Brain Rule #5
Every brain is wired differently.
MICHAEL JORDAN’S ATHLETIC FAILURES are puzzling, don’t you think? In 1994, one of the best basketball players in the world—ESPN’s greatest athlete of the 20th century—decided to quit the game and take up baseball instead. It was an attempt to fulfill a childhood dream. Jordan failed miserably. He played only one full season, during which he posted a .202 batting average and committed 11 errors in the outfield: the league’s worst. Jordan’s performance was so poor, he couldn’t even qualify for a triple-A farm team. Though it seems preposterous that anyone with his physical ability could fail at any athletic activity he put his mind to, here was proof that one could. That same year, another athletic legend, Ken Griffey Jr., was burning up the baseball diamond. Like Jordan, Griffey Jr. played in the outfield but, unlike Jordan, he was known for catches so spectacular he seemed to float in the air. Float in the air? Wasn’t that the space Jordan was accustomed to inhabiting? But the sacred atmosphere of the baseball park refused to budge for Jordan, and he soon went back to what his brains and muscles did better than anyone else’s, creating a legendary sequel to an already stunning basketball career. Griffey, then playing for the red-hot Seattle Mariners, went on to bat .300 for seven years in the 1990s and, in that same decade, slug out 382 home runs. He is still sixth on the all-time home-runs list.
What made the talents of these two athletes so specialized? What was going on with the way their brains communicated better with certain muscles than others? It has to do with how their brains were wired. To understand what that means, we will take a guided tour through the brain to watch what happens as it is learning. We will discuss the enormous role of one’s experience in how one’s brain develops—including the fact that identical twins having an identical experience will not emerge with identical brains. And we will discover that we each have a Jennifer Aniston neuron. I am not kidding.
Learning rewires your brain
When you learn something, the wiring in your brain changes. Eric Kandel is the scientist mostly responsible for showing that acquiring even simple pieces of information physically alters the structure of our neurons. Taken broadly, these physical changes result in the functional organization and reorganization of the brain. This is astonishing. The brain is constantly learning things, so the brain is constantly rewiring itself.
Kandel first discovered this fact not by looking at humans but by looking at sea slugs. He soon found, somewhat insultingly, that human nerves learn things in the same way slug nerves learn things. And so do lots of animals in between slugs and humans. Kandel shared a Nobel Prize in 2000 for his work in part because it described the thought processes of virtually every creature with the means to think.
What are these physical alterations? As neurons learn, they swell, sway, and split. They break connections in one spot, glide over to a nearby region, and form connections with their new neighbors. Many others stay put, simply strengthening their electrical connections with each other, increasing the efficiency of information transfer. Indeed, at this very moment inside your brain, bits of neurons are moving around like reptiles: slithering to new spots, getting fat at one end or creating split ends. All so that you can remember a few things about Eric Kandel and sea slugs.
This line of scientific inquiry started long before Kandel. In the 18th century, the Italian scientist Vincenzo Malacarne did a surprisingly modern series of biological experiments. He trained a group of birds to do complex tricks, then killed them and dissected their brains. He found that his trained birds had more extensive folding patterns in specific regions of their brains than his untrained birds. Fifty years later, Charles Darwin noted similar differences between the brains of wild animals and their domestic counterparts. The brains of wild animals were 15 to 30 percent larger than those of their tame, domestic counterparts. It appeared that the cold, hard world forced the wild animals into a constant learning mode. Those experiences wired their brains much differently.
It is the same with humans. This can be observed in places ranging from New Orleans’s Zydeco beer halls to the staid palaces of the New York Philharmonic—both the natural habitat of violin players. In violin players’ brains, the neural regions that control their left hands, where complex, fine motor movement is required on the strings, look as if they’ve been gorging on a high-fat diet. These regions are enlarged, swollen, and crisscrossed with complex associations. By contrast, the areas controlling the right hand, which draws the bow, look positively anorexic, with much less complexity.
The brain acts like a muscle: The more activity you do, the larger and more complex it can become. Whether that equates to more intelligence is another issue, but one fact is indisputable: What you do in life physically changes what your brain looks like. You can wire and rewire your brain with the simple choice of which musical instrument—or professional sport—you play.
