ROCs in Eyewitness Identification: Instructions versus Confidence Ratings

From the perspective of signal detection theory, different lineup instructions may induce different levels of response bias. If so, then collecting correct and false identification rates across different instructional conditions will trace out the receiver operating characteristic (ROC)—the same ROC that, theoretically, could also be traced out from a single instruction condition in which each eyewitness decision is accompanied by a confidence rating. We tested whether the two approaches do in fact yield the same ROC. Participants were assigned to a confidence rating condition or to an instructional biasing condition (liberal, neutral, unbiased, or conservative). After watching a video of a mock crime, participants were presented with instructions followed by a six-person simultaneous photo lineup. The ROCs from both methods were similar, but they were not exactly the same. These findings have potentially important policy implications for how the legal system should go about controlling eyewitness response bias.