One bird with two stones? The development and testing of two abbreviated versions of the 20-item Prosopagnosia Index

Developmental prosopagnosia (DP) is a neurodevelopmental disorder characterized by profound difficulties with face recognition. While there are no commonly agreed criteria for classifying individuals with DP, most researchers utilize self-report measures as an essential part. Here, we report the outcome from two teams who independently examined and tried to improve the most widely used tool in the field: the 20-item Prosopagnosia Index (PI20). The two teams arrived at a 13-item solution (PI13) and a 5-item solution (PI5), respectively. Joining forces, we tested both abbreviated versions and the original PI20 in a prospective investigation, with the aim of validating and comparing the tools. We found that PI5 and PI13 provide valid and reliable assessment of face recognition problems, and we recommend PI5 as a screening tool for face recognition problems with potential for use in clinical settings, while PI13 may be better suited for research on individual differences in face recognition.