, research into arousal is often (although not exclusively) associated with the weapon focus effect. Thus, even though arousal is a neutral state, it is in eyewitness testimony research sometimes defined as negative (e.g. MacLin, MacLin & Malpass, 2001 , Luna & Martin-Luengo, 2018 ) or as having implicit negative valence as it is evoked by unpleasant (crime-related) stimuli (e.g. Hämmerer et al, 2017 ).

This implicit negative valence may explain why, in contrast to general research on the arousal–memory relationship that suggests increased accuracy of recollection of arousing stimuli (e.g. Bradley et al., 1992 ), some experiments in forensic psychology show that arousal has a negative influence on eyewitness memory (e.g. Carlson, Dias, Weatherford & Carlson, 2017 ). However, it is important to underline alternative explanations that focus on the differences between central versus peripheral details (e.g. Kensinger, 2009 ), as well as the interview procedure (e.g. Quas & Lench, 2007 ).

When analysing studies on arousal and eyewitness testimony, we can also notice that arousal is often treated as a nominal variable. Subjects are induced into high-arousal or low-arousal/non-arousal states. Yet, arousal as a physiological reaction can be accurately measured. Thus, research does not need to limit its inference to a reduced problem. The issue of objective measures of emotional experience is further elaborated in the subsection on emotion measurements.

To sum up, it is postulated, that research should, in terms of arousal, focus primarily on examining how different levels and patterns of ANS activity affect the processing of visual information and its coding in long-term memory. It is also important to keep in mind that arousal is fundamentally neutral, but can be evoked by stimulus with negative, neutral and positive valence.

The lack of precision in the use of terms in eyewitness testimony research is even more evident when we look at the term stress . One may feel that research on the eyewitness testimony mimics trends in society at large, in which the term is applied to describe very different mental states—anxiety, fear, frustration, fatigue, sense of overwhelming or even anger. However, in eyewitness testimony research stress seems to describe properties of stimulus rather than eyewitness affective state. It is often a threatening, violent or demanding situation in which an individual often feels fear/anxiety or experiences arousal . However, this stimulus-based conceptualisation of stress is questionable, as it ignores the core concept of psychological stress—individual differences in coping with stimuli.

Applying the concept of psychological stress scientifically has its theoretical connotations and methodological consequences. Established theories and models of stress usually focus on the relationship between the external demands of the stressor and an individual’s coping mechanism. One of the most prominent theories of stress, formulated by Lazarus (Lazarus & Launier, 1978 ), views stress as a relational concept, a form of transaction between a person and an environment. It emphasises the individual’s appraisal of the significance of the stimulus in relation to how it threatens subjectively-defined well-being, and whether available coping resources are enough to deal with this threat (Lazarus & Folkman, 1986 ). Therefore, the term stress should be used neither to describe a specific external stimulation (as it is not synonymous with negative stimulus) nor to define a specific pattern of emotional, physiological or behavioural reactions.

With this in mind, it is the author’s opinion that research on stress and memory should be focused on individual differences, in particular examining why, for some eyewitnesses, stressful events are remembered better, while others tend to misrepresent events and misidentify suspects.

Even though emotions are the focal point of the paper, the issue of chronic moods requires a brief comment, as it is also a subject of research on eyewitness testimony. However, it is crucial to understand the difference between moods and emotions. While the latter are considered short, rapidly transient and intense affective states caused by a specific internal and external stimulus, moods are harder to define in terms of specific cause. As Frijda ( 1994 , p. 59) believes, their object is 'the world as a whole'. They are also chronic and slowly passing, thus the disposition to experience a given mood allows us to draw conclusions about an individual’s personality (Meyer & Shack, 1989 ).

Despite this clear distinction, many empirical studies use these concepts interchangeably. It is quite possible that arbitrary application of these terms may be a legacy of research on the mood-state dependent effect. In his classical paper on associative network theory, Bower ( 1981 ) evokes happiness and sadness, and uses the terms “emotions” and “moods”, to name those states. Since imagination guided by hypnotic suggestion was employed to induce them, mood is the term which seems more appropriate to describe the experience. Confusion also concerns the use of terms “sadness” and “happiness”, which are more often used to label discrete emotions than moods.

Thus, it is postulated to use distinctive terms for short affective states evoked in response to specific stimulus, and for chronic, general, diffuse affective state, which can be considered a disposition to experience certain emotions (mood-trait) or a long-lasting affective state (mood-state). Moreover when the mood type is taken into account, it is advised to use adjectives describing the valence of the mood, for example “depressive mood” rather than “sadness”, or “elated mood” rather than “joy” or “happiness”. As some evidence suggests that chronic moods may also influence eyewitness testimony, thus control for a dispositional mood can be also considered.

To sum up the deliberations on defining emotions, it is important to highlight the misuse of terms and concepts of emotions, with little regard to theory and achievements of research on emotions. Thus, it is postulated that a study should define the spectrum of affective experience precisely and in accordance with the chosen theoretical approach. It must go hand in hand with awareness of the consequences of that choice, imposed by the research subject and methodology. Moreover, although both approaches to study emotions have their justification in the theory of emotions, it seems that in the case of eyewitness testimony research, the most appropriate would be to combine both. On the one hand, it would allow us to indicate what feelings accompany witnesses depending on the type of crime observed (discrete approach). On the other, dimensional approach may help to determine the characteristics of the emotional stimulus which seems to be particularly threatening the reliability of the testimony.

Inducing emotions

Another area of doubt concerning research on eyewitness testimony is related to experimental manipulation, particularly the methods of inducing affective states. In experiments conducted in psychological labs, short films or movie clips presenting a simulated crime are the most frequently employed emotive stimuli. In fewer instances, a crime is staged, making the subjects real eyewitnesses to a false event. Researchers also use slide presentations with short narratives or photographs. Other methods of inducing emotion include exposure to aversive stimuli, such as threat of an injection or mild electric shocks (see Deffenbacher et al., 2004 ).

