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.
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