Half and Half

The brain's sides have a relationship. Like most, it's complicated.


in Archive


Back in junior high school health class, we were told that the brain
has two different hemispheres — the left and the right. The left brain,
the textbook stated, is responsible for language, math, and science,
logic and rationality. The right brain was the artistic one, the
creative half of the brain. But that’s not quite true. Neuroimaging and
experiments on patients with split brains and brain damage to only one
hemisphere have allowed a much more detailed, and fascinating,
accounting of how the two parts interact with the world, and how they
combine to become a unified consciousness (and, in some cases of mental
disorders, how they occasionally don’t). Iain McGilchrist has combined
scientific research with cultural history in his new book The Master and His Emissary: The Divided Brain and the Making of the Western World to
examine how the evolution of the brain influenced our society, and how
the current make up of the brain shapes art, politics, and science, as
well as the rise of mental illness in our time — in particular
schizophrenia, anorexia, and autism.

  • The Master and His Emissary: The Divided Brain and the Making of the Western World by Iai McGilchrist. 608 pages. Yale University Press. $38.00.

That eighth-grade level science textbook was kind of correct. While the left brain does contain much of the language center of the brain, a person cannot understand context without the right hemisphere. Metaphor, irony, and humor are all processed by the right brain. When engaging in face-to-face conversation, it processes facial expressions to add depth to the meaning. Most activities, from painting to mathematics, are processed by both the left and the right hemispheres of the brain. The differences between them have to be defined in a different way. The left brain brings precision, focus, abstraction, rationality, and fixity. The right brain has a more open view of the world. It provides context, whether finding humor in a punch line or bringing a sense of history to a question posed to it. In a healthy, functioning brain, the right hemisphere sends information about a situation to the left hemisphere, which “unpacks” the information using its tools to find clarity, and then it vocalizes the response, either in thought or expression.

When we look at unhealthy, nonfunctional brains, however, the two halves become much more complex. Patients with only one fully functioning hemisphere or those who have had their corpus callosum (the area that bridges the two hemispheres) severed — either because of injury or as a way to treat debilitating seizures — tell us a lot about the personalities of the two hemispheres. And they do have personalities. When presented with a illogical scenario, the left brain creates logical black holes to convince itself and others it is correct, and it is so swayed by authority that it refuses to correct obvious wrongs. People who only have functioning right hemispheres might have less access to rational thought, but when Russian scientists tell them that a porcupine is a monkey (an actual study cited in The Master and His Emissary), they don’t believe it’s true. People using only their left hemispheres do. They also refuse, or may actually be unable, to admit they are wrong. They are overly confident of their abilities and intelligence, and they can justify nearly everything to themselves by creating strings of false logic. (As in, monkeys climb trees. Porcupines climb trees. A porcupine must be a monkey.)

Another example of this complexity is the way a person’s relationship to his body changes with damage to the right hemisphere. People who have suffered a stroke will often have disabilities on the opposite sides of their bodies. When the right hemisphere is left intact, it acknowledges the damage and almost obsesses over it. The left hemisphere will disown a weakened left arm or leg, to the point of believing that the real arm, according to a woman who had a right brain stroke and is quoted by McGilchrist, is hiding “under the bedclothes” and this arm attached to her body “is my mother’s. Feel, it’s warmer than mine.” Other patients with similar damage report that their body parts have been replaced with wood, or they will simply not admit they are disabled. When presented with the proof, their twisted limb held up for them to see, the patient will turn his head or close his eyes.

For a long time, the left brain has been viewed as being the dominant, more highly evolved, more useful part of the brain, possibly because, as McGilchrist says, we are “trapped inside a culture that is so language-determined.” We think in language, and with the advent of e-mail and text messaging we communicate in written language more than ever before. The right brain may communicate to us through intuition, but we can, and do, often override that with logic. For a long time it was believed that the corpus callosum’s primary focus was the communication between hemispheres. While that is partially true, most of what it does is allow one hemisphere to inhibit the other. This is primarily so that both hemispheres do not attempt to perform the same task (a problem you frequently see in patients with severed corpus callosums — more on that in a minute), but it can also mean that a hemisphere that is not suited for a task can “claim” it anyway, and inhibit the proper hemisphere from contributing. Which hemisphere dominates more tasks than the other can vary from person to person — there are a multitude of horrible online quizzes that will tell you which hemisphere rules your decision making processes — but on a larger scale, you see a pattern forming with certain cultures and with variations depending on where humans have been in their evolutionary history.

