Adaptation of the 20-Item Prosopagnosia Index for the screening of developmental prosopagnosia in Mexico

Abstract Developmental prosopagnosia (DP) is a lifelong condition characterized by difficulties in recognizing faces despite intact vision and intelligence. The 20-Item Prosopagnosia Index (PI20) is a widely used self-report instrument for screening face recognition deficits. However, no standardized Spanish version of the PI20 existed prior to this study, limiting its applicability in Spanish-speaking populations. This study aims to adapt and validate the PI20 for use in Mexican Spanish, ensuring its linguistic, cultural, and psychometric applicability for the Mexican population. Study 1 involved a rigorous translation and cultural adaptation process, including forward translation by multiple independent translators, expert panel review, and cognitive interviews with bilingual Mexican participants. Qualitative analysis of these interviews identified semantic and conceptual issues in several items, which were subsequently revised. A pilot test with 15 participants confirmed the clarity and feasibility of the adapted version, supporting its content validity. Study 2 evaluated the psychometric properties of the adapted PI20 in a sample of 333 adults. The results showed high internal consistency (McDonald’s omega and Cronbach’s alpha = .84) and good test–retest reliability (ICC2,1= .81). Confirmatory factor analysis supported a unidimensional structure consistent with the original scale, while exploratory analysis revealed two correlated components that did not undermine the overall model. The adapted PI20 showed a moderate negative correlation with the Cambridge Face Memory Test (r=-.229, p<.001), confirming convergent validity, and no significant association with the Cambridge Car Memory Test (r=-.106, p=.061), supporting discriminant validity. These findings demonstrate that the Mexican Spanish version of the PI20 is a reliable and valid tool for assessing DP in Spanish-speaking populations. This culturally adapted instrument can facilitate screening in clinical and research settings and contribute to a better understanding of face recognition difficulties across diverse linguistic and cultural groups. Competing Interest Statement The authors have declared no competing interest. Funding Statement MM received funding from the Institutional Research Coordination (Project #517) of CETYS University. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical approval was obtained from the Research Ethics Committee of CETYS University (#D-CEI154). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability All the translation materials, anonymized participant data, and analysis scripts can be found on this paper's project page on the https://osf.io/k8vwt/?view_only=289b9c1da7684c3baffe29a8604d15a5 https://osf.io/k8vwt/?view_only=289b9c1da7684c3baffe29a8604d15a5