Home Page || The Calvin Bookshelf || Science Surf magazine || Table of Contents
A book by
William H. Calvin
The Throwing Madonna
Essays on the Brain
Copyright 1983, 1991 by William H. Calvin.

You may download this for personal reading but may not redistribute or archive without permission (exception: teachers should feel free to print out a chapter and photocopy it for students).

Scanned, OCR'ed, and webbed -- but NOT proofread (14 Jan 97)


Left Brain, Right Brain:
Science or the New Phrenology?

If the Lord Almighty had consulted me before embarking on the Creation, I should have recommended something simpler.
ALFONSO X, King of Castile (1226--1284)

Make it thy business to know thyself, which is the most difficult lesson in the world.

Left, right, left, right--the marching song of the two-mind movement. To hear them talk, you'd think that everyone had a second mind, suppressed by the first. That the vocal left brain dominated the poor artistic right brain. Preventing it from getting a creative thought in edgewise. Soon there will be a consciousness raising movement: Stop referring to the left cerebral hemisphere as the "dominant" one. Invent a more egalitarian term like co-chairperson. Co-chairhemisphere?
      Alas. Were cerebral physiology so simple! If there were strong dominating influences, it would make our research far easier. It is unfortunate that "dominance" is a word with two entirely different meanings, even within psychology. When talking about pecking order, dominant refers to an animal that usually wins in a one-on-one encounter, the animal that can approach, threaten, and successfully displace another animal from food, mates, or the best nesting place. In talking about the cerebral hemispheres, however, dominant is merely a shortening of the technical term "language-dominant hemisphere." It is the outcome of a test to find out where language lives in a person's brain, such as injecting anesthetics into the left and right carotid arteries and seeing when the patient stops talking (or the simpler, but not as accurate, test that merely involves having the subject look at a dot in the middle of a screen and then briefly flashing words to the left or right of the fixation point; people with left-brain language will have an easier time with right-sided words since the information goes first to left brain).
      Although a few percent of people have right brains that are language-dominant, about 93 percent of us use the left side. A few percent have "mixed dominance," where both sides are used for language (that is, injecting anesthetics on either side will interfere with speech). But the term hardly refers to language dominating art or music: it's just which side is more essential for language than the other.
      Shades of gray become black and white when the dichotomizers go into action. But the real problem is that most of the creativity arguments have about as much to do with the brain as does the English language. The structure of the brain probably has a lot to do with the capability for, even the "deep structure" of, language--but brains hardly come in Chinese, Swahili, and English flavors. Like English per se, the creativity and holistic thinking influences probably lie more in the realm of culture than brain structure. And hardly on a particular side of the brain.
      A few decades ago, similar suppressed-creativity arguments were floating around. It's just that they were then phrased in terms of contemplative Eastern thought versus authoritarian Western religious influences. More recently, the dichotomous rendition was holistic versus linear thinking. And now the mod metaphor is right brain versus left brain. Except that it is the worst of mixed metaphors, the kind that mixes up metaphor with reality.
      Being a neurophysiologist, I suppose I ought to feel that progress has been made: in no other age could it have taken a mere twenty years to shift from a predominantly religious metaphor to a semi-scientific one. But the neurophysiologists and neuropsychologists who specialize in the human cerebral cortex are starting to view the left-righters with something of the wariness which the astronomers reserve for astrology.
      In one sense, the picture of the mind painted by the leftrighters is rather like one of those magazine illustrations of the human brain and its convoluted surface--one feels quite sure that the artist has never seen a real human brain, either a fresh one or a preserved one. The result of embroidering upon another artist's rendition bears even less fidelity to the original, an artistic version of the spread of a rumor. My favorite painting of the brain's convoluted surface is not the usual gray modeling-clay rendition but a red and purple rising-sun sphere whose "convolutions" come close to looking like the cracks in a parched mud flat. (It is my favorite only because it's on the cover of a paperback called Inside the Brain by Calvin and Ojemann; our publishers carefully avoided showing it to us until after the press run.)
      If you try tracing some of the left-righter enthusiasms back to the scientific evidence, you'll often wonder how the rumor even got started. It is not that the scientific evidence contradicts their notions, though that sometimes happens. But they've gotten way out in front of the state of the scientific art, in about the way the phrenologists' maps (all those political subdivisions on the brain map marked love, acquisitiveness, compassion, etc.) were premature, quite unsupported by any evidence at the time. Indeed, one has the suspicion that the nineteenth-century parlor game aspect of phrenology resulted in pinning functions onto a brain map, like pinning the tail on the donkey while blindfolded. The left-righters' notions may have a base in a laudable know thyself effort, but their standards for evidence can sometimes be subservient to their aesthetic enthusiasms ("a nice symmetrical arrangement, isn't this?"). To know thyself may be the most difficult of lessons; to know the brain is surely one of the most challenging of the sciences, one that does not lend itself to easy labels.
      Besides the usual human tendency to see things as either this or that, the dichotomizers' view of cerebral physiology tends to be biased by the special case of language. Language in the human brain is almost totally located in one cerebral hemisphere. For every fourteen people suffering language difficulties after a stroke near the Sylvian fissure, only one will have suffered right-hemisphere damage. This 13 to 1 lateralization ratio for language is the strongest deviation from the usual vertebrate brain plan of about 1 to 1, namely doing most things pretty equally in the two halves of the brain.
