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The number of fillers may not matter as long as they all match the description: The effect of simultaneous lineup size on eyewitness identification

NCJ Number
Applied Cognitive Psychology Volume: 34 Issue: 3 Dated: 2022 Pages: 590-604
Alex R. Wooten; Curt A. Carlson; Robert F. Lockamyeir; Maria A. Carlson; Alyssa R. Jones; Jennifer L. Dias; Jacob A. Hemby
Date Published
15 pages

According to the Diagnostic Feature-Detection (DFD) hypothesis, the presence of fillers that match the eyewitness's description of the perpetrator will boost discriminability beyond a showup, and very few fillers may suffice to produce the advantage, so we tested this hypothesis by comparing showups with simultaneous lineups of size 3, 6, 9, and 12.


Participants (N = 10,433) were randomly assigned to one of these conditions, as well as target-present (TP) versus target-absent (TA) lineup. As predicted by the DFD hypothesis, lineups were superior to showups, and there was no advantage with increased lineup size beyond a 3-member lineup. The confidence-accuracy (CA) relationship held a similar pattern. The only effect of increased lineup size was a lower likelihood of choosing a suspect (guilty or innocent). We conclude that police should focus more on the quality rather than quantity of fillers. (Publisher abstract provided)