A dissociation in naming digits and colors following commissurotomy

Abstract

Pairs of red and green digits were flashed in the opposite visual fields of L.B., a man with complete forebrain commissurotomy. He was highly accurate in naming both digits, the green ones alone, or the red ones alone, regardless of field. In contrast, he was relatively poor at naming the colors of the digits in the left visual field, and in comparing colors between fields. This dissociation suggests either (a) that information about shape was tagged by color and transferred from right to left hemisphere, but information about color itself was not transferred, or, more likely (b) that L.B.'s right hemisphere has acquired the ability to overtly name highly familiar stimuli, such as digits, but not colors.