      But nothing else has such odds. Take visual and spatial relationships, the function most often assigned to the right-brain convolutions opposite those occupied by language in left brain. While there is indeed a specialized area used for recognizing whether a friend's face is happy or sad located just above the right ear, most visual-spatial functions are not exclusive to the right brain. A common one impaired by strokes is the ability to put things back together again--to reassemble the parts of a disassembled flashlight or toaster. Right-side damage causes such "construction apraxias" only about twice as often as comparable left-brain damage. The chances are about the same that map-reading will be impaired. Dressing apraxias, a conceptual inability to match up sleeves with arms when getting dressed, is five times more common on the right. Odds like 2 to 1, or even 5 to 1, are a far cry from language's strong 13 to 1 lateralization ratio. Thus it isn't left or right but both left and right in varying ratios for different functions.
      How do we find out? Our most detailed maps come not from stroke victims but from epileptics who are awake and talking while a neurosurgeon studies their brain, prior to removing the region which is starting the seizures. But we never get the chance to study both sides of the brain at the same time in the same patient (no, contrary to the imagination of magazine illustrators, neurosurgeons do not just lift off the top of the head like a skullcap; they're very selective and make an opening overlying the problem area--on one side). Until the blood-flow and metabolic nonsurgical techniques become more sophisticated, we will continue to have difficulty determining the maps of an individual's left and right hemispheres, estimating the extent to which one side of the brain can outperform (i.e., "dominate") the other in generating a particular human ability.
      But, the neurophysiologist objects, functionally everything may be all mixed up in a working brain. How can you know what the right brain is capable of by itself, on its own? Simple. As every reader of pop psychology now knows, just cut the corpus callosum which connects the left and right cerebral cortex. Et voila, the split brain, isolating the two minds and all that. These studies, which won a Nobel Prize in 1981 for Roger Sperry, have caught the eye of a public that is fascinated by Dr. Jekyll and Mr. Hyde split-personality stories. Not that any of the split-brain patients have anything dramatic along that line, it's just that their right hand doesn't always approve of what their left hand is doing.
      Interpreting the result is far harder than doing the surgery, as the original investigators have noted. Take, for example, the suggestion that the right brain has its own simple language center (some split-brain patients can spell out simple words with their left hand, controlled by the right brain). Many neuroscientists familiar with the childhood plasticity of the brain have worried that the split-brain patients might be highly atypical of humans in general, that some of their left-brain functions might have moved over into their right brain during childhood. That happens to young children after a severe injury to the left brain (though, as millions of aphasic adults testify, it is an ability lost with age, probably mostly confined to the preschool years), and perhaps it happens in a child with severe epilepsy. Indeed, nearly all of the split-brain patients had their epilepsy from an early age. Unlike the epileptic operated upon in the more traditional brain-mapping cases, the split-brain candidate usually has seizures originating from a whole cerebral hemisphere rather than one small piece of it. One way to try to avoid taking out the whole bad hemisphere is to just cut its connections to the good hemisphere, which was the surgical rationale for the splitting of the corpus callosum. Thus split-brain patients may be excellent candidates for studying the ability of functions to migrate from one hemisphere to the other during early childhood, rather than excellent candidates for inferring the separate abilities of the two hemispheres.
      Details! Just give me the big picture--isn't that language on the left, visual-spatial imagery on the right? And isn't language all tied up with sequential things, narrowly focused cause-and-effect reasoning? And isn't the right brain better at holistic, seeing-the-big-picture sorts of things? Why not talk about two minds?
      Maybe. But we must be careful to distinguish the interesting questions from the factual answers. In science, one tries to phrase questions narrowly and carefully, then gather the data so as to force nature to yield up unequivocal answers. We are just getting started at asking productive questions. We are just acquiring some of the needed tools, though they are still quite inadequate to satisfy our appetites for knowledge.
      And while neuropsychology and neurophysiology struggle along trying to get firmer answers on shrinking research budgets, the left-righters are happily charging ahead full steam, prematurely assigning functions to left and right brain with all the enthusiasm of nineteenth-century phrenologists. Nowadays, one cannot even publish a drawing techniques book without invoking the liberation of the repressed right brain. I'm told that it's even a good drawing book, but its best-seller status is probably due to its gimmick of borrowing a quasi-scientific foundation. And it was a most successful gimmick at that--the taxes paid on the take from Drawing on the Right Side of the Brain and its many imitators probably exceed the world's neuropsychology research budgets.
      Now perhaps that's the way to finance our research in the starvation-budgets era! We researchers can get together and write (unscientifically and anonymously, of course) a really splendid right-brain best-seller. Perhaps a marriage manual, showing how a right-brain type can achieve compatibility with a left-brain type? Or maybe a cat book for right-brain people? No, I've got it-- Cooking on the Right Side of the Brain! We'll locate cooking skills on the right-brain map just above the right nostril. And we won't let the cook add together the ingredients in the usual sequential way-- which is, of course, a left-brain way of mixing. An obvious no-no. After all, the ingredients care with whom they mingle, who's in the bowl already when they arrive. Instead, we'll have the cook dump all of the ingredients into the mixing bowl simultaneously, in a great splashy, holistic, rightbrain moment of truth!

