Are multiple-trial experiments appropriate for eyewitness identification studies? Accuracy,choosing, and confidence across trials

Eyewitness identification experiments typically involve a single trial: A participant views an event and subsequently makes a lineup decision. As compared to this single-trial paradigm, multiple-trial designs are more efficient, but significantly reduce ecological validity and may affect the strategies that participants use to make lineup decisions. We examined the effects of a number of forensically relevant variables (i.e., memory strength, type of disguise, degree of disguise, and lineup type) on eyewitness accuracy, choosing, and confidence across 12 target-present and 12 target-absent lineup trials (N?=?349; 8,376 lineup decisions). The rates of correct rejections and choosing (across both target-present and target-absent lineups) did not vary across the 24 trials, as reflected by main effects or interactions with trial number. Trial number had a significant but trivial quadratic effect on correct identifications (OR?=?0.99) and interacted significantly, but again trivially, with disguise type (OR?=?1.00). Trial number did not significantly influence participants’ confidence in correct identifications, confidence in correct rejections, or confidence in target-absent selections. Thus, multiple-trial designs appear to have minimal effects on eyewitness accuracy, choosing, and confidence. Researchers should thus consider using multiple-trial designs for conducting eyewitness identification experiments.     

Effects of postidentification feedback on eyewitness identification and nonidentification confidence

Two experiments investigated new dimensions of the effect of confirming feedback on eyewitness identification confidence using target-absent and target-present lineups and (previously unused) unbiased witness instructions (i.e., "offender not present" option highlighted). In Experiment 1, participants viewed a crime video and were later asked to try to identify the thief from an 8-person target-absent photo array. Feedback inflated witness confidence for both mistaken identifications and correct lineup rejections. With target-present lineups in Experiment 2, feedback inflated confidence for correct and mistaken identifications and lineup rejections. Although feedback had no influence on the confidence-accuracy correlation, it produced clear overconfidence. Confidence inflation varied with the confidence measure reference point (i.e., retrospective vs. current confidence) and identification response latency.     

The effect of viewing distance on empirical discriminability and the confidence–accuracy relationship for eyewitness identification

The distance from which an eyewitness views a perpetrator is a critical factor for eyewitness identification, but has received little research attention. We presented three mock-crime videos to participants, varying distance to three perpetrators (3, 10, or 20 m). Across two experiments, increased distance reduced empirical discriminability in the form of a mirror effect, such that correct identifications decreased while false identifications increased. Moreover, high confidence identifications were associated with high accuracy at 3 m (Experiment 1 and 2) and 10 m (Experiment 2), but not at 20 m. We conclude that eyewitnesses may be less likely to identify a perpetrator viewed at a distance, and also more likely to falsely identify an innocent suspect. Furthermore, there may be certain boundary conditions associated with distance and the impact it has on the confidence–accuracy relationship. More research is needed to elucidate the effect of estimator variable manipulations on the confidence–accuracy relationship.     

Biased lineup instructions and face identification from video images

Previous eyewitness memory research has shown that biased lineup instructions reduce identification accuracy, primarily by increasing false-positive identifications in target-absent lineups. Because some attempts at identification do not rely on a witness's memory of the perpetrator but instead involve matching photos to images on surveillance video, the authors investigated the effects of biased instructions on identification accuracy in a matching task. In Experiment 1, biased instructions did not affect the overall accuracy of participants who used video images as an identification aid, but nearly all correct decisions occurred with target-present photo spreads. Both biased and unbiased instructions resulted in high false-positive rates. In Experiment 2, which focused on video-photo matching accuracy with target-absent photo spreads, unbiased instructions led to more correct responses (i.e., fewer false positives). These findings suggest that investigators should not relax precautions against biased instructions when people attempt to match photos to an unfamiliar person recorded on video.     

The confidence-accuracy relationship in eyewitness identification: the effects of reflection and disconfirmation on correlation and calibration

Participants viewed a simulated crime and attempted an identification from an 8-person target-present or target-absent lineup. The authors examined identification confidence-accuracy relations, contrasting a control condition (n = 310) with 2 manipulations designed to improve confidence scaling. Before indicating confidence, participants reflected on encoding and identification test conditions (n = 316) or suggested hypotheses about why their identification decision might have been wrong (n = 318). Confidence-accuracy correlations were weak and did not differ across conditions. However, for positive identifications, confidence and accuracy were well calibrated in the experimental conditions, although not in the control condition; similar patterns were observed for lineup rejections. Explanations for calibration differences in terms of discrimination difficulty, (mis)match between encoding and test stimuli, and the availability of confidence cues were advanced.     

