The role of scanpaths in facial recognition and learning

We carried out a comprehensive assessment of eye movements in 2 subjects with impaired facial learning and recognition to determine if the defect might be associated with abnormal scanning of faces. Standard electroculogram showed that fixation, pursuit, saccades, and scanning of salient features of scenes and faces were normal, indicating that the defect was not due to abnormal scanning. However, study of the transitional properties of scanning revealed that the scanpaths of personally meaningful familiar faces, whether or not they were consciously recognized, were less predictable than those of other faces. This result indicates the existence of an internal and relatively specific schema for familiar faces sufficient to alter the "predictable" scanpath used for nonfamiliar faces. This internal schema is accessed even when conscious recognition fails, i.e., when other pertinent memories related to the possessor of the face are not evoked. The meaning of this finding is comparable to that obtained with autonomic studies of covert recognition in prosopagnosia and suggests that properties of scanning can be used as an index of higher neural processing.