Abstract
Developmental prosopagnosia (DP) has shown to be a heterogeneous disorder (e.g., presence/absence of face detection deficits, presence/absence of a face-selective N170). Though there have been suggestions of possible DP sub-types (e.g., those with face-specific deficits vs. general object processing deficits), because of the relatively low sample sizes of most DP studies (N<15) these proposals have not been tested empirically. In the current study, we administered a battery of six perceptual and memory tests to 44 individuals who presented with clinical interview responses characteristic of developmental prosopagnosia (e.g., difficulty following characters on television and recognizing familiar people out of context). To characterize possible DP sub-types, we performed a hierarchical cluster analysis, using Ward's method to minimize total within-cluster variance. This produced three distinct clusters: the first included 13 participants with subjective face recognition complaints but with relatively minor face memory (z-score=-1.43) and face perception deficits (z-score average=-.96) and no significant holistic face processing deficits. The second (N=17) and third (N=14) clusters both had more severe face memory deficits (z-scores of -2.27 and -2.38, respectively) and demonstrated significant holistic face processing deficits. Interestingly, the third cluster also showed more severe deficits in face perception tasks (z-score average=-2.44) compared to the second cluster (z-score average=-1.5). Finally, none of the clusters differed in object perception, suggesting that this ability does not differentiate between DP sub-types. These results suggest that one sub-group of individuals with subjective face recognition difficulty do not show significant impairment on objective tests, questioning whether they should be considered prosopagnosic. Furthermore, our results suggest that individuals with more severe face recognition impairments can be divided into those with more and less severe face perceptual abilities. Together, this suggests that developmental prosopagnosia should not be considered a unitary category, and that dissociable mechanisms may cause very similar face recognition complaints.
Meeting abstract presented at VSS 2014