Person recognition: Qualitative differences in how forensic face examiners and untrained people rely on the face versus the body for identification

Professional forensic face examiners surpass untrained individuals on challenging face-identity matching tasks. We investigated qualitative/ strategic differences in how forensic face examiners versus untrained people perform identity-matching tasks by analysing item responses (ratings of the likelihood that two images show the same person). We developed a novel analysis for quantifying item difficulty for participant groups and establishing group "winners" for items in conditions of interest. "Wisdom-of-the-crowds" effects were explored by fusing responses from varying numbers of participants to amplify strategic differences across groups. Results indicated that examiners use the internal face more effectively than untrained participants, but failed to exploit identity information in the external face and body. We also show that accuracy measures for examiners and controls must include both same-identity verifications and different-identity rejections to understand the role of perceptual skill and response bias in performance differences across participant groups.