The Throwing Madonna:
Essays on the Brain
(McGraw-Hill 1983, Bantam 1991) is a group of 17 essays: The Throwing Madonna; The Lovable Cat: Mimicry Strikes Again; Woman the Toolmaker? Did Throwing Stones Lead to Bigger Brains? The Ratchets of Social Evolution; The Computer as Metaphor in Neurobiology; Last Year in Jerusalem; Computing Without Nerve Impulses; Aplysia, the Hare of the Ocean; Left Brain, Right Brain: Science or the New Phrenology? What to Do About Tic Douloureux; The Woodrow Wilson Story; Thinking Clearly About Schizophrenia; Of Cancer Pain, Magic Bullets, and Humor; Linguistics and the Brain's Buffer; Probing Language Cortex: The Second Wave; and The Creation Myth, Updated: A Scenario for Humankind. Note that my throwing theory for language origins (last 3 essays) has nothing to do with the title essay: THE THROWING MADONNA is a parody (involving maternal heartbeat sounds!) on the typically-male theories of handedness.
Many libraries have it (try the OCLC on-line listing, which cryptically shows the libraries that own a copy), and used bookstores may have either the 1983 or the 1991 edition.

Email || Home Page || The Calvin Bookshelf || Table of Contents || End notes for this chapter || Continue to read next chapter