Leonardo's Brain

by Leonard Shlain

  When people find it necessary to express in words an inner experience such as a dream, an emotion, or a complex feeling-state, they resort to a special form of speech called metaphor—a unique right-brain contribution to the left brain’s language capability.

  The word metaphor combines two Greek words—meta, which means “over and above,” and pherein, “to bear across.” Metaphors have multiple levels of meaning that are perceived simultaneously.

  We can describe, measure, and catalog the objective world with remarkable precision without resorting to metaphor. But to communicate an emotion or feeling-state, metaphors become necessary. To say one’s heart is “trapped in ice” or “soaring like a bird in flight” expresses the synergy between the right brain’s concrete images and the left brain’s abstract words. Metaphors beget poetry and are essential to the parables of religion and the wisdom of folktales. Metaphor’s cousins—similes, analogies, allegories, proverbs, and parables—each allow multiple means of interpreting a single set of words. Myths and dreams, both closely linked to metaphors, reside principally on the right side of the brain. Neurologists have identified right-handed, left-brain-dominant patients who have suffered a major left-lobe trauma that renders them nearly speechless but still allows them to recite poetry that they knew before their trauma.

  The most compelling combination of metaphor and image is art. Great visual art is authentic, nonlogical, and nondiscursive. The artist frequently uses visual metaphor to transport us to complex feeling-states, such as awe. When art metaphorically “bears” us “across and above,” there are no transitions. It is an all-at-once quantum jump. When this happens, we somehow know we are in the presence of great art.

  The same right-hemispheric area that enables us to recognize faces helps us to appreciate the subtleties of portraiture. Not only are the characteristics of visual art responsive to the right hemisphere’s abilities, but also the single most common image found in Western art is the representation of the human face. As further evidence for the placement of art to the right, neurologist Théophile Alajouanine describes a prominent painter who suffered an extensive left-brain stroke, rendering the artist aphasic:

  His artistic activity remains undisturbed; indeed, he has even accentuated the intensity and sharpness of his artistic realization, and it seems that in him the aphasic and the artist have lived together.

  Besides metaphor, the right brain can decipher the tone of the message. By listening carefully to the forms of speech while the left hemisphere is deciphering its content, the right hemisphere ferrets out hidden messages by interpreting inflection and nuance. It assesses the speaker’s posture, facial expression, and gesture. Just below conscious awareness, it registers pupil size and hand tremors. Because it is almost impossible to describe how the right side deciphers nonverbal language, most people refer to this skill as “intuition.”

  Damage to the right brain, especially the right temporal lobe, produces left hemineglect syndrome. Patients become unaware of their left side. Women adorn themselves and comb their hair only to their right, ignoring the messy appearance on their left side. They eat only from the left side of the plate. Men miss shaving the left side, and both sexes frequently do not insert their arm into their left sleeve. They will talk to you if you stand to their right side, but they ignore everything on the left side of the room.

  It is significant that lefties rarely suffer a right hemineglect syndrome. And no right-handers experience a similar syndrome when they suffer a stroke in their left brain. The hemineglect syndrome almost always occurs only on the left, because it affects the right brain of the person.

  Another major right-brain feature is its ability to appreciate music. Perhaps we can’t all define it, but each of us is quite sure we can distinguish music from noise. Music is another example of the ability of the right brain to process information in an all-at-once manner.

  During World War I, doctors observed many soldiers who had sustained traumatic injuries to their dominant left hemispheres and, as a result, could not speak a word. This select group could, however, sing many songs they’d known before they were injured. Alexander Luria, the Russian neurologist, reported the case of a composer who created his best work after he was rendered speechless by a massive stroke in his left hemisphere.

  Other notable examples of this division include French composer Maurice Ravel, who suffered a stroke in his left hemisphere that left him unable to speak, write, or read musical notation. Yet, he could sing and play on the piano from memory any piece he had learned before his stroke. Carl Orff, choirmaster of the famed Vienna Boys’ Choir, seems to have understood this dichotomy in brain function intuitively; he would not accept a child into his choir who had learned to read and write.

  Doreen Kimura convincingly demonstrated the separation of music and speech centers in the brain in experiments performed on commissurotomy patients. Examining patients who had had their corpus callosum divided in split-brain surgery, she had her researchers play a recording of a song and then ask the patient what they had heard. Their left brain could flatly repeat the lyrics of the song but could not hum its melody. The right brain could hum the melody but could not sing the lyrics. A conversation can be understood only when one person speaks at a time. One’s right brain can listen to the sounds of a seventy-piece orchestra and hear them holistically.

  On an MRI brain scan of someone devoid of musical training, the right parietal lobe lights up more than other areas when he or she is listening to music. If, however, he or she is a musician who plays only by ear, then the right-parietal and right-frontal lobe activates. If the individual has learned musical notation—a form of writing—then both areas continue to light up, but the left-parietal lobe will also show considerable activity.

