Leonardo's Brain

by Leonard Shlain

  It is during the phase of perspiration, and sometimes when the active phase of seeking a solution is over, that the most mysterious aspect of creativity commences—that of incubation. Somehow, even though the left brain is no longer concentrating on the problem, at some deep, subterranean level, the right brain continues to labor. Many times in art and science, the search for the answer to a particularly vexing problem eludes the laser-concentrating ability of the left hemisphere. Despite the sustained application of all the forces of one’s logic, the problem remains. And then, in a moment of relaxation or when the artist or scientist is doing or thinking about something entirely unrelated, the answer suddenly pops into consciousness.

  The French mathematician Henri Poincaré described how the answer to a complex mathematical problem eluded him despite his most concentrated efforts. Then he put the problem aside and went on holiday. Several days later, when he was boarding a bus, as he placed his foot on the step, the solution occurred to him as if from out of the blue.

  There is a common saying in science that the bed, the bath, and the bus are the three most inspirational locations to have major insights. Ideas emerge into consciousness as if from out of nowhere. Illumination occurs in the most mundane places, and when we are going about the most ordinary tasks. Typically, a solution to a problem will burst upon us when we are not thinking about it. If this is the case, how, and where, does the brain pull off its rabbit-out-of-a-hat trick?

  Think of the right and left hemispheres as Siamese twins joined at the corpus callosum. Although each hemisphere has its own preferences and approaches, each contributes to make a whole person only when the corpus callosum integrates the two. But in the process of generating a major creative insight, a disconnect must occur between the two halves. Arthur Koestler called this “hemispheric bisociation.”

  The two hemispheres work in concert nearly all of the time, and the dominant hemisphere has the capability to inhibit the nondominant hemisphere. Natural Selection gave the left hemisphere hegemony over the right. Under certain circumstances, however, the minor hemisphere must escape the control of the major one to produce its most outstanding contribution—creativity. For creativity to manifest itself, the right brain must free itself from the deadening hand of the inhibitory left brain and do its work, unimpeded and in private Like radicals plotting a revolution, they must work in secret out of the range of the left hemisphere’s conservatives.

  After working out many of the kinks in the darkness of the right hemisphere’s subterranean processes, the idea, play, painting, theory, formula, or poetic metaphor surfaces exuberantly, as if from beneath a manhole cover that was overlaying the unconscious, and demands the attention of the left brain. Startled, the other side responds in wonderment.

  Numerous artists and scientists throughout history have experienced this strange phenomenon. If creativity begins in the right brain, it must at some point make the journey across the great divide between the two hemispheres. To translate an insight into words or action, the left hemisphere must be involved—but not always. In the kinesthetic arts, such as dance or basketball, the right brain may invent a creative maneuver never used by anyone before. In general, however, the left lobe must translate the insight into words, or verify the insight using paint or equations. This step requires that the insight be formally introduced to the left lobe.

  After arising in isolation in the right hemisphere, the creative insight must find a way to be ferried across to the left side of the brain. This is done by way of the corpus callosum, that broad band of neurons that connects the right and left cerebral hemispheres. Is it merely a conduit, or does it serve a higher, more integrative function?

  The corpus callosum is the most poorly understood structure in the human brain, and it also happens to be the largest. Arching over the midline, the corpus callosum is an enormous band of well over 200 million neurons. Neuroscientists have two theories as to the function of this broad band of connecting fibers: The first posits that the corpus callosum serves only as a conduit that allows the right hand to know what the left hand is doing, and vice versa. The opposing theory proposes that the corpus callosum integrates information from each side, functioning as a third brain, producing something qualitatively different from what the right and left brain generate individually.

  Because creativity depends to a large extent on the message of the right brain making it over to the left brain, ungarbled, the maturation schedule of the corpus callosum is pertinent. Myelin is a gigantic molecule that binds fat globules within a lattice of protein. Once formed, it serves to sheath individual neurons, the information-transmitting cells of the nervous system. Myelination is the process by which a human brain’s nerves receive their myelin coatings, the function of which is similar to the insulation used on copper wires. Disparate areas of the brain and the peripheral nervous system myelinate at different ages during growth.

  Both nerves and wires conduct electrical currents that generate electromagnetic fields, extending into the surrounding space. As with man-made devices such as radio and television transmitters, “interference” (or static) in nerves is a potential problem. To protect signals from corruption by neighboring electromagnetic fields, each individual nerve is encased in insulating material.

  In the electrical industry, this substance is the familiar plastic or rubber that sheaths the wires of appliances. In the brain and peripheral nervous system, the insulating substance is myelin. The fetal brain contains very little myelin. Evidence of a newborn’s lack of it is apparent in the Moro reflex. Hands clapped loudly near a newborn will startle it. The sharp sound sets off a chain reaction, so that the infant responds as if every nerve in its body had been activated. The newborn adopts a signature open-armed grasping manner, as if the child were reaching out to embrace its mother for protection.

