LEFT BRAIN vs RIGHT BRAIN
More than a century, we’ve known the brain’s two sides serve different functions. Accidents, strokes, and tumors in the left hemisphere generally impair activities of the rational, verbal, nonintuitive mind, such as reading, writing, speaking, arithmetic reasoning, and understanding. Similar lesions in right hemisphere seldom have such dramatic effects.
By 1960 the left hemisphere (or “left brain”) was well accepted as the dominant or major hemisphere, and its quieter companion as the subordinate or minor hemisphere. The left hemisphere is rather like the moon’s facing side—the one easiest to observe and study. It talks to us. The other side is there, of course, but hidden.
When surgeons first separated the brain’s hemispheres as a treatment for severe epilepsy, they effectively created a small population of what have been called the most fascinating people on earth—split-brain people who are literally of two minds. The peculiar nature of our visual wiring enables researchers to send information to either the patients’s left or right brain by having the patient stare at a spot and then flashing a stimulus to the right or left of it. (They could do this with you, too, but in your intact brain the telltale hemisphere that received the information would instantly call the news to its partner across the valley. Split-brain surgery severs the phone cables—the corpus collosum—across the valley.) Finally, the researchers quiz each hemisphere separately.
In an early experiment, psychologist Michael Gazzaniga asked split-brain patients to stare at a dot as he flashed HE•ART. Thus HE appeared in their left visual field (which transmits to the right brain) and ART in the right field (which transmits to the left brain). When he then asked them what they had seen, the patients said they saw ART and so were startled when their left hands (controlled by the right brain) pointed to HE. Given an opportunity to express itself, each hemisphere reported only what it had seen. The left hand intuitively knew what it could not verbally report.
Similarly, when a picture of a spoon was flashed to their right brain, the patients could not say what they saw. But when asked to identify what they had seen by feeling an assortment of hidden objects with their left hands, they readily selected the spoon. If the experimenter said, “Right!” the patient might reply, “What? Right? How could I possibly pick out the right object when I don’t know what I saw?” It is, of course, the left brain doing the talking here, bewildered by what it’s nonverbal right brain quietly knows.
These experiments demonstrate that the right brain understands simple requests and easily perceives objects. In fact, the right brain is superior to the left at copying drawings, recognizing faces, perceiving differences, sensing and expressing emotion.
Although the left brain is adept at literal interpretations of language, the right brain excels in making subtle inferences. If “primed” with the flashed word foot, the left brain will be especially quick to then recognize the closely associated word heel. But if primed with foot, cry, and glass, the right brain will more quickly recognize another word that is distantly related to all three: cut. And if given a verbal problem—what word goes with high, district, and house?—the right brain more quickly than the left recognizes that the solution is school. As one patient explained after suffering right-brain stroke damage, “I understand words, but I’m missing the subtleties.” Thus, the right brain helps us modulate our speech to make meaning clear—as when we ask “What’s that in the road ahead?” instead of “What’s that in the road, a head?”
Some split-brain surgery patients have temporarily been bothered by the unruly independence of their left hand, which might unbutton a shirt while the right hand buttoned it, or put groceries back on the shelf after the right hand put them in the cart. It was as if each hemisphere was thinking “I’ve half a mind to wear my green (blue) shirt today.” Indeed, said Nobel laureate psychologist Roger Sperry, split-brain surgery leaves people “with two separate minds.” (Reading these reports, I imagine a split-brain person enjoying a solitary game of “rock, paper, and scissors”—left hand versus right.)
When the two minds are at odds, the left brain acts as the brain’s press agent, doing mental gymnastics to rationalize unexplained action. If the right brain commands an action, the left brain will intuitively justify it. If the right brain is commanded to laugh, the patient will respond with laughter. The left brain, when asked why the laughter, will rationalize, perhaps pointing to the “funny research.” If a patient follows an order sent to the right brain (“Walk”), the left brain will offer a ready explanation (“I’m going into the house to get a Coke”). Michael Gazzaniga concludes that the left brain is an “interpreter” that instantly constructs theories to justify our behavior. We humans have a quick facility for constructing meaning.
Most of the body’s paired organs—kidneys, lungs, breasts—perform identical functions, providing a backup should one side fail. Not so the brain’s two halves. They are a biological odd couple, serving differing functions, each seemingly with a mind of its own. From simply looking at the similarly shaped hemispheres, who would suppose that they contribute uniquely to the harmony of the whole?
And not even Freud (who didn’t anticipate the cool intelligence of the hidden mind) could have supposed that our brains are humming with so much resourceful activity outside our conscious awareness, and that our interpretive left brain, grasping at straws, can so speedily intuit false explanations for our behavior. Beneath the surface there is much intelligence, and above the surface there is much self-delusion.