Understanding the cognitive mechanisms of developmental prosopagnosia

Developmental prosopagnosia (DP) is a condition associated with severe difficulties recognising familiar faces, which occurs in individuals with normal intelligence, typical low-level vision, and in the absence of manifest brain injuries. The neuro-cognitive origins of DP are still debated. Cognitive accounts have attributed face recognition deficits to reduced holistic processing of faces (i.e., whereby individual features of faces are integrated into a unified perceptual whole), and mnemonic difficulties, whereby prosopagnosics may be able to form accurate percepts, but are unable to maintain those percepts over time. At the neurological level, differences have been reported in the structural and functional connectivity of occipito-temporal regions which include face selective areas. Chapter 2 of this thesis investigated facial emotion recognition in DP and revealed widespread difficulties recognising facial emotion in individuals with apperceptive profiles of DP (i.e., DPs exhibiting difficulties forming view-invariant structural descriptions of faces at early stages of encoding). Chapter 3 explored body recognition in DP and found evidence of impaired body and object recognition in DP individuals. Moreover, the lack of relationship between observers’ object and body recognition performances suggested that body and object recognition impairments in DP may co-occur independently. Chapter 4 investigated the susceptibility to the composite face illusion in two independent samples of individuals with DP and failed to show evidence of diminished composite face effects in both samples. Finally, Chapter 5 considered the contribution of perceptual encoding and short term face memory in DP using a delayed match-to-sample task and found that recognition impairments in prosopagnosics were insensitive to changes in retention interval and viewing angle, supporting an apperceptive characterisation of DP. The implications of these findings for the characterisation of DP and for understanding its underlying cognitive mechanisms, are discussed in Chapter 6