Variations in "same"-"different" judgments in patients with unilateral cortical lesions.

Five subject groups (normal controls, left anterior lesion patients, left posterior lesion patients, right anterior lesion patients, right posterior lesion patients) were tested on two perceptual matching tasks. All groups performed comparably accurately, although right hemisphere lesion patients demonstrated longer RT scores for "same" than for "different" judgments, whereas left hemisphere lesion patients demonstrated the reverse effect. Increased perceptual complexity of "same" target produced higher RT scores for "different" responses in right (but not left) hemisphere lesion groups. Finally, high-prototypicality "same" targets yielded lower RT scores than low-prototypicality "same" targets for all groups.