In research on chronic mood and its impact on eyewitness testimony, a different approach is often employed. Moods may be induced by techniques such as hypnotic suggestion, instruction to recall past events, reading statements related to certain moods (e.g. the Velten Mood Induction Procedure) or listening to music. In other cases, a different methodological approach with quasi-experimental research and subjects recruited on the basis of their dispositional mood or mood disorders (e.g. depression) is adopted.

While focusing on emotions, the fundamental question when evaluating research design is whether such experimental manipulations are sufficient to evoke real emotions, similar to those experienced by eyewitnesses and consequently, the extent to which experimental studies can be generalised in the forensic context. As Yuille and Tollestrup ( 1992 ) argue, a typical laboratory eyewitness is a passive observer, not experiencing a sense of danger or involvement in the event. Their physical and psychological well-being is not under threat. Thus, the behaviour of witnesses in this setting is not representative of that of witnesses to actual crimes. With this in mind, one should consider what type of stimulus manipulation increases the chances of evoking real emotions, not just a declaration of emotions.

In the author’s opinion, the strength of manipulation is derived from the level of the subject’s involvement in a study. Thus, in order to induce states as similar as possible to those experienced by real eyewitnesses, the distance (both physical and psychological) between subject and stimulus should be minimised. This kind of approach is widely used in social psychology, noted for psychologically meaningful, high impact experimental manipulations (Amodio, Zinner & Harmon-Jones, 2007 ). However, it may be difficult to achieve through short films, presentations or photos presented on a TV or computer screen.

Although there is evidence that films can induce emotions, and they are widely regarded as ecologically valid stimuli, they must meet several conditions. After examination of movie databases serving as archives of stimuli useful in laboratory studies (e.g. Carvalho, Leite, Galdo-Álvarez & Gonçalves, 2012 ; Gross & Levenson 1995 ), it can be concluded that the most effective ones are expressive and emotionally unambiguous. The duration of the video clip may also be meaningful. Most databases include clips that last from 40 s to less than three minutes, but Gross and Levenson’s ( 1995 ) research indicates that films longer than a few dozen seconds have a better chance of evoking emotions, especially more complex ones. Footnote 2

The hypothetical mechanism explaining how movies can influence emotions, and in consequence beliefs, attitudes, or behaviour, is the transportation into narrative effect. This describes psychological immersion into a narrative, and its effect is particularly pronounced when the emotional state of individual pre-reading or pre-watching content is consistent with the emotional tone of the narrative (e.g. Green, Chatman & Sestir, 2012 ). It seems that videos capable of inducing this effect have a greater chance of evoking emotional experiences comparable to those of eyewitnesses. However, it is difficult to meet these criteria with videos lasting 30–40 s, devoid of context and lacking vivid, identifiable characters with whom a viewer can form an empathic bond, which seems to be an important component of an emotional experience of a film (Tan, 1995 ).

Therefore, it is postulated that, when a crime event is presented via video, it should be an engaging narrative that focuses the subject’s attention. It would also be good practice to assess the film before the experiment (in a pilot study) or after the presentation (manipulation check), to investigate its impact on at least three-dimensional space, which represents the valence of the stimulus, the intensity of subjectively perceived excitement, and the dominance (the degree to which the film was involving and allowed subjects to detach from external stimuli).

Virtual reality

Another way to simulate eyewitness experience in the safe and controllable setting of a laboratory is to use modern technologies. Virtual reality (VR) with high-quality equipment provides a great opportunity for research into memory, as it allows the creation of a complex and rich environment that is fully under the control of the researcher. As goggles cut off external stimuli, VR minimises the distance between the observer and the scene, which increases immersion and allows transportation into a fictional event. Moreover, as many studies show, emotional, behavioural, and social reactions of people are the same in virtual reality as in everyday life (e.g. Gamberini et al. 2015 ; Kozlov & Johansen, 2010 ; Riva et al. 2007 ). With today's technological capabilities and relatively inexpensive equipment, VR may serve as a substitute not only for insufficiently involving films or video clips, but also field studies, hazardous because of possible uncontrolled variables affecting the result.

This method of experimental manipulation is nothing new. It has been successfully employed in many fields, eyewitness testimony included (e.g. Kloft et al, 2020 ). A particularly interesting approach is to use tools that are already utilised in law enforcement training, based on real-life simulators or large-screen video projections, not a programmed, thus artificial environment (e.g. Hulse & Memon, 2006 ; Stanny & Johnson, 2000 ). Provided they use equipment at the highest technological level, they can be highly realistic and involving, and thus, simulating a real experience.

Staged crime/live events

It seems that the most reliable way to simulate the experience of real eyewitnesses is to expose subjects to staged crime. Even though the crime is faked, an individual may for a moment experience real emotions, thus it meets the criteria of high ecological validity. The choice of such a method seems even more appropriate in the light of the evidence of differences in testimonies concerning live and recorded events (Ihlebæk, Løve, Erik Eilertsen & Magnussen, 2003 ). This kind of experimental manipulation is particularly useful in group conditions, where all participants watch the same event. Considering the high demands on the sample numbers, it may be harder to reproduce an identical event for a single participant. When deciding on this type of experimental manipulation, it is crucial to consider all ethical concerns as well.

To sum up the subsection on inducing emotion in a laboratory setting, it is crucial to underline the need to simulate experiences resembling (at least to some extent) those of witnesses to the crime. This can be achieved when experimental manipulation meets several criteria: (1) the stimulus is subjectively meaningful for the subjects; (2) psychological and physical (even imagined) distance between stimulus and observer is short; (3) regardless of the chosen way of presenting the crime event, subjects find it absorbing, (4) emotions and involvement are meticulously examined. This approach avoids the risk of drawing incorrect conclusions about the relationship between emotions and memory based on ineffective stimulus manipulation, or on one that induces states other than those intended.