The Influence of Perpetrator Exposure Time and Weapon Presence/Timing on Eyewitness Confidence and Accuracy

Crimes can occur in a matter of seconds, with little time available for an eyewitness to encode a perpetrator's face. The presence of a weapon can further exacerbate this situation. Few studies have featured mock crimes of short duration, especially with a weapon manipulation. We conducted an experiment to investigate the impact of weapon presence and short perpetrator exposure times (3 vs. 10 seconds) on eyewitness confidence and accuracy. We found that recall concerning the perpetrator was worse when a weapon was present, replicating the weapon focus effect. However, there was no effect on eyewitness identification accuracy. Calibration analyses revealed that all conditions produced a strong confidence–accuracy relationship. Confidence–accuracy characteristic curves illustrated almost perfect accuracy for suspect identifications at the highest levels of confidence. We conclude that weapon presence during a brief crime does not necessarily result in negative consequences for either eyewitness identification accuracy or the confidence–accuracy relationship. Copyright © 2016 John Wiley & Sons, Ltd.     

Children's metacognitive judgments in an eyewitness identification task

Two experiments examined children's metacognitive monitoring of recognition judgments within an eyewitness identification paradigm. A confidence-accuracy (CA) calibration approach was used to examine patterns of calibration, over-/underconfidence, and resolution. In Experiment 1, children (n=619, mean age=11 years 10 months) and adults (n=600) viewed a simulated crime and attempted two separate identifications from 8-person target-present or target-absent lineups given lineup instructions that manipulated witnesses choosing patterns by varying the degree of social pressure. For choosers, but not nonchoosers, meaningful CA relations were observed for adults but not for children. Experiment 2 tested a guided hypothesis disconfirmation manipulation designed to improve the realism of children's metacognitive judgments. Children (N=796, mean age=11 years 11 months) in experimental and control conditions viewed a crime and attempted two separate identifications. The manipulation had minimal impact on the CA relation for choosers and nonchoosers. In contrast to adults, children's identification confidence provides no useful guide for investigators about the likely guilt or innocence of a suspect. These experiments revealed limitations in children's metacognitive monitoring processes that have not been apparent in previous research on recall and recognition with younger children.     

The phenomenology of carryover effects between show-up and line-up identification

This study explored carryover effects from show-ups to subsequent line-up identifications using a novel paradigm in which participants rendered multiple identification judgements. A total of 160 participants studied a series of faces and subsequently viewed a series of target-absent and target-present show-ups. Following a retention interval, participants then made identification judgements from a series of target-absent and target-present line-ups. Remember-Know-Guess judgements were collected to assess the phenomenological basis of carryover effects in face identification. Our results indicated clear carryover effects from show-ups to line-ups, such that repeated exposure to a face increased the likelihood that it would later be identified, regardless of whether or not it had been presented at the time of study. The phenomenological basis for these carryover effects is discussed, as are the implications of these findings for police conduct of multiple eyewitness identification procedures.     

Multiple confidence estimates as indices of eyewitness memory

Eyewitness identification decisions are vulnerable to various influences on witnesses' decision criteria that contribute to false identifications of innocent suspects and failures to choose perpetrators. An alternative procedure using confidence estimates to assess the degree of match between novel and previously viewed faces was investigated. Classification algorithms were applied to participants' confidence data to determine when a confidence value or pattern of confidence values indicated a positive response. Experiment 1 compared confidence group classification accuracy with a binary decision control group's accuracy on a standard old-new face recognition task and found superior accuracy for the confidence group for target-absent trials but not for target-present trials. Experiment 2 used a face mini-lineup task and found reduced target-present accuracy offset by large gains in target-absent accuracy. Using a standard lineup paradigm, Experiments 3 and 4 also found improved classification accuracy for target-absent lineups and, with a more sophisticated algorithm, for target-present lineups. This demonstrates the accessibility of evidence for recognition memory decisions and points to a more sensitive index of memory quality than is afforded by binary decisions.     

