Decision Processes in Eyewitness Identification

Doctoral thesis English OPEN
Moreland, Molly Bettis (2015)
  • Publisher: eScholarship, University of California
  • Subject: Psychology | decision making | eyewitness identification | memory

The dominant theory of decision-making in eyewitness identification, based on a distinction between absolute and relative judgments, assumes that relative judgments (identifying the best match relative to the other lineup members) increases identification errors (Wells, 1984). This distinction also assumes that comparisons among lineup members underlying relative judgments increases errors, as evidenced by the sequential lineup advantage (Lindsay & Wells, 1985). Sequential lineups preclude comparisons among lineup members by presenting lineup members separately. Recently, and in contrast to the dominant view, receiver operating characteristic (ROC) studies found a simultaneous accuracy advantage (Mickes, Flowe, & Wixted, 2012) that may be due to underlying comparative processes (Wixted & Mickes, 2014). This dissertation focuses on the effect of comparative strategies on eyewitness identification accuracy. Clark, Erickson, and Breneman (2011) simulated identification response probabilities for different decision rules and foil selection methods using the computational model, WITNESS (Clark, 2003). These simulations showed a disadvantage for relative judgment strategies for lineups with foils matched to the appearance of the suspect. Experiment 1 provides an empirical test of the WITNESS model's predictions. Participants viewed lineups that differed in suspect guilt or innocence and foil selection method. The innocent suspect either appeared in different-foils lineups, the foil selection method used by police, or same-foils lineups, a method used in eyewitness identification research that holds foils constant across lineup type. Additionally, lineup instructions either directed witnesses to use an absolute or relative judgment decision rule. ROC curves indicated a small advantage for relative decision rules for different-foils and same-foils lineups. Contrary to the dominant view, the results suggest that relative judgments (and comparisons among lineup members) may improve accuracy. Experiment 2 investigated comparative processes independently of decision rule. Participants viewed lineups that differed in arrangement. Similar foils surrounded the suspect in the high-similarity neighbor condition, designed to facilitate comparative processes, and dissimilar foils surrounded the suspect in the low-similarity neighbor condition. Results showed an accuracy advantage for high-similarity neighbors based on ROC analyses. Experiment 3 investigated the degree to which comparisons among lineup members underlie the simultaneous accuracy advantage. Witnesses viewed lineups differing in lineup presentation (simultaneous or sequential), and neighboring foil similarity. Results showed a larger accuracy advantage of simultaneous high-similarity neighbor lineups. High-similarity neighbors may facilitate comparative strategies in simultaneous lineups but not sequential lineups, corroborating recent reports of a simultaneous advantage and contrary to the widespread "sequential superiority" view.
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