During the 1960's, researchers at the California Institute of Technology had the opportunity to study a small group of individuals who came to be known as "split-brain" patients.1 These patients had been greatly disabled by epileptic seizures involving the left and right hemispheres of the brain. As a last-resort measure, the incapacitating seizures between the two hemispheres were controlled by means of surgery that severed the corpus callosum and its related cross-connections, thus isolating one hemisphere from the other. The result of the operation was that the patients' seizures were controlled. In spite of the radical nature of the surgery, the patients' outward appearance, manner, and coordination were little affected; and to the casual observer their ordinary daily behavior seemed little changed.
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The Cal Tech research group subsequently worked with these patients in a series of tests that revealed the different functions of each hemisphere. The tests provided surprising evidence that each hemisphere, in a sense, perceives it own reality -- or perhaps better stated, perceives reality in its own way. The verbal half of the brain -- the left half -- dominates most of the time in individuals with intact brains as well as in the split-brain patients. But the right, non-verbal half of the brain also experiences, responds with feelings, and processes information on its own: it is different than, but not dumber than, its verbal twin.
One of the most revealing stories to come out of split-brain research involves a patient who was exposed to two different images at the same time. On the left side of a divided screen was a picture of a spoon; on the right side was a picture of a knife. The patient was asked to focus on a dot in the center of the screen as the two images were briefly projected. The picture of the spoon was "seen" by the non-verbal right brain -- but the picture of the knife was "seen" by the verbal left brain. When questioned, the patient gave different responses. If asked to name which had been flashed on the screen, the confidently articulate left hemisphere caused the patient to say "knife." But when the patient was asked to reach behind a curtain with his left hand and pick out what had been flashed on the screen, he picked out a spoon.
If the experimenter asked the patient to identify what he held in his left hand behind the curtain, the patient might look confused for a moment and then say "a knife." The right hemisphere, knowing that the answer was wrong, but not having sufficient words to correct its articulate counterpart, continued the dialogue by causing the patient to mutely shake his head. At that, the verbal left hemisphere wondered aloud, "Why am I shaking my head?"2
Why am I shaking my head?
Is it possible that, even when the two hemispheres of the human brain are communicating freely, the right brain knows more than it can tell?
What the Hemispheres Know
In a summary of the characteristics of left- and right-brain thinking, Betty Edwards says that the left brain is verbal, using words to name, describe and define, while the right brain is nonverbal, has an awareness of things, but minimally connects with words.