Where wiring starts: the humble cell
You have heard since grade school that living things are made of cells, and for the most part, that’s true. There isn’t much that complex biological creatures can do that doesn’t involve cells. You may have little gratitude for cells’ generous contribution to your existence, but the cells make up for your indifference by ensuring that you can’t control them. For the most part, they purr and hum behind the scenes, content to supervise virtually everything you will ever experience, much of which lies outside your awareness. Some cells are so unassuming, they find their normal function only after they can’t function. The surface of your skin, for example—all nine pounds of it—literally is deceased. This allows the rest of your cells to support your daily life free of wind, rain, and spilled nacho cheese at a baseball game. It is accurate to say that nearly every inch of your outer physical presentation to the world is dead.
Of the cells that are alive, most look just like fried eggs. The white of the egg we call the cytoplasm; the center yolk is the nucleus. The nucleus contains that master blueprint molecule, DNA. DNA possesses genes, small snippets of biological instructions, that guide everything from how tall you become to how you respond to stress. A lot of genetic material fits inside that yolk-like nucleus. Nearly six feet of the stuff are crammed into a space that is measured in microns. A micron is 1/25,000th of an inch, which means putting DNA into your nucleus is like taking 30 miles of ribbon and stuffing it into an eggshell.
One of the most unexpected findings of recent years is that DNA, or deoxyribonucleic acid, is not randomly jammed into the nucleus. Rather, DNA is folded into the nucleus in a complex and tightly regulated manner. The reason for this molecular origami: cellular career options. Fold the DNA one way and the cell will become a contributing member of your liver. Fold it another way and the cell will become part of your busy bloodstream. Fold it a third way and you get the all-important nerve cell—and the ability to read this sentence.
What does a nerve cell look like? Like an uprooted tree: a large mass of roots on one end, connected to a small mass of branches on the other. The root mass in a nerve cell is called the cell body, and within it lies the nucleus. The tips of the roots are called dendrites. The thin, connecting trunk is called an axon, and the smaller mass of branches is called the axon terminal.
Nerve cells—also called neurons—help to mediate something as sophisticated as human learning. To understand how, I would like to take you on a guided tour of a neuron, borrowing from a science-fiction movie I saw as a child. It was called Fantastic Voyage, written by Harry Kleiner and popularized afterward in a book by the legendary Isaac Asimov. In the movie, four people are shrunk to microscopic size, and they board a tiny submarine to explore the internal workings of the human body. We are going to do the same. We’ll roam around inside a typical neuron and the watery world in which it is anchored. Let’s steer over to the hippocampus, the structure in the center of the brain where short-term knowledge is converted to longer-term knowledge.
When our little ship enters the hippocampus, our eyes adjust to the darkness and we peer out the windows. It looks as if we’ve entered an ancient, underwater forest. Everywhere there are submerged jumbles of branches, limbs, and trunks. Suddenly we see flashes of light in the darkness: sparks of electric current run up and down the trunks. The forest is electrified! We are going to have to be careful. Occasionally, large clouds of chemicals erupt from one end of the tree trunks, after electricity has convulsed through them.
These are not trees. These are neurons, with some odd structural distinctions. Sliding alongside one of the trunks, for example, we realize that the “bark” seems surprisingly slick, like grease. That’s because it is grease. In the balmy interior of the human body, the exterior of the neuron, the phospholipid bilayer, is the consistency of Mazola oil. The neuron’s interior structure is what gives it its shape, much as the human skeleton gives the body its shape. When we plunge into the interior of the cell, one of the first things we will see is this skeleton. So let’s plunge.
It’s instantly, insufferably overcrowded, even hostile, in here. Everywhere we have to navigate through a dangerous scaffolding of spiky, coral-like protein formations: the neural skeleton. Though these dense formations give the neuron its three-dimensional shape, many of the skeletal parts are in constant motion—which means we have to do a lot of dodging. Millions of molecules still slam against our ship, however, and every few seconds we are jolted by electrical discharges. We don’t want to stay long.