Measuring emotions

The choice of theoretical background in research on the impact of emotions on eyewitness testimony should have consequences related not only to how research questions are formulated and hypotheses tested, but also to the way in which the emotions are assessed and measured.

Self-reports

Measures of the effects of an emotion can be generally categorised as objective (behavioural, physiological) or subjective (self-reports). The latter, in the form of quantitative questionnaires, are the most common in eyewitness testimony research. They are used primarily due to convenience, arising from the ease and speed of collecting data and the lack of additional costs. However, as is often pointed out (e.g. Amodio, Zinner & Harmon-Jones 2007 ; Scherer, 2005 ), the use of self-reports carries the risk of getting unreliable statements about the individual’s experience. Subjects may not only be unaware of their emotions, but could also intentionally or unintentionally, mislead the researcher as they try to fulfil the internalised expectations of the research.

Another concern about self-reports is related to their structure. The choice between the dimensional versus discrete approach should be reflected in a properly chosen method of assessment. When it comes to the discrete approach, some doubts may arise when the list of labels is short, forcing an individual to choose one of them, even when they are uncertain about their own emotions. For instance, Yuille and Cutshall ( 1986 ) asked eyewitnesses of real crime to assess their level of stress on a seven-point scale, and to indicate any negative effects engendered by the incident (nightmares, sleeplessness). While the question of negative consequences may be a useful counterbalance for self-reports, limiting the questionnaire to one scale may have resulted in discovering artifacts. When subjects have only one option, they feel obliged to report anything, even if they perceive the event differently than assumed by the researcher.

Thus, it is postulated, any research in eyewitness testimony which assumes a priori that the results of stimulation are negative should also give subjects sufficient options to assess a wider spectrum of emotions, positive included. The experimental situation itself can be seen as novel and interesting, and some subjects in contact with unpleasant stimuli may react with a mixture of excitement and curiosity.

Still on the issue of scale, concerns about the psychometric properties of Likert-type scales depending on rating format are also worth noting. As there is no room here for a detailed discussion, readers seeking a more advanced overview are directed to other papers focused on the issue (e.g.: Cummins & Gullone, 2000 ; Finstad, 2010 ; Leung, 2011 ; Weijters, Cabooter & Schillewaert, 2010 ). However, it should be mentioned that there is substantial evidence showing that, as the internal structure of the scale does not lose its properties regardless of the number of points, the more points a scale has, the more skewness and kurtosis is reduced. Therefore, it is often suggested not only to abandon five-point scales, but even to use 11-points scales that increase sensitivity and follow the normal distribution.

In light of this, methodological considerations may be formulated in relation to studies that rely on scales with a small point range. Hypothetically, when a four-point scale is used (e.g. Houston, Clifford, Phillips & Memon, 2013 ), lacking a neutral point, skewness is expected. Thus, abnormal data distribution is highly probable. Consequently, when our objective is to examine if there are differences in the assessment of emotions between conditions, we should not use parametric estimation tests unless our sample size is big enough to be resistant to non-normality. The T test, for instance, is invalid with small samples from non-normal distributions, and by using it we risk falsely rejecting the null hypothesis. On the other hand, non-parametric tests are underpowered to detect an effect, so they increase the risk of accepting a false null hypothesis (Conover, 1998 ).

Moreover, it is postulated to include the measurement of chronical affective states in research plan. As mentioned, moods can influence the formulation of testimony and, due to mood-congruency effect, enhance the impact of experimental manipulation. Thus, controlling for that variable will help us estimate the interactions between emotions and moods, as well as eliminate the disruptive impact of opposite mood on stimulus manipulation. Questionnaires that allow diagnosis of dispositional mood, affective style or mood disorder are also recommended, as they can be help controlling for individual differences.

Psychophysiology

Another way to assess emotions uses objective measurements of physiological correlates of affective states. Emotions are accompanied by physiological arousal, which reflects the activation of the autonomic nervous system. The most common ways to measure it are to examine changes in electrodermal (EDA/GSR), cardiovascular and respiratory activity. Each has multiple indexes, which are evidence of ANS activation and allow the conclusion that a subject is experiencing not only general arousal, but even emotions. As Kreibig’s ( 2010 ) review shows, there is convincing evidence of emotion-specific ANS activity. Thus, when adopting more than just one method to investigate autonomic response patterns, it may be useful to discuss not only the dimension of core properties of emotional experience, but also the type of discrete emotion. However, it is crucial to note that consideration of only one index is insufficient to indicate what kind of emotion is experienced. Moreover, individual differences in ANS activation should be always taken into account.

Taking into consideration the shortcomings of self-reporting, as well as the nature of emotions and their dimensions that allow us to objectively measure some aspects of emotional experience, it is postulated that, in the case of research on how emotional events are remembered, a heterophenomenological approach should be adopted. This indicates both subjective (self-reports) and objective (psychophysiological) assessment of investigated variables, which may allow us to address discrepancies in previous research. When psychophysiological measurements are included, this may provide us with information on the nature of emotional engagement, demonstrating the effectiveness of experimental manipulation. Thus, it may also serve as an additional manipulation check. On the other hand, using self-reports gives us insight into subjective experiences, personal appraisals and assessments.

The purpose of this paper is to present the theoretical and methodological shortcomings of research into the relationship between emotions and eyewitness testimony. In light of contradicting results, it is crucial to indicate those areas of research that may be responsible for misrepresentation of memory performance.

