A dissociation between spatial and identity matching in callosotomy patients.

Although they are structurally similar, the two hemispheres of the human brain have many functional asymmetries. Some of these, such as language and motor control, have been well characterized. Others, such as visuospatial asymmetries, are less well understood. Many researchers have noted that the right hemisphere appears to be specialized for visuospatial processing. We investigated the abilities of the divided cerebral hemispheres of two callosotomy patients to perform discriminations based on spatial or identity information. The data revealed a robust right-hemisphere superiority for spatial judgments. In contrast, the left hemisphere was somewhat better than the right at making identity judgments. These results suggest that the right hemisphere is specialized for spatial processing, and the left is specialized for pattern recognition.