  As an infant’s brain grows, it steadily lays down myelin around its nerves. In general, myelination proceeds from the bottom up, back to front, and right to left, and takes some twenty-odd years to complete. Myelination of the corpus callosum begins at the age of three months but is not complete until early adulthood. This is the reason why neuroscientists suspect that creativity does not really peak until late adolescence or early adulthood. There are exceptions to this rule, as Mozart and other child prodigies have demonstrated.

  This brings us back to the wiring diagram in Leonardo’s brain. How did Leonardo’s left-handedness and ambidextrousness affect the balance of his left brain and his right brain, or, should we say, his balanced brain?

  Chapter 10

  Fear, Lust, and Beauty

  Lust is the cause of generation. . . . Beauty in life perishes, not in art.

  —Leonardo da Vinci

  [Leonardo’s art is an] interfusion of the extremes of beauty and terror.

  —Walter Pater

  When John Keats penned his immortal line of poetry in “Ode on a Grecian Urn”—“Beauty is truth, truth beauty—that is all Ye know on earth, and all ye need to know”—he could not have more succinctly described the twin goals to which Leonardo dedicated his life. The Florentine polymath spent enormous time, study, and effort attempting to discern the truth behind natural phenomena. He then employed his artistry to depict those truths in a way that continues to captivate and enthrall five hundred years later. In his mature years, he sought to uncover the principles that lie beneath it all.

  In seeking the function of the human eye and dissecting it with unerring accuracy, in noting how atmospheric conditions affect the view of distant objects, or drawing a mechanical device with great accuracy and detail, Leonardo illuminated his search for truth using his art. But his greatest fame rests with his unique ability to translate truth into beauty, to capture the delicate emotions in a child’s face, a woman’s smile, an anguished combatant with an unsurpassed skill.

  What are the origins of our need to appreciate beauty and satisfy our insatiable curiosity concerning truth? Many poets, art critics, philosophers, and commentator
s from other academic fields have weighed in on this subject and tried to define these two abstract words. Homo Aestheticus: Where Art Comes From and Why is a book written by Ellen Dissanayake that attempts to identify the sources of beauty. Although deeply informative, quoting many art critics, psychoanalysts, and evolutionists, the book does not delve deep enough to answer the question: Why are we blessed with the aesthetic sense?

  I want to approach the problem from an evolutionary point of view. Why did we humans evolve an aesthetic sense so sensitive that we can make a judgment about good and bad art? Why is discovering the truth at the heart of matters such an obsession with us?

  Humans are qualitatively different from all other animals. Among the many features that we are quick to list to advance our claim of superiority are textured morality, complex language, and sophisticated toolmaking. Recently, however, biologists have increasingly identified other species that manifest similar behavior. Much of our “uniqueness” has been reclassified to be more a matter of degree than one of distinction.

  Armed with mounting evidence, researchers in the relatively new field of sociobiology posit that human characteristics, originally thought to be God-given, can be explained in terms of Natural Selection—­random mutations that ensure humans will be able to compete with other species for resources. There remain some features, however, that as best as we can ascertain, seem relatively unique to humans. Foremost is our creativity.

  At the heart of all creativity lies our fear of danger. Natural Selection installed this basic instinct in every animate creature to enable the creature to stay alive. Among all animals, it is the premier early-warning system. The key to sensing trouble is any alteration in the environment. The sudden appearance of novelty alerts an animal that something is awry, and its first imperative is to make sure that the “something” is not hankering to eat it.

  Upon the sudden appearance of novelty in the environment, a carefully orchestrated cascade of neurotransmitters begins its waterfall of changes that will alter an animal’s state of consciousness. The arousal center in the brain shifts from the wide-focus diffuse lens and immediately lasers at the source of the novelty, effectively shutting down extraneous input. It must devote all its concentration to the narrow cone of vision that is now scrutinizing this one aspect that has captured its attention.

  The flood of danger hormones released by the pituitary activates the release of adrenaline from the adrenal glands. (The technical name for adrenaline is epinephrine.) This puts the animal in a state of maximal hyperalertness, preparing it to fend off a potential threat. Not coincidentally, this is also the state that artists and scientists both report that they are in when they are experiencing a major insight. A heightened alertness, a burst of energy, and an increased clarity of thought are common to both fear and creativity. In addition to adrenaline, the danger hormones from the pituitary urge the adrenal glands to increase their production of corticosteroids, further preparing the body for whatever comes its way. Steroids bulk up the muscle, improve the immune system, and help blood to clot faster.

  In almost all other animals, because threats originate equally from the right and left sides, the midline brain structures that include the amygdala and hypothalamus can be counted on to generate an equal response to danger. Not so in the human animal. The right side of the hippocampus is activated in dire circumstances, and the left side is relatively unsupportive. The right side of the hypothalamus plays a greater role in priming the pump of the pituitary than does the left. The right brain has a larger concentration of norepinephrine, the danger hormone, than the left.

