Why does eyewitness verbal confidence add diagnostic value? A metacognitive noise account.

Police in many countries routinely ask eyewitnesses to state how confident they are after making an identification. Prior work suggests that verbal (e.g., "I'm very certain") and numeric (e.g., "80%") confidence provide nonredundant diagnostic information, but it is unclear whether this reflects distinct cognitive processes or simply the value of collecting multiple judgments. In two experiments (Experiment 1: N = 698, Experiment 2: N = 1,614), participants viewed 12 photo lineups and provided confidence ratings using verbal, numeric, slider (Experiment 1), and visual (Experiment 2) formats in counterbalanced order. While competing theories were tested-including multiretrieval-process and evidence accumulation accounts-the results favored a metacognitive noise account, where each confidence judgment is a noisy estimate of memory strength and averaging across judgments improves accuracy prediction. These findings inform both policing practices and basic science theories of metacognition. (PsycInfo Database Record (c) 2026 APA, all rights reserved).