Break-down of perceptual awareness in unilateral neglect.

Four neglect patients are reported who where unable to detect left-side differences in pairs of drawings though being sometimes influenced by such differences in making preference judgements. In most instances, tracing the silhouette of the drawings did not help patients to find the difference despite the fact that tracing implied crossing the altered detail or following its contour with the fingertip. This finding cannot easily be accommodated by current theories of unilateral neglect.