Evidence of covert recognition in a prosopagnosic patient.

This is a case-study of a patient (ET) who suffers from prosopagnosia, in the context of impairment to cognitive functions, following traumatic brain injury. Despite severe perceptual difficulties in tests involving non-face stimuli and matching unfamiliar faces, ET showed evidence of "covert" recognition of familiar faces in a number of tasks. Although densely prosopagnosic, she performed at normal levels in word and object recognition tasks, and is unimpaired in her ability to recognise names of celebrities. She performed at the same level as controls in her ability to make a forced-choice of the correct name for a famous face, even though it evoked no feeling of familiarity for her. She performed at chance in a forced-choice face familiarity decision task, but showed evidence of covert recognition in a "true" versus "untrue" face-name learning task. ET showed overt recognition of some famous faces using a procedure based on Sergent and Poncet's (1990) semantic activation task. The pattern of impairment of ET's face processing abilities is interpreted in terms of an interactive activation model of face processing.