The summary of the discussion on emotions and their impact on testimony constitutes a proposition of a framework that would allow better comparisons between studies and explanations of conflicting results, while structuring knowledge that will eventually provide a complete theory of the influence of emotions on eyewitness testimony. The framework consists of the following steps:

Defining emotions and applying an approach to study them

Even though there are no reasons to consider the discrete approach as theoretically unsound, the advantage of the dimensional model of emotions is primarily due to the methodological consequences it imposes. When both valence and arousal are considered, the researcher is advised to apply two different methods of measurement—self-reports with a multi-point Likert-like scale to assess valence, and psychophysiological measurement to study arousal. Although there are self-report methods to measure the intensity of emotional experience (e.g. Geneva Emotion Wheel Footnote 3 ), it is crucial to note that, while intensity rating may correlate to arousal, it is not the same. Thus, other methods are required to measure arousal.

Inducing and manipulating emotions

To draw inferences about the impact of emotions on eyewitness testimony, it is crucial to develop an effective experimental manipulation procedure. Emotions are not induced simply because subjects are shown a crime event on video. Watching staged, fictional criminal activity is part of everyday life in our modern world. To simulate real eyewitness experience, the researcher must create conditions that increase the subject’s personal involvement. This is possible if the stimulus has meaning, absorbs attention and seems real. Thus, the best methods to induce emotions are (1) staging crimes, (2) playing virtual reality scenarios, and (3) presenting films capable of evoking transportation into the narrative effect.

A proper memory test

Even though emotions are the main interest of this paper, a model framework for research must also include guidelines on how to examine witnesses' memory. Empirical findings suggest that the influence of emotions depends on memory function. Thus, model research should consider applying more than one way of testing memory performance. Moreover, ecologically valid memory tests reflect what is asked from a real eyewitness. Therefore, it is advised to simulate police procedures for interviewing eyewitnesses, such as (1) free recollection, which may allow us to answer the general question on quantity of details remembered, forgotten or distorted, (2) structured recollection, which may allow us to distinguish between central and peripheral details and how they are remembered, and (3) adequate eyewitness identification procedure, which allows us to investigate if emotions can influence recognition, based on quasi-automatic information processing.

Control for individual differences

Besides the main guidelines considering defining, evoking and measuring emotions, as well as memory testing, it is also advised to control for variables that may explain individual differences in regulating emotions and moods, for example personality traits or affective styles.

To sum up, this paper encourages more strictly empirical studies that ensure theoretical and ecological validity, so the research better represents eyewitness experience and can serve as its parallel. This includes (1) exploiting the legacy of the psychology of emotion and its rich theoretical background for more consistent and multifaceted research designs, (2) ensuring strong experimental manipulation that simulates the eyewitnesses’ experiences to the extent set by research ethics, and (3) adopting a heterophenomenological approach to measuring emotional experience. Meeting these postulates may help us to formulate a coherent theory on the impact of emotions on eyewitness testimony.

However, as Payne et al. ( 2007 ) demonstrated, stress induced prior to the acquisition stage of memory enhances emotional long-term episodic memories.

with exception of disgust, which seems particularly easy to evoke, almost instantly following the stimulus.

The Geneva Emotion Wheel (Sacharin, Schlegel & Scherer, 2012 ) is in fact a tool that combines the discrete and dimensional approaches. Thus, it is recommended for research into eyewitness testimony. Labelling emotions may be helpful for comparing results and may allow us to better understand the combination of emotions experienced by subjects.

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Głomb, K. How to improve eyewitness testimony research: theoretical and methodological concerns about experiments on the impact of emotions on memory performance. Psychological Research 86 , 1–11 (2022). https://doi.org/10.1007/s00426-021-01488-4

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Chapter 8. Remembering and Judging

8.4 Eyewitness Testimony and Memory Biases

Cara Laney and Elizabeth F. Loftus

Learning Objectives

Describe the kinds of mistakes that eyewitnesses commonly make and some of the ways that this can impede justice.
Explain some of the errors that are common in human memory.
Describe some of the important research that has demonstrated human memory errors and their consequences.

What Is Eyewitness Testimony?

Why Is Eyewitness Testimony an Important Area of Psychological Research?

There is now a wealth of evidence, from research conducted over several decades, suggesting that eyewitness testimony is probably the most persuasive form of evidence presented in court, but in many cases, its accuracy is dubious. There is also evidence that mistaken eyewitness evidence can lead to wrongful conviction—sending people to prison for years or decades, even to death row, for crimes they did not commit. Faulty eyewitness testimony has been implicated in at least 75% of DNA exoneration cases—more than any other cause (Garrett, 2011). In a particularly famous case, a man named Ronald Cotton was identified by a rape victim, Jennifer Thompson, as her rapist, and was found guilty and sentenced to life in prison. After more than 10 years, he was exonerated (and the real rapist identified) based on DNA evidence. For details on this case and other (relatively) lucky individuals whose false convictions were subsequently overturned with DNA evidence, see the Innocence Project website ( http://www.innocenceproject.org/ ).

Misinformation

In an early study of eyewitness memory, undergraduate subjects first watched a slideshow depicting a small red car driving and then hitting a pedestrian (Loftus, Miller, & Burns, 1978). Some subjects were then asked leading questions about what had happened in the slides. For example, subjects were asked, “How fast was the car traveling when it passed the yield sign?” But this question was actually designed to be misleading, because the original slide included a stop sign rather than a yield sign.

This phenomenon is called the misinformation effect , because the misinformation that subjects were exposed to after the event (here in the form of a misleading question) apparently contaminates subjects’ memories of what they witnessed. Hundreds of subsequent studies have demonstrated that memory can be contaminated by erroneous information that people are exposed to after they witness an event (see Frenda, Nichols, & Loftus, 2011; Loftus, 2005). The misinformation in these studies has led people to incorrectly remember everything from small but crucial details of a perpetrator’s appearance to objects as large as a barn that wasn’t there at all.

These studies have demonstrated that young adults (the typical research subjects in psychology) are often susceptible to misinformation, but that children and older adults can be even more susceptible (Bartlett & Memon, 2007; Ceci & Bruck, 1995). In addition, misinformation effects can occur easily, and without any intention to deceive (Allan & Gabbert, 2008). Even slight differences in the wording of a question can lead to misinformation effects. Subjects in one study were more likely to say yes when asked “Did you see the broken headlight?” than when asked “Did you see a broken headlight?” (Loftus, 1975).

