Associations and dissociations between face detection and face individuation in developmental prosopagnosia

Face recognition is a fundamental brain function that involves multiple processing stages. Two key stages are face detection, the process of classifying a stimulus as a face, and face individuation, the process of discriminating one face from another face. In this thesis I used developmental prosopagnosia (DP) to investigate the relationship between face detection and face individuation. DP is a lifelong neurodevelopmental condition characterised by impaired face individuation, but whether face detection is also impaired in DP remains unclear. I assessed face detection in a large sample of 52 individuals with DP using three experimental tasks: a Mooney face task, a pareidolia face task, and a visual search task. The results are mixed. DP participants showed marked impairments on the Mooney task, subtle impairments on the visual search task, but normal performance on the visual search task. Correlation analyses produced patterns of associations and dissociations depending on tasks. Together, these results suggest that face detection is a complex function that can be spared or impaired in DP depending on the specific mechanisms and task demands. This finding demonstrates both associations and dissociations between face detection and face individuation in DP. The nuanced relationship between face detection and face individuation adds to our understanding of the etiology of DP and our theoretical model of processing stages in face recognition.