Numeric and Verbal Eyewitness Confidence: Order Effects

While verbal and numeric confidence may similarly predict identification accuracy, there are many challenges to overcome in the use of verbal confidence, despite the criminal justice system’s preference for it. Eyewitnesses could potentially provide scale ratings after verbal judgments or vice versa, if the confidence-accuracy relationship is maintained. In two studies, participants watched one or more mock-crime videos and then viewed target-present or target-absent lineups for the perpetrators. After each lineup, participants provided confidence either verbally (in their own words) and then numerically (0-100%), or numerically and then verbally. For verbal confidence judgments and numeric confidence judgments, neither order nor the interaction predicted identification accuracy. Asking eyewitnesses to provide confidence both verbally and numerically does not negatively impact the confidence-accuracy relationship, regardless of order. However, we show that there is considerable variability in the meaning eyewitnesses assigned to their own word confidence judgments, which suggests asking for own words confidence only is problematic. We caution that the usefulness of verbal confidence to predict accuracy hinges on a systematic approach to its interpretation.