Perceptual, semantic and phonetic aspects of elementary language processes in split-brain patients.

Patients with total forebrain commissurotomy were examined on three tests of elementary linguistic ability. We found that the right hemisphere was dominant for the visual recognition of words when no semantic or phonetic decoding was required. The left hemisphere assumed control of behaviour when written words had to be matched semantically to pictures, though the right hemisphere was also competent at this task. On a test of rhyming, the left hemisphere was not only dominant, but was vastly superior to the right which displayed little, if any, ability. We suggest that the two hemispheres are basically differentiated with respect to their generative, constructive capacities in language, as in other functions of intelligence.