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

Abstract

Eyewitness identification experiments typically involve a single trial: A participant views an event and subsequently makes a lineup decision. As compared to this singletrial 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. Keywords Eyewitness identification . Simultaneous and sequential lineups . Multiple trials . Multilevel modelling . Eyewitness confidenceEyewitness identification research has contributed significantly to judicial and policing practices over the past few decades and this momentum continues (Innocence Project, n.d.; State v. Henderson, 2011; Technical Working Group for Eyewitness Evidence, 1999; National Research Council, 2014). A major challenge to eyewitness researchers is the balance between ecological validity and methodological rigor: Researchers must decide which aspects of their experimental design are critical for internal validity and which ought to closely resemble those encountered by real-world eyewitnesses to ensure external validity. In the real world, eyewitnesses typically see one crime and (may) participate in an identification procedure for a suspect. Translated into an experimental design, a participant is assigned to one experimental condition and views one mock crime and an accompanying lineup. This between-subjects design has the advantage of closely mirroring the real eyewitness experience but the disadvantage of producing only one recognition and one confidence data point per participant (cf. Brewer, Weber, Clark, & Wells, 2008).Researchers obtaining a single data point per participant (per measure) require a large number of participants to obtain sufficient power to detect reliable differences. Concerns about power are heightened when the measure of interest is Electronic supplementary material The online version of this article (doi:10.3758/s13428-017-0855-0) contains suppleme...

Eyewitness identification for multiple perpetrator crimes

“…These results are in line with a recent study that considers the effect of making multiple lineup decisions, although not within the theoretical framework of sequential dependencies (Mansour, Beaudry, & Lindsay, 2017). In that study, participants watched 24 videos, each followed by lineup identification decisions on target-present and target-absent trials.…”

“…If an eyewitness is asked to make multiple identification decisions for multiple suspects, this means they may either make multiple identification decisions in succession, or make multiple identification decisions within the same lineup. In regards to the former, research thus far suggests that making multiple identification decisions is at least not harmful to eyewitness memory (Mansour, Beaudry, & Lindsay, 2017). And indeed, the most important benefit of the single suspect lineup -the reduction in the probability that a suspect will be identified by chance -remains.…”

“…This research was also the first to examine sequential dependencies in the field of eyewitness identification, specifically for multiple perpetrator crimes. However, at the time of writing, there has been one other recent study that considers the effect of making multiple lineup decisions, although not within the theoretical framework of sequential effects (Mansour, Beaudry, & Lindsay, 2017). Mansour and colleagues asked whether multiple-trial experiments are appropriate for eyewitness research; in particular they focused on whether accuracy, choosing, and confidence rates changed over the course of eyewitness trials.…”

Stark Individual Differences: Face Recognition Ability Influences the Relationship Between Confidence and Accuracy in a Recognition Test of Game of Thrones Actors

“…While the majority of people can easily recognize family members and friends in a variety of situations, this task is far more challenging for unfamiliar faces (Kramer, Young, & Burton, 2018). As some examples of this difficulty, growing literature suggests that minimal disguises (such as sunglasses) can impair face recognition accuracy (Mansour, Beaudry, & Lindsay, 2017;Nguyen & Pezdek, 2017;Righi, Peissig, & Tarr, 2012;Terry, 1994). Moreover, studies in the face matching literature (i.e., indicating whether two simultaneously presented faces are the same person or different people), show that subtle changes in viewing conditions (e.g., photos of the same person taken with different cameras) can substantially decrease matching decision accuracy (see Young & Burton, 2017 for a review).…”

Metacognitive Control and Lineup Instructions: Asking eyewitnesses to recollect reduces false identification

“…Participants studied multiple targets and made identification decisions about a four-person lineup for each. This paradigm allowed collection of multiple data points per participant and stimulus to increase statistical power and initial generalisability, and lineup accuracy and response strategies have been shown to remain stable over multiple trials (Mansour et al, 2017). Alternative single lineup paradigms limit generalisability and require large samples, so their ecological validity is more valuable at a later stage of procedural development.…”