Identifying Perpetrators

In most jurisdictions in the United States, lineups are typically conducted with pictures, called photo spreads , rather than with actual people standing behind one-way glass (Wells, Memon, & Penrod, 2006). The eyewitness is given a set of small pictures of perhaps six or eight individuals who are dressed similarly and photographed in similar circumstances. One of these individuals is the police suspect, and the remainder are “ foils ” or “fillers” (people known to be innocent of the particular crime under investigation). If the eyewitness identifies the suspect, then the investigation of that suspect is likely to progress. If a witness identifies a foil or no one, then the police may choose to move their investigation in another direction.

A man stands in a darkened room with his face almost entirely obscured by shadow.

Some factors have been shown to make eyewitness identification errors particularly likely. These include poor vision or viewing conditions during the crime, particularly stressful witnessing experiences, too little time to view the perpetrator or perpetrators, too much delay between witnessing and identifying, and being asked to identify a perpetrator from a race other than one’s own (Bornstein, Deffenbacher, Penrod, & McGorty, 2012; Brigham, Bennett, Meissner, & Mitchell, 2007; Burton, Wilson, Cowan, & Bruce, 1999; Deffenbacher, Bornstein, Penrod, & McGorty, 2004).

It is hard for the legal system to do much about most of these problems. But there are some things that the justice system can do to help lineup identifications “go right.” For example, investigators can put together high-quality, fair lineups. A fair lineup is one in which the suspect and each of the foils is equally likely to be chosen by someone who has read an eyewitness description of the perpetrator but who did not actually witness the crime (Brigham, Ready, & Spier, 1990). This means that no one in the lineup should “stick out,” and that everyone should match the description given by the eyewitness. Other important recommendations that have come out of this research include better ways to conduct lineups, “double blind” lineups, unbiased instructions for witnesses, and conducting lineups in a sequential fashion (see Technical Working Group for Eyewitness Evidence, 1999; Wells et al., 1998; Wells & Olson, 2003).

Kinds of Memory Biases

Other sorts of memory biases are more complicated and longer lasting. For example, it turns out that our expectations and beliefs about how the world works can have huge influences on our memories. Because many aspects of our everyday lives are full of redundancies, our memory systems take advantage of the recurring patterns by forming and using schemata , or memory templates (Alba & Hasher, 1983; Brewer & Treyens, 1981). Thus, we know to expect that a library will have shelves and tables and librarians, and so we don’t have to spend energy noticing these at the time. The result of this lack of attention, however, is that one is likely to remember schema-consistent information (such as tables), and to remember them in a rather generic way, whether or not they were actually present.

False Memory

Some memory errors are so “large” that they almost belong in a class of their own: false memories . Back in the early 1990s a pattern emerged whereby people would go into therapy for depression and other everyday problems, but over the course of the therapy develop memories for violent and horrible victimhood (Loftus & Ketcham, 1994). These patients’ therapists claimed that the patients were recovering genuine memories of real childhood abuse, buried deep in their minds for years or even decades. But some experimental psychologists believed that the memories were instead likely to be false—created in therapy. These researchers then set out to see whether it would indeed be possible for wholly false memories to be created by procedures similar to those used in these patients’ therapy.

The problems with memory in the legal system are real. But what can we do to start to fix them? A number of specific recommendations have already been made, and many of these are in the process of being implemented (e.g., Steblay & Loftus, 2012; Technical Working Group for Eyewitness Evidence, 1999; Wells et al., 1998). Some of these recommendations are aimed at specific legal procedures, including when and how witnesses should be interviewed, and how lineups should be constructed and conducted. Other recommendations call for appropriate education (often in the form of expert witness testimony) to be provided to jury members and others tasked with assessing eyewitness memory. Eyewitness testimony can be of great value to the legal system, but decades of research now argues that this testimony is often given far more weight than its accuracy justifies.

Outside Resources

Video 1: Eureka Foong’s – The Misinformation Effect. This is a student-made video illustrating this phenomenon of altered memory. It was one of the winning entries in the 2014 Noba Student Video Award.

Video 2: Ang Rui Xia & Ong Jun Hao’s – The Misinformation Effect. Another student-made video exploring the misinformation effect. Also an award winner from 2014.

Discussion Questions

Imagine that you are a juror in a murder case where an eyewitness testifies. In what ways might your knowledge of memory errors affect your use of this testimony?
How true to life do you think television shows such as CSI or Law & Order are in their portrayals of eyewitnesses?
Many jurisdictions in the United States use “show-ups,” where an eyewitness is brought to a suspect (who may be standing on the street or in handcuffs in the back of a police car) and asked, “Is this the perpetrator?” Is this a good or bad idea, from a psychological perspective? Why?

Image Attributions

Figure 8.21: Robert Couse-Baker, https://goo.gl/OiPUmz, CC BY 2.0, https://goo.gl/BRvSA7

Figure 8.24: Dan Kleinman, https://goo.gl/07xyDD, CC BY 2.0, https://goo.gl/BRvSA7

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Introduction to Psychology Copyright © 2019 by Cara Laney and Elizabeth F. Loftus is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Eyewitness Memory

Our research in this area has focused on several important factors that influence both the recall of information by witnesses and the likelihood of subsequent identification of the perpetrator from a photographic lineup. We approach each of these issues using both basic research and more applied eyewitness paradigms, with the intent of generalizing basic theories of memory to understand factors that influence witness performance.

Improving Eyewitness Recall & Lineup Identification

Research suggests that erroneous eyewitness identification is the primary factor underlying wrongful conviction in the United States. Our research has sought to identify procedures that might alleviate the likelihood of misidentification and to understand the cognitive and social psychological processes that govern misidentification and false memories. We have also worked to identify more diagnostic methods for interviewing witness.