Watching experiments with split brain patients from the 1970s, you’ll see scientists referring to the right brain as the “silent” and “feminine” side of the brain. It deals with emotions and empathy, and all of that useless stuff. But in reality, McGilchrist reports that patients with damage to their left hemisphere — even to the point of removing the entire hemisphere and with it their ability to communicate with language, and even sign language — actually function better in the world than those with right hemisphere damage. It’s not just scientists, but artists, writers, philosophers, religious leaders, and politicians who have created an environment in which the right brain is seen as being weak, and left brain concepts and systems are viewed as being the ideal: logic over intuition, the pursuit of money over community, brain over body, industry over nature. This devaluing of the contributions of the right brain has created a shift in the way we interact with the world. We have created a society that is completely reliant on the left hemisphere, on logic and materialism and abstraction, and in doing so we have created what McGilchrist calls “the predominantly left-hemisphere phenomenon of a competitive, specialised, and compartmentalised world.”

It’s difficult not to agree that right brain territory has been hijacked by the left brain. Visual art is dominated with abstraction and shocking imagery. (The left brain, hungry for stimulation, prefers the shocking and the novel to the beautiful.) Religion has seen the rise of the super-rational atheist movement while spirituality has been overrun by materialism, another abstract left brain concept. The Secret would have you believe that the entire purpose of divinity is to make you rich and thin, and even the evangelists preach that Jesus wants you to have that nice house in the suburbs. Social anxiety disorder would seem to be the domain of the left brain, completely unable to read social cues, trying to interact with other people. It overthinks things, misreads situations, and creates awkwardness by being too self-aware and not letting the right hemisphere do what it does best.

Every age has its own range of mental disorders. We don’t suffer much from hysteria anymore, just like we don’t hear of the Victorians battling autism as we now do. Some of that is just diagnosis: There may have been autistic men and women in the world before today, but they may have been called something else. McGilchrist, in consensus with many psychiatric historians, believes our society creates specific mental illnesses. McGilchrist just takes it a little further, believing it is how the brain of that age functions that defines its dysfunctions. The way we receive information, the language we use, the environment in which we live, the values of our culture — all of these things influence the way we use our brains, and this creates a feedback from the culture back to the brain. Certain eras, such as the Romantic period, praised nature and held ideals about love and beauty and wrote poetry. As a result, the right brain was much more active, and the reigning disorder of the day was melancholia, a problem of the right brain.

Our contemporary culture, with its loneliness and its materialism and disjointed nature, is typical of left brain dominance. As such, we have autism, which is an almost total dysfunction of the right brain: an inability to read facial expressions, a lack of empathy, failure to recognize metaphor or irony. Schizophrenia is a disorder where logic runs mad. Faulty connections are made, false conclusions drawn, and yet the disordered cannot release themselves from the grip of the delusion because to them it makes perfectly logical sense. Anorexia is a hatred, a mistrust, and a warping of the image of the body. These are left-hemisphere ways of thinking taken to their extreme, and never in the history of mankind have we been afflicted with disorders quite like these. Consider them warning signs, if you will, about what could lay ahead if progress continues in this direction.

But McGilchrist believes the pattern of the evolution of the human brain is circular. Domination of one hemisphere will be checked by the growth of the neglected hemisphere. Life with a dominant right brain is not much better, unless mass suicide inspired by a romantic Goethe novel is your thing. The ideal is the harmonious workings of both hemispheres, as life appeared to be in pre-Socratic Athens. In that time, strides were made in drama and poetry in the right hemisphere, and philosophy and the written language in the left. There are signs we could swing that way again, with most of the scientific advances being made in the very uncertain, quite illogical realm of quantum physics. The left brain hates uncertainty, and while it may be true that you can know where a particle is located or how fast it is moving, but not both at the same time, it doesn’t make sense. There’s a reason why scientists like Wolfgang Pauli made breakthroughs in the quantum field due to visions and dreams — it’s processing done by the right hemisphere, because it warps the boundaries of the scientific method. The advances in neuroimaging can also lead us back to our belief in the power of the right hemisphere as we can now see it at work when we can’t hear it. It is not the weaker half — in fact it possesses what we think of first when we are listing the things that separate us from animals: empathy, art, humor, culture, and wisdom. • 21 December 2009