A novel test for the investigation of prosopagnosia

Abstract

To clarify whether the prosopagnosic patients are in the same state of blind for faces or able to discriminate faces at subordinate level, we quantitatively investigated the face recognition impairment in patients, using a novel face recognition test (a same–difference judgment test and a similarity judgment test) with in-between faces superimposed by morphing. Although the accuracy of face discrimination in patients was very low, even a severe prosopagnosic patient tended to choose the same standard stimulus that normal subjects chose. These results indicate that prosopagnosia is not the same state of blind for faces but is the state with weakened categorical perception. It also suggests that the impaired perceptual level in prosopagnosic patients is determined by becoming an expert for a visual object. Additionally, our study clarified that the discrimination ability in prosopagnosic patients is not affected by semantic information about a familiar person unlike normal people.