Colloff, M. F., Flowe, H. D., Smith, H. M. J., Seale-Carlisle, T. M., Meissner, C. A., Rockey, J. C., Pande, B., Kujur, P., Parveen, N., Chandel, P., Singh, M. M., Pradhan, S., & Parganiha, A. (2022). Active exploration of faces in police lineups increases discrimination accuracy. American Psychologist , 77 , 196-220.

Dianiska, R. E., Manley, K. D., & Meissner, C. A. (2021) . A process perspective: The importance of theory in eyewitness identification research. In Smith et al. (Eds.), Methods, measures, and theories in eyewitness identification tasks . Taylor & Francis.

Wells, G. L., Kovera, M. B., Douglass, A. B., Brewer, N., Meissner, C. A., & Wixted, J. T. (2020) . Policy and procedure recommendations for the collection and preservation of eyewitness evidence. Law & Human Behavior, 44, 3-36.

Jones, R. L., Scullin, M. H, & Meissner, C. A. (2011) . Evidence of differential performance on simultaneous and sequential lineups for individuals with autism-spectrum traits. Personality & Individual Differences , 51 , 537-540.

Malpass, R. S., Ross, S. J., Meissner, C. A., & Marcon, J. L. (2009) . The need for expert psychological testimony on eyewitness identification. In B. Cutler’s (Ed.), E xpert testimony on the psychology of eyewitness identification (pp. 3-27). Kluwer Academic/Plenum Press.

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Haw, R. M., Dickinson, J. J., & Meissner, C. A. (2007) . The phenomenology of carryover effects between showup and lineup identification. Memory , 15 , 117-127.

Bornstein, B. H., & Meissner, C. A. (2008) . Basic and applied issues in eyewitness research: A Münsterberg centennial retrospective. Applied Cognitive Psychology , 22 , 733-736.

Malpass, R. S., Susa, K. J., & Meissner, C. A. (2008) . Training of eyewitnesses. In B. Cutler’s (Ed.), Encyclopedia of psychology & law, Vol. 2 (pp. 807-808). Sage Publications.

Susa, K. J., & Meissner, C. A. (2008) . Accuracy of eyewitness descriptions. In B. Cutler’s (Ed.), Encyclopedia of psychology & law, Vol. 1 (pp. 285-287). Sage Publications.

Malpass, R. S., Zimmerman, L. A., Meissner, C. A., Ross, S. J., Rigoni, M. E., Topp, L. D., Pruss, N., Tredoux, C. T., & Leyva, J. M. (2005) . Eyewitness memory and identification. The San Antonio Defender , 7 , 2-13.

Meissner, C. A., Tredoux, C. G., Parker, J. F., & MacLin, O. H. (2005) . Eyewitness decisions in simultaneous and sequential lineups: A dual-process signal detection theory analysis. Memory & Cognition , 33 , 783-792.

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Cross-Racial Identification

Faces of one’s own race are better remembered when compared with faces of another, less familiar race. This phenomenon is often referred to as the “cross-race effect” or “own-race bias,” and has been demonstrated across a variety of memory tasks (e.g., recognition, identification, forced choice, etc.), in both adults and children and across a variety of ethnic groups (e.g., White, Black, Hispanic, Asian, etc.). We have recently extended our understanding of this phenomenon to perceptual identification paradigms (simulating the task of a TSA agent).

Susa, K. J., Dessenberger, S. J., Michael, S. W., & Meissner, C. A. (2019) . Imposter identification in low prevalence environments. Legal & Criminological Psychology, 24 , 179-193.

Bornstein, B. H., Laub, C. E., Meissner, C. A., Susa, K. J. (2013) . The cross-race effect: Resistant to instructions. Journal of Criminology , 1-6.

Meissner, C. A., Susa, K. J., & Ross, A. B. (2013) . Can I see your passport please? Perceptual discrimination of own- and other-race faces. Visual Cognition , 21 , 1287-1305.

Marcon, J. L., Meissner, C. A., Freuh, M., Susa, K. J., & MacLin, O. H. (2010) . Perceptual identification and the cross-race effect. Visual Cognition , 18 , 767-779.

Susa, K. J., Meissner, C. A., & de Heer, H. (2010) . Modeling the role of social-cognitive processes in the recognition of own- and other-race faces. Social Cognition , 28 , 519-533.

Evans, J. R., Marcon, J. L., & Meissner, C. A. (2009) . Cross-racial lineup identification: The potential benefits of context reinstatement. Psychology, Crime, & Law , 15 , 19-28.

Marcon, J. L., Susa, K. J., & Meissner, C. A. (2009). Assessing the influence of recollection and familiarity in memory for own- and other-race faces. Psychonomic Bulletin & Review , 16 , 99-103 .

Chiroro, P. M., Tredoux, C. G., Radaelli, S., & Meissner, C. A. (2008) . Recognizing faces across continents: The effect of within-race variations on the own-race bias in face recognition. Psychonomic Bulletin & Review , 15 , 1089-1092.

Jackiw, L. B., Arbuthnott, K. D., Pfeifer, J. E., Marcon, J. L., & Meissner, C. A. (2008) . Examining the cross-race effect in lineup identification using Caucasian and First Nations samples. Canadian Journal of Behavioural Science , 40 , 52-57.

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Brigham, J. C., Bennett, L. B., Meissner, C. A., & Mitchell, T. L. (2007) . The influence of race on eyewitness memory. In R. Lindsay, D. Ross, J. Read, & M. Toglia, (Eds). Handbook of eyewitness psychology: Memory for people (pp. 257-281), Lawrence Erlbaum & Associates.

Corenblum, B., & Meissner, C. A. (2006) . Recognition of faces of ingroup and outgroup children and adults. Journal of Experimental Child Psychology , 93 , 187-206.

