Prosopagnosia

Prosopagnosia is a neurological deficit characterised by the inability to recognise the faces of previously known persons in the absence of severe intellectual, sensory or cognitive impairments. Although prosopagnosic patients usually experience a total absence of a feeling of familiarity with faces of known individuals and a failure of overt recognition of these faces, it has been shown that the processing of familiar faces can still take place in the absence of the patient’s awareness.

This was demonstrated by physiological [skin conductance (Bauer & Verfaellie, 1988; Tranel & Damasio, 1985), pupillometry (Etcoff et al., 1991), and event related potentials (Renault et al., 1989; Small, 1988)] and behavioural indices (Bruyer et al., 1983; de Haan et al., 1987; Sergent & Poncet, 1990) of recognition showing significant differences in response to familiar and unfamiliar faces (see (Bruyer, 1991) for a review). Bruyer (1991) defines a further area of behavioural study for the covert recognition of faces, namely, the recording of eye movements (Bruyer, 1991). Neurologically-intact perceivers tend to adopt a facial feature scanning strategy (Luria & Strauss, 1978), i.e., they explore preferentially the ‘eyes’, ‘nose’, and ‘mouth’ (Walker-Smith et al., 1977). The recording of eye movements in two patients with impaired facial learning and recognition showed that fixation, pursuit, saccades, and scanning of salient features of scenes and faces were normal (Rizzo et al., 1987).

However, the study of the transitional properties of scanning revealed that the scan paths of personally meaningful familiar faces, whether or not they were consciously recognized, were less predictable than those of other faces (Rizzo et al., 1987). This suggested that as autonomic studies of covert recognition in prosopagnosia, the properties of scanning can be used as an index of higher neural processing.