  Another example of how speech and music are evenly distributed to either side of the brain is found in the research findings concerning prosody. Speech has two components: One is the content of speech, and the other is the manner in which it is spoken. Inflection, tone, and emphasis are all important clues regarding the interpretation of speech. The area in the right brain that is the mirror image of Broca’s area is responsible for adding this critical component to speech. How one says something can be almost as important, if not more important, than what one says. It lends an emotional tenor to language. Music is a function that resides principally in the right hemisphere. Orpheus, the poet-musician, holds court in the nondominant right side.

  The right brain processes being, images, metaphor, and music in a holistic manner and functions best in a visuospatial context, correlating parts to a whole while intuiting diverse relationships among them. The right side is better at appreciating spatial dimensions and judging distances. Driving, skiing, and dancing are its province. This side of the brain merges multiple determinants, multiple emotions, multiple meanings, multiple images, and multiple sounds into holistic states.

  The left brain’s primary functions are complementary to the right’s. While the right side manages the state of being, the left is primarily action oriented and concerned with doing. The left lobe controls the vital act of willing. Its agent, the right hand, picks berries, throws spears, and fashions tools. The trait that made us Homo faber, the toolmaker, depends on ordering a sequence of steps that exist in time.

  The left lobe knows the world through its unique form of symbolization—speech. Language is action oriented. Words are the very essence of the action mode; with them, we abstract, discriminate, analyze, and dissect the world. A vocabulary is the set of tools we use to do this.

  Whereas the right brain is the great synthesizer, left-brain analysis reduces everything to its component parts. This key left-brain task depends upon linear progression, in contrast to the holistic perception of the right brain. Abstract thinking is the ability to process information without resorting to images; it is the opposite of metaphorical thinking. Words substitute for images, and the mind can use these units of speech to build more complicated concepts. Simila
r to the way children assemble LEGOs, the mind arranges words as image substitutes, building concepts that allow us to think about freedom, economics, and destiny without needing to conjure up images for these words. Using language alone, the mind can rearrange these concepts and solve problems. To be able to leap from the particular and concrete to the general and abstract has allowed us to create art, logic, science, and philosophy.

  When humans went beyond thinking in pictures, they made a transformative evolutionary leap. Meaningless phonemes generated by the early humans’ larynxes became the words of speech and the tools of abstract thought. Later, when they combined the meaningless letters of alphabets or ideograms, they formed visual words to represent the world. In the process, they created the first abstract art form: the written word.

  Logic is not holistic. It click-clacks along the left brain’s linear railway of sequence. If–then syllogisms, the basis of logic, have become the most reliable method of foretelling the future. They have all but replaced omens, visions, and intuition. The rules of logic form the foundation of science, education, business, and military strategy.

  Along with doing, speech, and abstraction, the fourth characteristic unique to the left hemisphere is numeracy. Although the ability to count began in the visuospatial right brain, the ability to permutate larger numbers allows the left brain to build towering computations. The close association between abstract speech and abstract numeracy is evident among small children who learn the alphabet and learn to count at the same stage of development. Time and sequence are the very crux of the language of numbers; it is impossible to think of arithmetic outside its framework.

  All the innovative features of the left hemisphere—doing, speech, abstraction, and numbers—are linear. To develop craft, logic, strategy, and arithmetic, the mind must range back and forth along the line of past, present, and future. The survival and success of humans required that evolution set aside an area in the newly enlarging brain in which the concept of time could be contemplated free of the holistic spatial perceptions of the earlier mammalian and primate brains. The ability to fashion a tool with the right hand issues out of the left brain, and depends heavily on the ability to memorize a series of steps in sequence. The dominant hand is a specialized limb that is an extension of the sequential left hemisphere. An appreciation of linear time was the crucial precondition for linear speech. Sequence is the very crux of the language of numbers; indeed, a series of numbers is a sequence.

  The left hemisphere represents a radical new sense organ designed by evolution to perceive time. The left lobe processes time and keeps track of dates. Only humans can experience, or even understand, “birthdays.” It also can objectify the world. Instead of being part of nature, we can step back and see that nature is “over there.” And the left hemisphere is where we experience everything as separate from ourselves. We see trees as separate entities. If we go one level under the ground, we would see that all the trees are part of one gigantic organism, the forest. We’d see each tree is but an antenna for the organism and that all are connected by their root system. Radioisotopes injected in one tree will show up far away in another tree as the forest attempts to distribute the supply of sunshine. Trees that are in the sun share their good fortune with trees that are in the shade. But we do not see any of this because we are focused on the individual tree. The left brain sees only the discrete trees, not the entire forest.

  Being, metaphor, image, and music are the essence of art. Doing, reason, abstract thinking, and numbers are the crux of science. Art lives principally to the right, science to the left. Despite this division, only a handful of individuals in all of history were able to bridge this split. But, the stunning realization is that only one person in all of history was able to excel in both of these fields to achieve a unique synthesis.

