Abstract
Introduction: In recent years, the number of face identity matching tests in circulation has grown considerably and these are being increasingly utilized to study individual differences in face identity processing. Although many of these tests were designed for testing typical observers, recent studies have begun to utilize general-purpose tests for studying specific, atypical populations (e.g., super-recognizers and individuals with prosopagnosia). In this study, we aimed to determine the capacity of four frequently used face matching tests requiring binary 2AFC decisions as a means of assessing individual differences between healthy observers. Uniquely, we used performance of the patient PS (Rossion, 2018), a well-documented case of acquired prosopagnosia (AP), as a benchmark. Method: PS completed four tests of face identity matching – the Person Identity Comparison Test (PICT), the Expertise in Facial Comparison Test (EFCT), the Glasgow Face Matching Test (GFMT), and the Kent Face Matching Test (KFMT). Her accuracy, response times, and inverse efficiency were compared against a sample of younger controls and age-matched controls for each test. Results: Compared to age-matched controls and despite considering both accuracy and response speed to account for potential trade-offs, only the KFMT was able to detect PS’s severe impairment. Strikingly, for the EFCT, PICT, and GFMT, PS achieved performance that was within the normal range. Conclusion: Our results reflect that tests that fail to distinguish highly impaired individuals such as PS from normal observers are limited in their capacity to measure individual differences in neurotypical observers. More generally, these findings emphasize the need for systematically comparing tests in terms of their sensitivity to study human cognition and brain functioning. Critically, obtaining a detailed understanding of both test sensitivity and individual ability requires considering both observers’ accuracy and response times.