Attempts to Improve Children's Identifications From Sequential-Presentation Lineups

The effectiveness of practice and stringent lineup instructions in improving children's identifications from sequential-presentation lineups was investigated. Elementary school children ( N = 144) viewed a slide sequence of a crime followed by practice or control procedures. In the practice conditions, children either practiced themselves (self) or watched a videotape of a child practicing (modeled). Practice consisted of 2 target-absent lineups (unmixed) or a target-absent lineup and a target-present lineup (mixed) of female photos unrelated to the crime. The control conditions did not engage in identification practice. All witnesses were given stringent instructions for identifying the criminal from target-present or target-absent sequential-presentation lineups. Multiple responding was dramatically reduced. Practice affected gender differentially. Female children increased in correct identifications, whereas male children increased in false rejections. None of the practice procedures reduced foil identifications from target-absent lineups.     

Why Do Eyewitnesses Make So Many Mistakes?

Previous research on eyewitness identification has demonstrated high rates of error. Subjects have frequently identified innocent targets as the "criminal" they had seen earlier (false identifications) or had falsely claimed that the criminal was not in the line-up (misses). The present study examines whether identification error rates are inflated by pressures in the typical experimental situation to "make a guess" regardless of one's confidence in the accuracy of the response. It was found that providing an explicit option for subjects to respond "don't know" significantly decreased false identifications and misses with no cost to the proportion of correct identifications. The addition of written and verbal instructions emphasizing the acceptability of the "don't know" option produced a marginally significant further decline in identification errors, again without cost to correct identifications. The discussion considered implications of the present results for experimental and actual police line-up procedures.     

The Moderating Effect of Ecphoric Experience on Post‐identification Feedback: A Critical Test of the Cues‐based Inference Conceptualization

Confidence inflation from confirming post‐identification feedback is greater when the eyewitness is inaccurate than when the eyewitness is accurate, which is evidence that witnesses infer their confidence from feedback only to the extent that their internal cues are weak. But the accurate/inaccurate asymmetry has alternative interpretations. A critical test between these interpretations was conducted by including disconfirming feedback conditions. Student participants (n = 404) witnessed a mock crime, had either a strong or weak ecphoric experience when making their line‐up identifications, and subsequently received no feedback, confirming feedback, or disconfirming feedback. Consistent with a cues‐based conceptualization of the feedback effect, disconfirming feedback influenced witnesses with weak ecphoric experiences more than witnesses with strong ecphoric experiences, ironically increasing the confidence‐accuracy relation. Copyright © 2011 John Wiley & Sons, Ltd.     

不同列队呈现方式下反馈对目击证人辨认自信心的影响

采用辨认后反馈范式研究不同队列呈现方式下反馈对目击证人辨认自信心的影响。结果发现：（1）所有辨认者中,反馈组被试自信心显著高于控制组被试的自信心;反馈方式与辨认选择的交互作用显著,辨认选择与列队呈现方式的交互作用显著;（2）积极辨认者中,反馈组被试的自信心显著高于控制组被试的自信心;正确辨认被试的自信心显著高于错误辨认被试的自信心。结果表明：目击辨认中存在辨认后反馈效应;积极辨认者中辨认自信心可以作为辨认准确性的一个参考指标。     

Presence of administrators differentially impacts eyewitness discriminability for same- and other-race identifications

Best practice guidelines recommend that eyewitness lineup administrators be blind to a suspect's identity, but no research has investigated whether the mere presence of a lineup administrator impacts eyewitness identification decisions. Informed by social facilitation theory, we predicted that the presence of an audience would differentially impact identification accuracy for same- and other-race identifications. Participants (N = 191) viewed same- and other-race lineups either with an audience or alone. Although the presence of an audience did not directly impact identification accuracy, significant indirect effects indicated that the audience provoked evaluation apprehension which hindered other-race identification accuracy and improved same-race identification accuracy. We suggest that using double-blind lineup procedures may not sufficiently protect eyewitness identification accuracy when making other-race lineup decisions in the presence of others.     

