The effects of instructions on performance in lineups and showups

Various preidentification instructions have been proposed to reduce eyewitness misidentifications by promoting conservative responding. According to the classic signal detection model, such instructions should shift decision criteria without affecting discriminability-the ability to distinguish innocent from guilty suspects. Yet, in prior research, while two types of instructions did make participants respond more conservatively, one type of instruction decreased discriminability and another increased discriminability. Across four experiments-three conducted online and one in the field-we tested the effects of different instructional methods on eyewitness responding in both lineup and showup procedures. We found that while certain instructions consistently induced more conservative responding, they sometimes decreased and never increased discriminability. We attribute this pattern to instructional variance: participants likely interpreted and complied with the instructions to varying degrees, introducing noise that lowered discriminability. Notably, identifications made with high confidence were associated with much more conservative responding than any instruction alone, suggesting that conservative responding is best achieved by collecting confidence rather than by instructing eyewitnesses to respond conservatively. Finally, the confidence-accuracy relationship was stronger in our field showup using live actors than in the corresponding online version, underscoring the need for more research in the field to better understand eyewitness identification performance. (PsycInfo Database Record (c) 2026 APA, all rights reserved).