We escape from one end of the neuron. Instead of perilously winding through sharp thickets of proteins, we now find ourselves free-floating in a calm, seemingly bottomless watery canyon. In the distance, we can see another neuron looming ahead. We are in the space between two neurons, called a synaptic cleft, and the first thing we notice is that we are not alone. We appear to be swimming with large schools of tiny molecules. They are streaming out of the neuron we just visited and thrashing helter-skelter toward the one we are facing. In a few seconds, they reverse themselves, swimming back to the neuron we just left. It instantly gobbles them up. These schools of molecules are called neurotransmitters, and they function like tiny couriers. Neurons use these molecules to communicate information across the synaptic cleft. The cell that releases them is called the presynaptic neuron, and the cell that receives them is called the postsynaptic neuron.
Neurons release these chemicals into the synapse usually in response to being electrically stimulated. The neuron that receives these chemicals then reacts negatively or positively. In something like a cellular temper tantrum, the neuron can turn itself off to the rest of the neuroelectric world—a process termed inhibition. Or the neuron can become electrically stimulated, allowing a signal to be transferred: “I got stimulated and I am passing on the good news to you.” The neurotransmitters then return to the cell of origin, a process appropriately termed reuptake. When that cell gobbles them up, the system is reset and ready for another signal.
As we gaze at this underwater hippocampal forest, we notice several disturbing developments. Some of these branches appear to be swaying, snakelike. Occasionally, the end of one neuron swells up, greatly increasing in diameter. The terminal ends of other neurons split down the middle like forked tongues, creating two connection points where there was only one. Electricity crackles through these moving neurons at a blinding 250 miles per hour, some quite near us, with clouds of neurotransmitters filling the synaptic spaces as the electric current passes by.
What we should do now is take off our shoes and bow low in our submarine, for we are on Neural Holy Ground. We are observing the process of the human brain learning.
As we slowly spin our ship 360 degrees, we notice how complicated this forest is. Take the two neurons between which we are floating. We are between just two connection points, two dendrites. If you can imagine two trees being uprooted by giant hands, turned 90 degrees so that the roots face each other, and then moved close enough to almost touch, you can visualize the real world of two neurons interacting in the brain. And that’s just the simplest case. Usually, thousands of neurons are jammed up against one another, all occupying a single small parcel of real estate in the brain. The branches form connections with one another in a nearly incomprehensible mass of confusion. Ten thousand points of connection is typical.
Frenetic growth and frantic pruning
How do we get so many neurons? Infants provide a front-row seat to one of the most remarkable construction projects on Earth. The human brain, only partially constructed at birth, won’t be fully assembled for years. The biggest construction programs aren’t finished until you are in your early 20s, with fine-tuning well into your 40s. When babies are born, their brains have about the same number of connections as adults have. That doesn’t last long. By the time children are 3 years old, the connections in specific regions of their brains have doubled or even tripled. That doesn’t last long, either. The brain soon takes thousands of tiny pruning shears and trims back a lot of this hard work. By the time children are 8 or so, they’re back to their adult numbers. And if kids never went through puberty, that would be the end of the story. In fact, it is only the middle of the story. At puberty, the whole process begins again, but with different regions in the brain. Once again, you see frenetic neural outgrowth and furious pruning back. It isn’t until parents begin thinking about college financial aid that children’s brains begin to settle into their adult forms. From a connectivity point of view, there is a great deal of activity in the terrible twos and then, during the terrible teens, a great deal more.
Because this happens to every person at about the same time, it might seem like cellular soldiers are obeying growth commands in lockstep formation. But nothing approaching military precision is observed in the messy world of brain development. And it is at this imprecise point that brain development meets Brain Rule: Every brain is wired differently. Even a cursory inspection of the data reveals remarkable variation in growth patterns from one person to the next. Whether examining toddlers or teenagers, different regions in different children develop at different rates. There is a remarkable degree of diversity in the specific areas that grow and prune, and with what enthusiasm they do so.
