Subjective Face Recognition Ability Is Linked to Objective Face Memory and Face Authenticity Judgment: Validation of the Traditional Chinese Version of the 20-Item Prosopagnosia Index

<b>Background/Objectives:</b> Developmental prosopagnosia (DP) is a neurodevelopmental disorder marked by lifelong face recognition difficulties. The 20-item Prosopagnosia Index (PI-20) has become an important tool for screening individuals with DP and has been validated across various groups of English speakers worldwide. Recently, other language versions of PI-20, such as a Simplified Chinese one, have been developed and validated. Given the significant differences between Simplified Chinese and Traditional Chinese, as well as the distinct user populations, this study aims to validate a Traditional Chinese adaptation of the PI-20 using a standardized face memory task and a novel face authenticity judgment task in Mandarin-speaking populations. <b>Methods and Results:</b> In Study 1 (<i>n</i> = 94) and Study 2 (<i>n</i> = 138), we tested two large independent samples of college students using the English PI-20 and the Traditional Chinese PI-20, respectively. The results show strong internal consistency and similar score distributions in both versions of the PI-20. In Study 3 (<i>n</i> = 64), we examined the correlation between PI-20 scores and performance on the Cambridge Face Memory Test (CFMT). We found a significant correlation with the CFMT score and the Traditional Chinese version, but not with the English version PI-20. In Study 4 (<i>n</i> = 32), we examined whether PI-20 scores correlated with a face authenticity judgment task where participants judged whether the face image was real or AI-synthesized. Results showed that PI-20 negatively correlated with accuracy in judging real faces, but not with judging AI-synthesized faces. <b>Conclusions:</b> Overall, this study shows that although Taiwanese participants validly respond to the original PI-20, the Traditional Chinese version exhibited a stronger association with their objective face memory skills and showed a link to participants' knowledge about real faces, which is a new finding. The Traditional Chinese PI-20 can serve as a dependable and useful tool in future research.