  Not all novel situations result in danger. To prevent the nervous system from constantly being thrown into a state of heightened receptivity, Natural Selection installed the counterreaction called “habituation.” The first time a novel situation occurs, the internal response of the animal resembles a four-alarm fire. However, if no threat to life or limb materializes, then the next time it will evoke a lesser emotion of fear. Finally, when the organism is habituated to it because it is deemed not a threat, the fear response will shut down.

  As an example, in the history of science, this condition of habituation can be understood from the insights of Thomas Kuhn in his classic book, The Structure of Scientific Revolutions. Kuhn’s thought would suggest that scientists, before the breakthroughs of a revolutionary thinker on the order of Einstein or Newton, had become “habituated” to the kind of thinking that had characterized their respective fields. Once the revolutionary ideas were brought forth and all that they had taken for granted had been overthrown, there was an initial period of shock and disbelief. Rejection of the new paradigm was the order of the day, because their habituation to what they had become accustomed to was so strong.

  Novelty is the crux of creativity. For those who “get it,” there is wonderment and great surprise, an emotion commonly witnessed in animals (and humans) when they are suddenly confronted with danger. The emotions associated with creativity are all closely related to the appreciation of danger. Excitement serves to get the nervous system ready for approaching danger, and it is the same heightened state of emotions experienced by someone who has a new idea. Before he painted Les Demoiselles d’Avignon, Picasso was visiting the Trocadero when he came upon the primitive masks from Africa. He began to shake with anxiety, the same emotion that humans experience when confronting fear.

  Internally, the rush of adrenaline that accompanies the presence of danger is indistinguishable from that which floods the nervous system at the eureka moment. It is not uncommon for someone possessed of a really great idea to slam his or her fist against an open palm, strike a wall, or make an extreme physical gesture. The metaphors used to preface an insight are revealing. “I ‘hit’ upon a ‘shocking’ idea.” “A great thought ‘struck’ me.” “I was ‘knocked’ out by it.” “I had a ‘dynamite’ idea.” “I was bowled over.” And, “I really slammed it right out of the park.”

  Creativity is a combination of courage and inventiveness. One without the other would be useless. The courage of Leonardo to use experience as his teacher rather than parrot what was written in ancient textbooks; the stance of a Giordano Bruno in promoting the Copernican theory that resulted in the Church burning him at the stake; and the hubris of the lowly twenty-six-year-old patent official submitting his paper on relativity without major references to a prestigious journal are all examples of courage.

  Because of the lopsided shift to the left hemisphere of nearly all the language modules, the right side ended up with an equally lopsided share of the emotions. Fear plays a most prominent role. Because the right brain is essentially bereft of language, the description in words of how the creative process proceeds is practically impossible. Ask artists or scientists how they arrived at their most novel and creative work, and you will no doubt receive either an inarticulate answer or the left brain’s confabulation.

  A few higher animals are capable of creative solutions to problems. But, as best as we can determine, none of their solutions include an aesthetic quality. That sense remains among the most resistant to the sociobiologist’s evolutionary explanations. A Pleistocene hominid lost in the contemplation of a beautiful sunset would be less alert, making him an easier target for a predator on the prowl. It is not at all apparent why an expenditure of considerable time and calories of energy creating a work of art that is nonutilitarian, and whose sole purpose is to make something that is pleasing to the eye, would increase the fitness, either physical or reproductive, of the species.

  There are suggestive examples of this trait existing among a few animals, but a fully developed sense of beauty seems to have blossomed in humans to a far more sophisticated degree than in any other animal. Which leads to the question: From an evolutionary point of view, why are the genes that enable this trait sitting in our genome? And under what evolutionary pressure did they arrive in the first place?

  Despite the fact that different cultures may have wildly disparate conceptions
concerning what is beautiful, an appreciation of beauty seems to be universally distributed among peoples everywhere. And its distribution in any given population of humans seems to follow a bell-shaped curve: Some at one end are seemingly devoid of a sense of beauty, and others at the opposite extreme are exquisitely sensitive. At its core, a sense of beauty does not seem to be rooted in culture, but rather appears to be a quality that we are born with and refine as we grow older. As the German philosopher Immanuel Kant would say, it is an a priori potential that is built into our nervous systems.

  Examining the question of beauty is particularly relevant to a study of Leonardo. The Florentine master was extremely interested in ferreting out the elements of beauty to better represent them visually.

  Many philosophers, aestheticians, artists, and art critics have had an enduring interest in understanding what they think beauty is and what it is not. In contrast, although scientists consider the natural world to be a fit subject for investigation, examining what exactly is the scientific basis for our human sense of beauty has aroused remarkably little interest. This is all the more puzzling when one considers how often scientists wax rhapsodic in their memoirs about how they were moved to ecstasy by an elegant solution to a problem, or the sense of wonder they experienced facing the mystery of their particular field. In general, curiosity about the roots of why we humans seem to have evolved a sense of beauty is considered by most scientists to be beyond their purview. And yet, I will contend that the search for beauty has played a crucial role in propelling our species away from all the others. I believe that a highly refined sense of beauty, when combined with the most primitive of instincts—fear—is the driving force behind human creativity.