I’m reminded of this whenever I see the class pictures from my wife’s journey through the American school system. My wife went to school with virtually the same people for her entire K–12 experience (and actually remained friends with most of them). Comparing the kids to each other back then, I always shake my head in disbelief. In the first-grade picture, the kids are all about the same age, but they don’t look it. Some kids are short. Some are tall. Some look like mature little athletes. Some look as if they just got out of diapers. The girls almost always appear older than the boys. It’s even worse in the junior-high pictures. Some of the boys look as if they haven’t developed much since third grade. Others are clearly beginning to sprout whiskers. Some of the girls, flat-chested, look a lot like boys. Others look developed enough to make babies. And if we could look inside these kids’ heads, we would see that their brains are just as unevenly developed as their bodies. Let’s find out why.
The Jennifer Aniston neuron
Some of the neural connections you’re born with have preset functions: they control basic housekeeping functions like breathing, heartbeat, your ability to know where your foot is even if you can’t see it, and so on. Researchers call this “experience independent” wiring. The brain also holds off connecting neurons, waiting for external experience to direct it. “Experience expectant” wiring is related to areas such as visual acuity and perhaps language acquisition. And, finally, we have “experience dependent” wiring. It may best be explained by the following scene, which would be right at home in a grade B movie.
A man is lying on a surgical table, electrodes implanted in his brain to create a kind of GPS pinpointing electrical activity in the brain. The man needs to have some of his neural tissue removed—resected, in surgical parlance—because of life-threatening epilepsy, and the depth electrodes will help surgeons determine where the seizures are starting. The man is conscious. Suddenly, a researcher whips out a photo of Jennifer Aniston and shows it to the patient. A neuron in the man’s head fires. The researcher lets out a war whoop.
This experiment really happened. The neuron in question responded to seven photographs of actress Jennifer Aniston, while it practically ignored the 80 other images of everything else, including famous and nonfamous people. Lead scientist Quian Quiroga said, “The first time we saw a neuron firing to seven different pictures of Jennifer Aniston—and nothing else—we literally jumped out of our chairs.” There is a neuron lurking in your head that is stimulated only when Jennifer Aniston is in the room.
A Jennifer Aniston neuron? How could this be? Surely nothing in our evolutionary history suggests that Jennifer Aniston is a permanent denizen of our brain wiring. (Aniston wasn’t even born until 1969, and there are regions in our brain whose designs are millions of years old). To make matters worse, the researchers also found a Halle Berry–specific neuron, a cell in a patient’s brain that wouldn’t respond to pictures of Aniston or anything else. Just Berry. A patient also had a neuron specific to Bill Clinton. It no doubt was helpful to have a sense of humor while doing this kind of brain research.
Welcome to the world of experience-dependent brain wiring, where a great deal of the brain is hardwired not to be hardwired. Like a beautiful, rigorously trained ballerina, we are hardwired to be flexible. We can immediately divide the world’s brains into those who know of Jennifer Aniston or Halle Berry or Bill Clinton and those who don’t. The brains of those who do are wired differently from those who don’t. This seemingly ridiculous observation underlies a much larger concept. Our brains are so sensitive to external inputs that their physical wiring depends upon the culture in which they find themselves.
Even identical twins do not have identical brain wiring. Consider this thought experiment: Suppose two adult male twins rent the Halle Berry movie Catwoman, and we in our nifty little submarine are viewing their brains while they watch. Even though the twins are in the same room, sitting on the same couch, the twins see the movie from slightly different angles. We find that their brains are encoding visual memories of the video differently, in part because it is impossible to observe the video from the same spot. Seconds into the movie, they are already wiring themselves differently. One of the twins earlier in the day read a magazine story about panned action movies, a picture of Berry figuring prominently on the cover. While watching the video, this twin’s brain is simultaneously accessing memories of the magazine story. We observe that his brain is busy comparing and contrasting comments from the text with the movie and is assessing whether he agrees with them. The other twin has not seen this magazine, so his brain isn’t doing this. Even though the difference may seem subtle, the two brains are creating different memories of the same movie.
That’s the power of the Brain Rule. Learning results in physical changes in the brain, and these changes are unique to each individual. Not even identical twins having identical experiences possess brains that wire themselves exactly the same way. Given this, can we know anything about the organ? Well, yes. The brain has billions of cells whose collective electrical efforts work in a similar fashion. Every human comes equipped with a hippocampus, a pituitary gland, and the most sophisticated thinking store of electrochemistry on the planet: a cortex. These tissues function the same way in every brain. How then can we explain the individuality? Consider a highway.
