The effect of lineup member similarity on recognition accuracy in simultaneous and sequential lineups

Prior research suggests that simultaneous lineup procedures, which involve presenting at once all of the alternatives, encourage witnesses to identify the relatively most familiar face. In contrast, when lineup alternatives are evaluated one at a time, or sequentially, identifying a face is not influenced by previously seen faces in the lineup. Instead, a face will be chosen from a sequential lineup only when it is a sufficient match to the perpetrator in memory. The present study investigated whether face discrimination differs between simultaneous and sequential lineups. In particular, if the retrieval process is influenced by comparing the faces during the decision process, then the similarity of the alternatives with respect to the perpetrator should influence accuracy only in simultaneous lineups. Overall, positive identifications of the target, whether identical to the study face or a feature substituted version of the study face, were higher in simultaneous lineups, while misses occurred with greater frequency in sequential lineups. We also found that in both simultaneous and sequential presentations, decreasing the similarity of the alternatives increased the rate at which the innocent suspect was identified. In addition, if an alternative that was similar to the study face was presented before the target, sequential participants tended to identify it and miss the target face as a result. When the target was removed from the lineup, there was a tendency in both simultaneous and sequential conditions to choose the alternative that was the highest in similarity with respect to the target. Accuracy was correlated with lineup fairness and similarity measures, and the pattern of findings was similar across identification procedures. A final set of studies examined whether choice rates in sequential presentations are lower because participants have a higher identification threshold than simultaneous participants. To investigate, the number of features that varied across the alternatives was manipulated, in addition to whether participants were forced to choose a face or given the option not to choose. Accuracy was higher in simultaneous compared to sequential lineups when fewer features were available for discriminating between the faces in the lineup. However, under forced choice conditions, differences in accuracy between identification procedures were significantly decreased, suggesting that not being able to compare the faces might lead witnesses to adopt a higher decision criterion. The findings from the series of studies reported are evaluated with respect to theoretical models of eyewitness identification.