Absolute and Relative Decision Processes in Eyewitness Identification

A prominent and long-standing theory of eyewitness identification decision making distinguishes between absolute judgments, based on the lineup members' match to the witness's memory of the perpetrator, versus relative judgments, based on match values relative to other lineup members. This distinction was implemented in a computational model and simulations showed that the model predicts an accuracy advantage for absolute judgments over relative judgments under some conditions. The present experiment tested this prediction by evaluating the accuracy of witnesses instructed to use relative or absolute rules. Contrary to predictions, the overall analysis did not show an absolute advantage. Additional exploratory analyses showed a relative advantage when the suspect was surrounded by high-similarity foils. These results are consistent with a model that assumes that side-by-side comparisons of lineup members increase diagnostic accuracy by allowing witnesses to give greater weight to more diagnostic features and less weight to less diagnostic features.