Only one study has evaluated the utility of the appearance change instruction (ACI; Charman & Wells 2007). This study found that the ACI actually harms eyewitness performance in lineups such that false identifications are increased without any increase in correct identifications compared to those eyewitnesses who do not receive the ACI. The authors proposed two theories that may explain these findings; an alteration of ecphoric similarity through “mental mutation” or a decision criterion shift. This proposal will report on