Reversed perceptual asymmetry for faces in left unilateral neglect.

Twelve patients with left unilateral neglect and 12 matched controls were examined on two tests of face perception. In the chimeric faces task, subjects were required to make a judgement of happiness on pairs of photographic chimeras, while in the face-matching task, they were required to indicate which of two symmetrical face composites more closely resembled the original. Whereas controls showed a significant leftward perceptual bias on both tasks, left neglect patients showed an even stronger rightward (reversed) perceptual bias. Patients with and without left-sided visual field defects exhibited the reversed asymmetry, and the degree of perceptual bias shown by patients was not related to the severity of their symptoms as measured by standard clinical tasks. There was no relationship between the extent of rightward bias exhibited by patients or controls on the two tasks. These results contribute to our understanding of the mechanisms underlying unilateral neglect. Moreover, the tasks themselves may be employed as a simple and sensitive adjunct to the clinical assessment of this disorder.