Fast and Confident: Postdicting Eyewitness Identification Accuracy in a Field Study

The combined postdictive value of postdecision confidence, decision time, and Remember-Know-Familiar (RKF) judgments as markers of identification accuracy was evaluated with 10 targets and 720 participants. In a pedestrian area, passers-by were asked for directions. Identifications were made from target-absent or target-present lineups. Fast (optimum time boundary at 6 seconds) and confident (optimum confidence boundary at 90%) witnesses were highly accurate, slow and nonconfident witnesses highly inaccurate. Although this combination of postdictors was clearly superior to using either postdictor by itself these combinations refer only to a subsample of choosers. Know answers were associated with higher identification performance than Familiar answers, with no difference between Remember and Know answers. The results of participants' post hoc decision time estimates paralleled those with measured decision times. To explore decision strategies of nonchoosers, three subgroups were formed according to their reasons given for rejecting the lineup. Nonchoosers indicating that the target had simply been absent made faster and more confident decisions than nonchoosers stating lack of confidence or lack of memory. There were no significant differences with regard to identification performance across nonchooser groups.