A commissurotomy patient with limited language in the right hemisphere was tested for ability to recognize direct and indirect antonyms. Normal subjects performing this task recognize direct antonyms faster than indirect. The patient's left hemisphere responded normally, but his right showed no difference in response to direct and indirect antonyms. It is concluded that the patient's right hemisphere had not learned that particular pairs of adjectives (the direct antonyms) can be used to represent the attribute whose contrasting values they express. Such learning normally occurs in the course of reasoning about attributes of things and events, but presumably failed to occur in this patient's right hemisphere because its powers of reasoning are severely limited.

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