For each brain, a different road map
The United States has one of the most extensive and complex ground transportation systems in the world. There are lots of variations on the idea of “road,” from interstate freeways, turnpikes, and state highways to residential streets, one-lane alleys, and dirt roads. Pathways in the human brain are similarly diverse. We have the neural equivalents of large interstate freeways, turnpikes, and state highways. These big trunks are the same from one person to the next, functioning in yours about the same way they function in mine. So a great deal of the structure and function of the brain is predictable. This may be the ultimate result of the double-humped growth and pruning program we talked of previously. That’s the experience-independent wiring.
It’s when you get to the smaller routes—the brain’s equivalent of residential streets, one-laners and dirt roads—that individual patterns begin to show up. In no two people are they identical. That’s the experience-dependent wiring. Every brain has a lot of these smaller paths, which is why the very small amounts to a big deal. It’s why, for example, human intellect is so multifaceted. Psychologist Howard Gardner believes we have at least seven categories of intelligence: verbal/linguistic, musical/rhythmic, logical/mathematical, spatial, bodily/kinesthetic, interpersonal, and intrapersonal. It’s a much broader idea of intelligence than the standard IQ test implies.
We can grasp the magnitude of each brain’s differences by watching a skilled neurosurgeon at work. George Ojemann has a shock of white hair, piercing eyes, and the quiet authority of someone who for decades has watched people live and die in the operating room. He is one of the great neurosurgeons of our time, and he is an expert at a technique called electrical stimulation mapping.
Ojemann is hovering over the exposed brain of a man with severe epilepsy. The man’s name is Neil. Ojemann is there to remove some of Neil’s misbehaving brain cells. Before Ojemann takes anything out, however, he has to make a map. To do this, he needs to talk to Neil during surgery, so Neil is fully conscious. Fortunately, the brain has no pain receptors. Ojemann wields a thin silver wire, which sends out small, unobtrusive electrical shocks to anything it touches. If it brushed against your hand, you would feel only a slight tingling sensation. Ojemann gently touches one end of the wire to an area of his patient’s brain. In the book Conversations with Neil’s Brain, he describes what happens next:
“Feel anything?”
“Hey! Someone touched my hand,” Neil volunteers. Neither the anesthesiologist nor I had come anywhere close to Neil’s hand.
“Which hand?” asks George.
“My right one, sort of like someone brushed the back side of it. It’s still tingling a little.” The right hand reports to the left side of the brain, and George evidently has located the hand area of [the] somatosensory cortex with the stimulator.
Ojemann marks the area by putting a small sterile piece of paper on it. He touches another spot. Neil says he feels something near his right cheek. Another tiny piece of paper. This call and response goes on for hours. Like a neural cartographer, Ojemann is mapping the various functions of his patient’s brain, with special attention paid to the areas close to the epileptic tissue.
These are tests of the patient’s motor skills. For reasons not well understood, however, epileptic tissues are often disturbingly adjacent to areas critical for language. So Ojemann also pays close attention to the regions involved in language processing, where words and sentences and grammatical concepts are stored. If the patient is bilingual, he will map critical language areas for both Spanish and English. He applies a paper dot marked S to the regions where Spanish exists, and he applies a small E where English is stored. Ojemann does this painstaking work with every single patient who undergoes this type of surgery. Why? The answer is a stunner. He has to map each individual’s critical function areas because he doesn’t know where they are.
Ojemann can’t predict the function of very precise areas in advance of the surgery because no two brains are wired identically. Not in terms of structure. Not in terms of function. For example, from nouns to verbs to aspects of grammar, we each store language in different areas, recruiting different regions for different components. Bilingual people don’t even store their Spanish and their English in similar places.
This individuality has fascinated Ojemann for years. He once combined the brain maps for 117 patients he had operated on over the years. Only in one region did he find a spot where most people had a critical language area, and “most” means 79 percent of the patients.
