Think about the way a schoolchild will look at a globe of the earth and assume there is something fundamental and unchanging about the country borders. In contrast, a professional historian understands that country borders are functions of happenstance and that our story could have been run with slight variations: a would-be king dies in infancy, or a corn pestilence is avoided, or a warship sinks and a battle tips the other way. Small changes would cascade to yield different maps of the world.

      And so it goes with the brain. Although a traditional textbook drawing suggests that neurons in the brain are happily packed next to one another like jelly beans in a jar, don’t let the cartoon fool you: neurons are locked in competition for survival. Just like neighboring nations, neurons stake out their territories and chronically defend them. They fight for territory and survival at every level of the system: each neuron and each connection between neurons fights for resources. As the border wars rage through the lifetime of a brain, maps are redrawn in such a way that the experiences and goals of a person are always reflected in the brain’s structure. If an accountant drops her career to become a pianist, the neural territory devoted to her fingers will expand; if she becomes a microscopist, her visual cortex will develop higher resolution for the small details she seeks; if she becomes a perfumer, her brain regions assigned to smell will enlarge.

      It is only from a dispassionate distance that the brain gives the illusion of a globe with predestined and definitive borders.

      The brain distributes its resources according to what’s important, and it does so by implementing do-or-die competition among all the parts that make it up. This basic principle will illuminate several questions we’ll encounter shortly: Why do you sometimes feel as though your cell phone just buzzed in your pocket, only to discover it’s on the table? Why does the Austrian-born actor Arnold Schwarzenegger have a thick accent when he speaks American English, while the Ukrainian-born actress Mila Kunis has none? Why is a child with autistic savant syndrome able to solve a Rubik’s Cube in forty-nine seconds but unable to hold a normal conversation with a peer? Can humans leverage technology to build new senses, thus gaining a direct perception of infrared light, global weather patterns, or the stock market?

IF YOU’RE MISSING THE TOOL, CREATE IT

      At the end of 1945, Tokyo found itself in a bind. Through the period that spanned the Russo-Japanese War and two world wars, Tokyo had devoted forty years of intellectual resources to military thinking. This had equipped the nation with talents best suited for only one thing: more warfare. But atomic bombs and the fatigue of combat had abated its appetite for conquest in Asia and the Pacific. War was over. The world had changed, and the Japanese nation was going to have to change with it.

      But change invited a difficult question: What would they do with their vast numbers of military engineers who, since the dawn of the century, had been trained to produce better weaponry? These engineers simply didn’t mesh with Japan’s newly discovered desire for tranquility.

      Or so it seemed. But over the next few years, Tokyo shifted its social and economic landscape by redeploying its engineers toward new assignments. Thousands were tasked with building the high-speed bullet train known as the Shinkansen.⁵ Those who had previously designed aerodynamic navy aircraft now crafted streamlined railcars. Those who had worked on the Mitsubishi Zero fighter plane now devised wheels, axles, and railing to ensure the bullet train could operate safely at high speeds.

      Tokyo shaped its resources to better match its external environment. It beat its swords into plowshares. It altered its machinery to match the demands of the present.

      Tokyo did what brains do.

      The brain chronically adjusts itself to reflect its challenges and goals. It molds its resources to match the requirements of its circumstance. When it doesn’t possess what it needs, it sculpts it.

      Why is that a good strategy for the brain? After all, human-built technology has been very successful, and we use an entirely different strategy there. We build fixed hardware devices with software programs to neatly accomplish what we need. What would be the advantage of melting the distinction between those layers so that the machinery is constantly redesigned by the running of the programs?

      The first advantage is speed.⁶ You type rapidly on your laptop because you don’t have to think about the details of your fingers’ positions, aims, and goals. It all just proceeds on its own, seemingly magically, because typing has become part of your circuitry. By reconfiguring the neural wiring, tasks like this become automatized, allowing fast decisions and actions. Millions of years of evolution didn’t presage the arrival of written language, much less a keyboard, and yet our brains have no trouble taking advantage of the innovations.

      Compare this with hitting the correct keys on a musical instrument you’ve never played before. For these sorts of untrained tasks, you rely on conscious thinking, and that is comparably quite slow. This speed difference between amateurism and expertise is why a leisure soccer player constantly has the ball stolen. In contrast, the experienced player reads the signals of his opponents, capers with fancy footwork, and shoots the ball with high precision. Unconscious actions are more rapid than conscious deliberation. Plows farm faster than swords.

      The second advantage of specializing the machinery for important tasks is energy efficiency. The newbie soccer player simply doesn’t understand how all the movement of the field fits together, while the pro can manipulate the game play in multiple ways to score a goal. Whose brain is more active? You might guess it’s the high-scoring expert—because he understands the structure of the game and is zipping through possibilities, decisions, and intricate moves. But that would be the wrong guess. The expert’s brain has developed neural circuitry specific to soccer, allowing him to make his moves with surprisingly little brain activity. In a sense, the expert has made himself one with the game. In contrast, the amateur’s brain is on fire with activity. He’s trying to figure out which movements matter. He’s entertaining multiple interpretations of the situation and trying to determine which, if any, are correct.

      As a result of burning soccer into the circuitry, the pro’s performance is both fast and efficient. He’s optimized his internal wiring for that which is important in his outside world.

AN EVER-CHANGING SYSTEM

      The concept of a system that can be changed by external events—and keep its new shape—led the American psychologist William James to coin the