  Chapter 14

  Space and Time/Space-Time

  The water you touch in a river is the last of that which has passed and the first of that which is coming. Thus it is with time present.

  —Leonardo da Vinci

  The reason why our sentient, percipient, and thinking ego is met nowhere in our world picture can easily be indicated in seven words: because it is ITSELF that world picture. It is identical with the whole and therefore cannot be contained in it as part of it.

  —Erwin Schrödinger

  Although all knowledge begins with experience, it does not necessarily all spring from experience.

  —Immanuel Kant

  In the eighteenth century, philosopher Immanuel Kant ­presented a series of prescient theories about the structure of consciousness. He could not have known at the time that modern neuroscientists would later confirm his hunches. Kant’s ideas provide a framework within which it is possible to understand how Leonardo’s brain’s unique structure fostered his creativity.

  In his cave analogy, Plato likened humans to a group of prisoners chained to a low wall. Above and behind them, the hurly-burly of community life went on. A large fire cast the shadows of these activities onto the wall. The prisoners’ shackles prevented them from turning around and seeing what was going on above the wall. Thus, the prisoners thought these flickering shadows were the real world.

  Building on Plato’s famous cave metaphor, Kant proposed that humans were similarly condemned to know the world only from a perch inside our skulls. We peer out through the chinks of our senses and perceive something we call “external reality.” We make a conscious distinction between “in here” and “out there.” Kant lamented the fact that we can never know for sure what is out there, an entity he called das Ding an sich—“the thing in itself.”

  Despite being confined behind our foreheads, we humans have certainly made a good go of trying to comprehend the outside world. Our facility with language allows us to do this. Resembling the four bases of DNA, we use a mental quaternary code to project our version of what is “out there” from inside our minds. The four elements are matter, energy, space, and time.

  Matter and energy are the two central characters in every sentence we utter. Matter roughly translates into “things.” Energy roughly translates into “actions.” Nouns (matter) and verbs (energy) are the backbone of our thoughts. Space and time are crucial qualifiers that add flesh to sentences, orienting the action taking place. Space is the stage upon which all verbal action takes place, and time sets the pace of the narrative. Because speech trips off our tongues one word after another, time is the critical dimension that channels all the words we speak into a single file.

  Kant’s role in the Leonardo story was his proposal concerning where these four constructs of reality arose.

  Recognizing that we humans had to start somewhere in our imagining of reality, Kant rooted his theory of human consciousness in what he called a priori assumptions, a phrase in Latin that means from the earlier. He proposed that we are born with an innate conception of two separate dimensions: space and time. Keeping time and space separate has been the key to Homo sapiens’ success. Whereas some animals may have developed a keen sense of their place in space and can navigate through this dimension (think of swallows, bats, and monkeys), very few animals can appreciate the complementary dimension of time.

  Through the work of Nobel laureate Eric Kandel, we now know that extremely primitive organisms such as sea slugs can hold the past within their rudimentary nervous systems. A proto memory is the key to anticipating what might happen. While there are many animals that can remember past events and have learned to distinguish friends from foes, there is only one that can easily roam along a line connecting past, present, and future, and it is us.

  We are born with two internal super-sense organs charged with collating information from our five external sense organs that enable us to understand our place in space and time. My argument is that Leonardo was an individual who had an altered perception of these two coordinates, and it was this that contributed to his extraordinary creativity.

  Kant’s hunch, hemispheric specialization, and Le
onardo’s creativity are all related. We are born with the capacity to easily maneuver in three vectors of space, a feat we share with many other creatures. But we can also imagine three durations of time. Our unique capacity to do this comes from something that occurred when Natural Selection split our brain in two.

  The split brain created an X axis of space and a Y axis of time. Humans plot the “real” world on this graph. Natural Selection designed human brains to appreciate space and time as two distinctly separate domains. Their separation gave us the enormous advantage in the competition for resources.

  In 1905, Albert Einstein added a new wrinkle to the space and time debate when he solved a problem that had pestered physicists since Newton. When Newton developed his grand theory concerning gravity, he was at a loss to explain the nature of the force that would attract two objects separated in space. To solve the problem, he imagined a clear, gelatinlike substance that permeated the universe. He called it the luminiferous aether. Because his reputation was so great, and the idea of two billiard balls in space being attracted to each other with nothing in between seemed absurd, Newton’s hypothesis was accepted with very few objections.

  Young Albert published a paper in the prestigious German journal, Annals of Physics, which has become commonly known as Einstein’s theory of special relativity. In arachnid equations crawling across the pages, he mathematically proved that light could travel through space and time, unsupported by any medium at all!

  Newton believed that space and time were invariable. Space was an inelastic container of the universe, and time was a river that flowed at a constant rate of speed. Einstein stood Newton’s formulation on its head. According to Einstein’s theory, both space and time were extremely malleable; only the speed of light was invariable. Einstein proposed that the speed of light remained constant, at 186,000 miles per second. Space and time deformed in such a way as to accommodate light so that its speed would always remain the same.