A model of position effects in the sequential lineup

Abstract

What is the effect of placing the suspect in different positions in a sequential lineup? To explore this question, we developed and applied a model called the Independent Sequential Lineup model which analyzes a sequential lineup in terms of both identification position, the position at which the witness identifies a lineup item as the target, and target position, the position at which the target or suspect appears. We conducted a large-scale online eyewitness memory experiment with 7,204 participants each of whom was tested on a 6-item sequential lineup with an explicit stopping rule. The model fit these data well and revealed systematic effects of lineup position on underlying discriminability and response criteria. We also fit the model to data from a similar pair of experiments conducted recently by Wilson, Donnelly, Christenfeld and Wixted (2019; Journal of Memory and Language, 104, 108–125) both with and without application of a stopping rule. In all data sets, if a stopping rule is applied, underlying discriminability was found to be constant, or to increase slightly, across target position. In the absence of a stopping rule, discriminability was found to decrease substantially. We also observed a substantial increase in response criteria following presentation of the target. We discuss the implications of these findings for current theories of recognition memory and current applications of the sequential lineup in different jurisdictions.