Meissner, C. A., Brigham, J. C., & Butz, D. A. (2005) . Memory for own- and other-race faces: A dual-process approach. Applied Cognitive Psychology , 19 , 545-567.

Meissner, C. A., & Brigham, J. C. (2001) . Thirty years of investigating the own-race bias in memory for faces: A meta-analytic review. Psychology, Public Policy, & Law , 7 , 3-35.

Slone, A. E., Brigham, J. C., & Meissner, C. A. (2000) . Social and cognitive factors affecting the own-race bias in Whites. Basic & Applied Social Psychology , 22 , 71-84.

The Description-Identification Relationship & “Verbal Overshadowing”

An individuals’ ability to describe a face does not always relate to their ability to identify a face. Similarly, the processes that govern face descriptions vs. identification appear distinct. Our research has continued to examine this description-identification relationship through the “verbal overshadowing” effect — the finding that describing a face via verbal description can subsequently impair identification of that face from a lineup.

Alonga et al. (2014) . Registered replication report: Schooler and Engstler-Schooler (1990). Perspectives on Psychological Science , 9 , 556-578.

Meissner, C. A., Sporer, S. L., & Susa, K. J. (2008) . A theoretical and meta-analytic review of the relationship between verbal descriptions and identification accuracy in memory for faces. European Journal of Cognitive Psychology , 20 , 414-455.

Meissner, C. A., Sporer, S. L., & Schooler, J. W. (2007) . Person descriptions as eyewitness evidence. In R. Lindsay, D. Ross, J. Read, & M. Toglia, (Eds). Handbook of eyewitness psychology: Memory for people (pp. 3-34), Lawrence Erlbaum & Associates.

Meissner, C. A. (2002) . Applied aspects of the instructional bias effect in verbal overshadowing. Applied Cognitive Psychology , 16 , 911-928.

Meissner, C. A., & Memon, A. (2002) . Verbal overshadowing: A special issue exploring theoretical and applied issues. Applied Cognitive Psychology , 16 , 869-872.

Meissner, C. A., & Brigham, J. C. (2001) . A meta-analysis of the verbal overshadowing effect in face identification. Applied Cognitive Psychology , 15 , 603-616.

Meissner, C. A., Brigham, J. C., & Kelley, C. M. (2001) . The influence of retrieval processes in verbal overshadowing. Memory & Cognition , 29 , 176-186.

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PDF Eyewitness Memory: How Stress and Situational Factors Affect Eyewitness
of these factors affects eyewitness memory. One common way to examine the. ionship between stress and fear is to examine changes. in memory performance asthe severi. gerous the crime is, the monetary worth of objects that are stolen or dam. or the personal stake one has in the crime (Narby, Cutler & Penrod 1996).
Eyewitness Testimony in Psychology
Eyewitness testimony is an important area of research in cognitive psychology and human memory. Juries tend to pay close attention to eyewitness testimony and generally find it a reliable source of information. However, research into this area has found that eyewitness testimony can be affected by many psychological factors:
Eyewitness testimony
Summary. The study of eyewitness testimony is thriving. Over the last three decades, psychologists have made important discoveries, and applied those discoveries to the legal system in myriad ways. Along the way, there were disagreements, which were typically healthy in nature. I discuss a few, for example, centering around the impact of ...
PDF A PRIMER ON THE PSYCHOLOGY OF EYEWITNESS MEMORY
accurate and inaccurate eyewitness decisions. The goal of this Essay is to attempt to provide answers to these important issues from a scientific (psychological) perspective. Over the last several decades, eyewitness researchers have learned a tremendous amount about the causes of mistaken identifications and other eyewitness errors.
Rethinking the Reliability of Eyewitness Memory
The rest of the entry is written as if to validate Justice Brennan's decades-old impression of eyewitness memory. Third, many psychology textbooks convey the message that eyewitness memory is unreliable, as readers can easily confirm for themselves if there is an introductory psychology text (or, perhaps, a social psychology text or memory ...
Eyewitness Memory
In the early days of modern psychology, German-American applied psychologist Hugo Munsterberg published On the Witness Stand (Munsterberg 1908), in which he described eyewitness memory errors as fully possible, not always indicated by confidence in one's memory, and undistinguishable by the legal system from accurate memories.Munsterberg was ahead of his time, and the field of psychology did ...
Eyewitness Memory
Eyewitness identification procedures are tests of face recognition memory. There are several different ways to conduct such tests, but the common denominator of all of them is that they involve a suspect, who is the person the police think may have committed the crime and who is either innocent or guilty.
PDF The new science of eyewitness memory
Signal detection theory, coupled with ROC analysis and confidence calibration, is pointing toward a new science of eyewitness memory. The new science shifts the blame for faulty testimony from unreliable eyewitnesses to other actors in the law enforcement and legal community actors whose behaviors can —.
How to improve eyewitness testimony research: theoretical and
There is hardly a textbook on the psychology of eyewitness testimony that suggests otherwise. ... Readers interested in more general knowledge on the application of eyewitness testimony research may refer to other papers available in the literature (e ... Methodological issues in the study of eyewitness memory and arousal. Creighton L. Rev ...
Eyewitness Memory Is a Lot More Reliable Than You Think
This article was originally published with the title " Eyewitness Memory Is a Lot More Reliable Than You Think " in SA Mind Vol. 28 No. 6 (November 2017), p. 35 doi:10.1038 ...
Evaluating witness testimony: Juror knowledge, false memory, and the
In one telephone survey participated in by 1838 people in the USA, 37.1% of respondents mostly agreed or strongly agreed that 'In my opinion, the testimony of one confident eyewitness should be enough evidence to convict a defendant of a crime', 63% of respondents mostly agreed or strongly agreed that 'Human memory works like a video ...
Understanding eyewitness memory: Theory and applications.
This book reviews a number of important topics from basic research on perception and memory with respect to key findings and theories and relates this knowledge to what is known from eyewitness memory research. It also discusses the implications of these findings for the theoretical understanding of eyewitness memory and for potential applications that could help improve the quality and ...
The effects of stress on eyewitness memory: A survey of memory experts
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 ...
Eyewitness Testimony and Memory Construction
Eyewitness Misidentification. Even though memory and the process of reconstruction can be fragile, police officers, prosecutors, and the courts often rely on eyewitness identification and testimony in the prosecution of criminals. However, faulty eyewitness identification and testimony can lead to wrongful convictions (Figure 1).
Rethinking the Reliability of Eyewitness Memory
Evidence supporting the idea that eyewitness memory is widely perceived to be inherently unreliable is abun-dant. First, a search of Google using the exact phrase "eyewitness memory is unreliable" yielded 2,250 hits.1 By contrast, a search of the exact phrase "eyewitness memory is reliable" yielded only 2 hits.
Eyewitness Testimony and Memory Biases
21. Eyewitness Testimony and Memory Biases. Eyewitnesses can provide very compelling legal testimony, but rather than recording experiences flawlessly, their memories are susceptible to a variety of errors and biases. They (like the rest of us) can make errors in remembering specific details and can even remember whole events that did not ...
The Handbook of Eyewitness Psychology: Volume I
The Handbook of Eyewitness Psychology presents a survey of research and legal opinions from international experts on the rapidly expanding scientific literature addressing the accuracy and limitations of eyewitnesses as a source of evidence for the courts.For the first time, extensive reviews of factors influencing witnesses of all ages-children, adults, and the elderly-are compiled in a ...
Eyewitness Imagination: How Our Minds Change Our Memories
Recognition and Reconfiguration: Demand-Based Confabulation in Initial Eyewitness Memory. Journal of Investigative Psychology and Offender Profiling, 9, 149-160. SHARE
How to improve eyewitness testimony research: theoretical and
The purpose of this paper is to present crucial shortcomings of research into eyewitness testimony. It presents the state-of-the-art of research on the relationship between emotions and memory performance. In addition, it addresses contradictions and concerns about previous studies. Despite the declarations of consensus on the role of emotions in memory coding and retrieving, there are as many ...
8.4 Eyewitness Testimony and Memory Biases
Cara Laney and Elizabeth F. Loftus. Eyewitnesses can provide very compelling legal testimony, but rather than recording experiences flawlessly, their memories are susceptible to a variety of errors and biases. They (like the rest of us) can make errors in remembering specific details and can even remember whole events that did not actually happen.
Eyewitness Memory
Eyewitness Memory. Our research in this area has focused on several important factors that influence both the recall of information by witnesses and the likelihood of subsequent identification of the perpetrator from a photographic lineup. We approach each of these issues using both basic research and more applied eyewitness paradigms, with the ...
Eyewitness Testimony Essay
Accuracy and Memory of Eyewitness Testimony James B. Driscoll Grand Canyon University: PSY 102 12/15/ Eyewitness Testimony Eyewitness misidentifications made with high confidence from eyewitness testimony and memory in a court of law under oath have been known to have played a role in more than 70%- 75% of the 358 wrongful convictions that have been overturned based on DNA evidence since 1989 ...

