Are deficits in emotional face processing preventing perception of the Thatcher illusion in a case of prosopagnosia?

Abstract

Behavioural studies using the Thatcher illusion are usually assumed to demonstrate configurality in upright face processing. Previously, we have reported on PHD, an individual with prosopagnosia, could not discriminate Thatcherized faces but showed some evidence for residual face processing (VSS, 09). Recent functional imaging data suggests a role for emotional expression perception in discriminating Thatcherized from neutral faces (Donnelly & Hadjikhani, in preparation). Here we report on a series of emotion perception tasks were conducted on PHD and control participants. Results for PHD revealed: (1) specific deficits for distinguishing magnitude of anger and disgust; (2) poor sensitivity when discriminating faces as one of two given emotions; (3) a within category deficit for intensity, but no intensity deficit between emotions unless disgust was present; (4) a different solution for PHD relative to controls in respect of a multidimensional scaling study for sameness judgements of faces varying in emotion identity and intensity. We consider possible relationships between PHDs emotion perception and his ability to discriminate Thatcherised from normal faces.