VISUAL EXTINCTION AND STIMULUS REPETITION

Five patients with visual extinction following unilateral brain injury were briefly presented with colored letters in either or both visual fields, and required to report and locate the colors or the shapes. on double simultaneous stimulation, they tended to miss the event contra lateral to their lesion. This extinction was increased when the two st imuli were the same on the reported dimension. Similarity on the irrel evant dimension had no effect. These data suggest that extinguished co lors and shapes may be correctly extracted by the visual system (when task-relevant) even though they are unavailable for verbal report. An analogy is made with the phenomena of ''repetition blindness'' in norm al observers, and it is proposed that extinction may reflect failure i n a token-individuation process for correctly extracted visual types.