Eyewitness Testimony in Psychology

Anxiety / Stress

Reconstructive Memory

Weapon Focus

Article contents

A Brief Tutorial on How Memory Works

Testing Recall of Events Using an Interview

Memory Is Malleable

Moral Panics Involving Apparently False Memories

The McMartin Preschool Trial

Recovered Memories of Childhood Sexual Abuse

Structured Interviews

Other Sources of Memory Contamination

Even Recollections of Salient Events Become Less Reliable Over Time

Reminiscence

Testing Face Recognition Using a Photo Lineup

Conducting a Proper Lineup Procedure

Lineups Increase Discriminability

Maximizing Information

Test a Witness’s Memory for a Suspect Only Once

Disregard the Witness’s Explanation for Why a Face Recognition Decision Changed

Under the Right Conditions, Eyewitness Memory Is Highly Reliable

Further Reading

Related Articles

Eyewitness Memory Is a Lot More Reliable Than You Think

On supporting science journalism

The effects of stress on eyewitness memory: A survey of memory experts and laypeople

Henry Otgaar

Melanie Sauerland

Supplementary Information

Stress and memory: An ongoing discussion

The current survey

Participants

Exclusion criteria

Layperson and expert statements

Additional expert statements and questions

Data analyses

Comparison with past work

Eyewitness experts versus fundamental memory experts

Laypeople versus experts

Expert beliefs about moderators between encoding stress and memory

Expert beliefs about moderators between retrieval stress and memory

Expert beliefs on neuroscientific statements

Layperson beliefs about stress effects on memory

Implications for applied legal settings

Limitations and future directions

Author note

Funding information

Eyewitness Testimony and Memory Construction

Memory Construction and Reconstruction

Eyewitness Misidentification

Link to Learning

Dig Deeper: Preserving Eyewitness Memory: The Elizabeth Smart Case

Elizabeth Loftus and the Misinformation Effect

Controversies over Repressed and Recovered Memories

More on False Memories

Think It Over

21 Eyewitness Testimony and Memory Biases

What is Eyewitness Testimony?

Why Is Eyewitness Testimony an Important Area of Psychological Research?

Misinformation

Identifying Perpetrators

Kinds of Memory Biases

False Memory

Text Attribution

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TABLE OF CONTENTS

Eyewitness Imagination: How Our Minds Change Our Memories

How to improve eyewitness testimony research: theoretical and methodological concerns about experiments on the impact of emotions on memory performance

Cite this article

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The Effects of emotion on judgments of learning and memory: a meta-analytic review

Examining Memory in the Context of Emotion and Motivation

Emotional oddball: A review on memory effects

Introduction

What do we know about emotions and eyewitness testimony?

How eyewitness testimony research goes astray

Defining emotions

Negative emotion