Data from electrical stimulation mapping give the most dramatic illustration of the brain’s individuality. But Ojemann also wanted to know how stable these differences were during life, and if any of those differences predicted intellectual competence. He found interesting answers to both questions. First, the brain’s road maps are established very early in life, and they remain stable throughout. Even if a decade or two had passed between surgeries, the brain region recruited to host a critical language area remained the same. Second, Ojemann found that structural differences were associated with performance on a language test (given before surgery). If patients performed poorly on the test, the wiring pattern of their critical language area tended to be widely distributed. It was tightly focused in patients who performed well on the test. Lower scores on the test also predicted that a patient’s critical language area had taken up residence in the superior temporal gyrus, as opposed to another brain region. Again, experience had wired each brain differently, with real-world consequences.
More ideas
Does it make any sense that most schools expect every child to learn like every other? For example, we expect that kids should be able to read by age 6. Yet students of the same age show a great deal of intellectual variability. Studies show that about 10 percent of students do not have brains sufficiently wired to read at that age. And does it make any sense that most businesses strive to treat each employee the same, especially in a global economy replete with various cultural experiences? As you can guess, I don’t think so. Here are a few ideas for aligning our schools and businesses with the way the brain works.
All else being equal, it has been known for many years that smaller, more intimate schools create better learning environments than megaplex houses of learning. Smaller is better because a teacher can deeply understand the individual needs of only so many students. If you are a parent, you can look for (and lobby for) schools with smaller classes or a more favorable teacher-student ratio. A college student might consider attending a smaller school. A manager looking to train employees should do it in smaller groups.
Theory of Mind testing
As you may recall from the Introduction, Theory of Mind is about as close to mind reading as humans get. It is the ability to understand the interior motivations of someone else and the ability to construct a predictable “theory of how their mind works.” Nearly all of us can do it, but some of us are better at it than others.
Theory of Mind skills give teachers critical knowledge about their students, a heightened sensitivity for when they are confused, when they are fully engaged, and when they have truly learned what is being taught. I have come to believe that people with advanced Theory of Mind skills possess the single most important ingredient for effectively communicating information. If I’m right, it’s possible that the best teachers possess advanced Theory of Mind skills and the worst teachers don’t.
In the future, Theory of Mind tests should be as standard as IQ tests. Schools and other organizations could use the tests to reveal the better teachers. Companies could include Theory of Mind tests as they screen for leaders. People considering careers as teachers or managers could take the tests to help them decide whether they’re a good fit for the role.
Customized classrooms and workplaces
As an instructor teaches a class, students inevitably will experience learning gaps. Left untreated, these gaps cause students to fall further behind. Developers of educational apps are using software to determine where a student’s competencies lie and then adaptively tailor exercises for the student in order to fill in any gaps. The effect is greatest when the software is integrated into a school program. In a large classroom, teacher alone or software alone is not as effective. I would like to see more research on this—as would parents and teachers anxious about the infiltration of tablets into classrooms. Studies should include typical and optimized student-teacher ratios.
Parents could embrace the apps and pay close attention to the effect on their kids. Parents could look for a school adopting the trend of a flipped classroom, where students review the lecture at home before class. Class time is instead spent on homework, and teachers give individualized help as needed. Parents who are financially able might choose schools organized around the idea that children learn different things at different speeds, such as Montessori schools. Students can supplement school classes with free online courses, which allow them to view and review material at their own pace, such as those available through Khan Academy.
As for employees working at organizations who treat all people the same way, it will be up to you to push for the things you value: the balance of vacation time versus pay, a flexible schedule, the way your role within the company works. If you’re a manager, make a list of the cognitive strengths of your team. Some of your employees may be great at memorizing things. Others may be better at quantitative tasks. Some have good people skills. Some don’t. Assigning work projects based on an employee’s strengths may be critical to your group’s productivity. You may discover you had a Michael Jordan on your team but couldn’t see it because you were only asking him to play baseball.
Brain Rule #5
Every brain is wired differently.
• What you do and learn in life physically changes what your brain looks like—it literally rewires it.
• The various regions of the brain develop at different rates in different people.
• Neurons go through a growth spurt and pruning project during the terrible twos and teen years.
• No two people’s brains store the same information in the same way in the same place.
• We have a great number of ways of being intelligent, many of which don’t show up on IQ tests.
