A new approach to diagnosing and researching developmental prosopagnosia: Excluded cases are impaired too

Abstract

Developmental prosopagnosia is characterized by severe, lifelong difficulties when recognizing facial identity. Unfortunately, the most common diagnostic assessment (Cambridge Face Memory Test) misses 50–65% of individuals who believe that they have this condition. This results in such excluded cases’ absence from scientific knowledge, effect sizes of impairment potentially overestimated, treatment efficacy underrated, and may elicit in them a negative experience of research. To estimate their symptomology and group-level impairments in face processing, we recruited a large cohort who believes that they have prosopagnosia. Matching prior reports, 56% did not meet criteria on the Cambridge Face Memory Test. However, the severity of their prosopagnosia symptoms and holistic perception deficits were comparable to those who did meet criteria. Excluded cases also exhibited face perception and memory impairments that were roughly one standard deviation below neurotypical norms, indicating the presence of objective problems. As the prosopagnosia index correctly classified virtually every case, we propose it should be the primary method for providing a diagnosis, prior to subtype categorization. We present researchers with a plan on how they can analyze these excluded prosopagnosia cases in their future work without negatively impacting their traditional findings. We anticipate such inclusion will enhance scientific knowledge, more accurately estimate effect sizes of impairments and treatments, and identify commonalities and distinctions between these different forms of prosopagnosia. Owing to their atypicalities in visual perception, we recommend that the prosopagnosia index should be used to screen out potential prosopagnosia cases from broader vision research.

Balanced Integration Score: A new way of classifying Developmental Prosopagnosia

“…The CFMT is the gold standard test for detecting DP, but even on this test 107/165 (65%) participants did not meet strict cut off criteria ( -2 SD). Burns et al (2022) also report that a similar proportion of DPs (56%) did not score more than 2 SD below controls means on the CFMT.…”

“…The criteria to classify DP vary between research groups, which is problematic for study and case comparison (Corrow et al, 2016). To address this, Dalrymple and Palermo (2016) recommended that in addition to subjective reports of face recognition difficulties, individuals should exhibit impairments on at least two objective tests of face processing (cf., Burns et al, 2022). Notably these guidelines did not specify that these should test face recognition (as opposed to face perception) specifically.…”

“…How researchers choose to define study inclusion and exclusion for the DP and control groups has important implications for our ability to fully understand DP. A key question is why so many individuals who report severe problems recognising familiar faces in everyday life do not appear to meet the classification for DP (for a discussion see Burns et al, 2022 andDeGutis et al, 2022b)? For example, a recent large-scale study of 165 adults who reported severe everyday face recognition problems (Bate et al, 2019) showed that 61.8% of the 165 suspected DPs did not meet the commonly used diagnostic threshold of at least 2 SDs below control means on a minimum of two of the three commonly-used diagnostic tests.…”

“…The studies by Bate and colleagues (2019) and Burns et al, (2022) are relatively unusual in assessing the performance of all the self-reported DPs. More commonly in the literature only those participants who meet strict objective criteria for DP are included in studies (for a review see DeGutis et al, 2022b).…”

“…More commonly in the literature only those participants who meet strict objective criteria for DP are included in studies (for a review see DeGutis et al, 2022b). Unnecessary exclusion of a high proportion of potential participants who report this rare condition is problematic, both for practical and, arguably, ethical reasons (Burns et al, 2022).…”