Positive versus negative face recognition decisions: confidence,accuracy, and response latency

A large amount of eyewitness identification and face recognition research has investigated the confidence–accuracy (CA) relationship. One consistent finding is that positive recognition decisions (or choosers) demonstrate superior CA calibration to negative recognition decisions (or non‐choosers). This experiment tested whether an explanation of this difference, based on the information available for confidence judgements, accounted for the pattern of CA calibration in positive and negative face recognition decisions. CA calibration for positive and negative decisions was compared for both item and associative recognition judgements. Significantly greater resolution was observed for positive decisions in both the item and associative conditions. Similarly, for both judgement types, positive decisions evidenced a stronger response latency–accuracy relationship than negative decisions. Implications for diagnosing the accuracy of eyewitness identification are discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Postidentification feedback affects real eyewitnesses

Many studies of simulated eyewitness situations have shown that under certain laboratory conditions, people's confidence about their identifications predicts their accuracy, but that their reported confidence can be affected by telling them that they chose the suspect. In this study, eyewitnesses (n= 134) to real crimes took part in lineups at an identification suite in the United Kingdom and were asked questions about their memory both before and after they were told whether they had identified the suspect or a filler. Before the eyewitnesses were told whether they had identified the suspect or a filler, their responses to several questions reliably differentiated between those who identified the suspect and those who identified a filler. In addition, responses to the memory questions were affected by telling the eyewitnesses whether or not they had identified the suspect. These results show that postidentification feedback affects real eyewitnesses and highlight the importance of recording meta-memory variables before an eyewitness discovers whether he or she has identified the suspect.     

Phenomenological reports diagnose accuracy of eyewitness identification decisions

This study investigated whether measuring the phenomenology of eyewitness identification decisions aids evaluation of their accuracy. Witnesses (N = 502) viewed a simulated crime and attempted to identify two targets from lineups. A divided attention manipulation during encoding reduced the rate of remember (R) correct identifications, but not the rates of R foil identifications or know (K) judgments in the absence of recollection (i.e., K/[1 − R]). Both RK judgments and recollection ratings (a novel measure of graded recollection) distinguished correct from incorrect positive identifications. However, only recollection ratings improved accuracy evaluation after identification confidence was taken into account. These results provide evidence that RK judgments for identification decisions function in a similar way as for recognition decisions; are consistent with the notion of graded recollection; and indicate that measures of phenomenology can enhance the evaluation of identification accuracy.     

The Effect of Mugshot Inspections on Eyewitness Identification Accuracy1

This study assessed the effect of commitment to an earlier mugshot identification on the ability to make a subsequent lineup identification. Shortly after viewing videotape of a staged assault some subjects rated a group of 18 photos for attractiveness, whereas other subjects attempted to identify the assailant publicly or privately in the same (target-absent) set of 18 “mugshot” photos. The remaining subjects had no intervening task. Two days later, all subjects attempted to identify the assailant from a six-person target-present photo lineup which contained their mugshot choice (if made) as well as the original assailant. Lineup identifications were significantly less accurate for subjects who had viewed the intervening mugshots (33% accuracy) than those who had only rated the intervening photos for attractiveness (64% accuracy) or had seen no intervening photos (69% accuracy). When viewing lineups, experimental subjects tended to remain committed to their earlier action of choosing or not choosing anyone from the mugshots. More witnesses who had publicly stated their mugshot choice reproduced their (incorrect) choice at the lineup (78%), than did those who made a private mugshot choice (45%), though this difference was not statistically reliable. Witnesses' confidence in their lineup decision was not significantly related to overall accuracy. Contrary to predictions from self-perception theory, confidence in one's decision decreased significantly as further identifications were attempted.     

Don't it make my brown eyes blue: Co-witness misinformation about a target's appearance can impair target-absent line-up performance

Misinformation from another witness has been shown to impair eyewitness reports, but little is known about how it may influence eyewitness identification. In Experiment 1, adult pairs comprising one participant and one experimental confederate viewed a video clip of a staged theft. Half of the participants were then misinformed by the confederate that the thief's accomplice had blue eyes (in fact, they were brown). Next, individual participants described the accomplice and completed a target-absent photographic line-up task comprising blue-eyed members. Misinformed participants were several times more likely than controls to describe the accomplice as having blue eyes, and twice as likely to identify someone from the line-up. In Experiment 2, when line-up members’ eye colour was digitally altered from blue to brown, the line-up effect disappeared, suggesting that the increase in identifications in Experiment 1 was not a generalised increase in willingness to choose from the line-up. In Experiment 3, we discounted the possibility that discussion alone could account for the line-up misinformation effect, by subjecting all participants to co-witness discussion.