Academic journal article Psychonomic Bulletin & Review

Revisiting Absolute and Relative Judgments in the WITNESS Model

Academic journal article Psychonomic Bulletin & Review

Revisiting Absolute and Relative Judgments in the WITNESS Model

Article excerpt

Published online: 14 August 2013

© Psychonomic Society, Inc. 2013

Abstract The WITNESS model (Clark in Applied Cognitive Psychology 17:629-654, 2003) provides a theoretical framework with which to investigate the factors that contribute to eyewitness identification decisions. One key factor involves the contributions of absolute versus relative judgments. An absolute contribution is determined by the degree of match between an individual lineup member and memory for the perpetrator; a relative contribution involves the degree to which the best-matching lineup member is a better match to memory than the remaining lineup members. In WITNESS, the proportional contributions of relative versus absolute judgments are governed by the values of the decision weight parameters. We conducted an exploration of the WITNESS model's parameter space to determine the identifiability of these relative/absolute decision weight parameters, and compared the results to a restricted version of the model that does not vary the decision weight parameters. This exploration revealed that the decision weights in WITNESS are difficult to identify: Data often can be fit equally well by setting the decision weights to nearly any value and compensating with a criterion adjustment. Clark, Erickson, and Breneman (Law and Human Behavior 35:364-380, 2011) claimed to demonstrate a theoretical basis for the superiority of lineup decisions that are based on absolute contributions, but the relationship between the decision weights and the criterion weakens this claim. These findings necessitate reconsidering the role of the relative/absolute judgment distinction in eyewitness decision making.

Keywords Eyewitness identification . Relative and absolute judgments . Computational modeling . WITNESS model

One of the most unfortunate consequences of a legal system governed by human judgment is the alarming occurrence of false eyewitness identifications; too many individuals have been in- carcerated for crimes that they did not commit. Many factors contribute to false convictions, but the principal one is faulty eyewitness identification, which contributed to the convictions in 75% of the DNA exonerations (see www.innocenceproject.org/).

A major contributor to faulty eyewitness identification is thought to be an overreliance on relative judgments (Wells, 1984). A relative judgment can involve making a selection of the lineup member who most resembles the perpetrator rela- tive to the other lineup members, which can arise when comparisons are made across lineup members. Obviously, this is problematic if the police have an innocent suspect who is compared to foils that poorly resemble the perpetrator. On the other hand, an absolute judgment involves choosing the best- matching lineup member if, and only if, the degree of match to memory is above a criterion value. It is believed that a reliance on absolute judgments would enhance the accuracy of eye- witness identifications. This is the rationale for the recommen- dation that lineups be conducted sequentially (with lineup members being presented one at a time; e.g., Wells et al., 1998; for a review, see Gronlund, Andersen, & Perry, 2013).

To evaluate this distinction, Wells (1993) developed the removal-without-replacement paradigm. This paradigm re- quires the creation of two lineups. In one lineup (the target- present lineup, which includes the perpetrator/guilty suspect), the guilty suspect is presented along with five foils. In the other lineup (the target-removed lineup), the guilty suspect is removed and NOT replaced, creating a five-person lineup. Suppose that 50% of a randomly assigned sample of partici- pants correctly selected the guilty suspect from a target- present lineup and 20% rejected the lineup. Wells argued that if participants rely on absolute judgments, approximately 70% of the participants in the target-removed lineup should reject the lineup. This would consist of the 50% of participants who would reject because they did not see the perpetrator that they otherwise could identify, plus the 20% who rejected the lineup anyway. …

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