Our three examples of tuning and pruning demonstrate how the social world profoundly shapes the physical reality of the brain’s wiring. Who knew that caregivers were such effective electricians?
This arrangement comes with a risk, however. Little brains require a social world in order to develop typically. You’ve already learned that babies need certain physical inputs, such as photons of light bombarding their retinas, or their brains will never develop normal vision. It turns out that they also need social inputs from other humans who guide their attention, speak or sing to them, and cuddle them at key moments. If these needs aren’t met, things can go terribly wrong.
I wish we didn’t know what happens when a baby’s brain receives too little social input. Nobody should ever deprive babies of what they need to thrive. But unfortunately, we do know some distressing details because of a tragic historical event.
In the 1960s, the Communist government of Romania outlawed most contraception and abortion. The president, Nicolae Ceauşescu, wanted to expand the population to become more of an economic power and, therefore, a world power. This new law produced a huge increase in births, more children than many families could afford. As a consequence, hundreds of thousands of children were sent to live in orphanages. Many were appallingly mistreated. The children who are most relevant to our lesson here are the ones whose social needs went unmet.
In some orphanages, babies were warehoused in rows of cribs, with little stimulation or social interaction. Nurses or caregivers would come in and feed them, change them, and put them back in the cribs. That was about it. Nobody cuddled these babies. No one played with them. No one conversed with or sang to them, or shared attention. They were ignored.
As a consequence of this social neglect, the Romanian orphans grew up intellectually impaired. They had problems learning language. They had difficulty concentrating and resisting distractions, probably because nobody had shared attention with them, so their brains never developed the wiring for an effective spotlight. They also had trouble controlling themselves. Alongside the children’s mental and behavioral issues, their bodies were stunted, most likely because they grew up without caregivers to keep their body budgets solvent. This meant their brains never learned to budget effectively. A little brain wires itself to its environment, and when that environment is missing key elements for healthy body budgeting, critical brain wiring can be pruned away.
These aftereffects are consistent with what scientists know about other babies raised in severely socially impoverished conditions. Their brains develop smaller than average. Key brain regions are smaller too, and important areas of the cerebral cortex have fewer connections. If such children are moved to traditional foster homes in the first few years of life, some of these effects are reversible. Similar risks can arise for any kids reared in institutions without attentive, consistent caregivers, whether these institutions are orphanages, refugee camps, or immigrant detention centers.
When children are persistently neglected, in all likelihood they’ll suffer ill effects eventually. The impact might not be immediate and dramatic, as in the Romanian orphanages, but can be gradual and subtle as important wiring goes unused and is steadily pruned away. The fallout may build up over time like a slow drip from a water pipe that eventually bores a hole through your floorboards. For example, a neglected little brain in a socially impoverished environment may wire itself to manage its own body budget alone, without the social support from caregivers and the wiring instructions they provide through their actions. This nontypical wiring imposes a pernicious burden on the body budget that accumulates over years, raising the odds of serious health problems later, such as heart disease, diabetes, and mood disorders like depression, all of which have metabolic underpinnings.
To be clear, I’m not saying that we have to keep our little darlings free of stress or their brains and bodies will break. I’m saying that persistent neglect, over a long time with no relief, is almost always harmful to a little brain. The scientific evidence is clear on this point. You can’t just feed and water babies and expect their brains to grow normally. You must also meet their social needs with eye contact and language and touch. If these needs go unmet, the seeds of illness may be planted very, very early.
We see similar consequences when little brains develop in poverty. Research shows that early and long exposure to poverty is bad for the developing brain. Inadequate nutrition, interrupted sleep due to street noise, poor temperature regulation due to lack of heat or ventilation, and other circumstances of poverty may alter the development of the front of the cerebral cortex, namely the prefrontal cortex. This brain area is involved in a range of critical functions, including attention, language, and body budgeting. Scientists are still studying the ways that poverty affects brain development, but we do know that it’s linked to poorer performance in school and fewer years of education. These burdens ultimately increase a child’s risk of living in poverty when he grows up and has children of his own. It wouldn’t surprise me if this vicious cycle reinforces negative stereotypes about people who live in poverty. Society is quick to blame genes when poverty endures across generations for a group of people. But it’s plausible that those little brains are being molded by poverty.
Some kids are fortunate enough to be naturally resilient to the insidious effects of adversity and poverty. But on average, adversity and poverty are afflictions from which little brains struggle to recover. What’s truly frustrating is that this tragedy is preventable. (Pardon me while I take off my scientist’s hat for a moment.) Politicians have dragged their feet for decades about lifting children out of poverty. So let’s set the politics aside and frame the issue in simple financial terms: Childhood poverty is a colossal waste of human opportunity. Recent estimates suggest that it’s far cheaper to eradicate poverty than to deal with its effects decades later. More school districts can offer free meal programs to students in need. Cities can set up noise ordinances for poor neighborhoods. These sorts of steps are not merely about quality of life. They create the conditions for healthy brain development, so all children can become the workers, citizens, and innovators of the next generation.
Given the powerful impact of neglect and poverty on a little brain, it’s tempting to ask how evolution got our species into this precarious situation in the first place. It’s risky for a baby’s brain wiring to depend so critically on social and physical input in order to develop typically. We humans must gain some advantage to offset the risks of developing this way. So what is it?
We can’t know for sure, but here is my guess based on evidence from evolutionary biology and anthropology: This arrangement helps our cultural and social knowledge flow efficiently from generation to generation. Each little brain becomes optimized for its particular environment, the one it developed in. Caregivers curate a baby’s physical and social niche, and the baby’s brain learns that niche. When the baby grows up, he perpetuates that niche by passing his culture to the next generation through his words and actions, wiring their brains in turn. This process, called cultural inheritance, is efficient and frugal because evolution doesn’t have to encode all our wiring instructions in genes. It off-loads much of the job to the world around us, including the other humans in that world. We unknowingly wire the knowledge of our culture into our offspring after birth, for better or worse.
When it comes to the brain, simple distinctions like nature versus nurture are alluring but not realistic. We have the kind of nature that requires nurture. Your genes require a physical and social environment—a niche filled with other humans who shared your infant gaze, spoke to you with intent, set your sleep schedule, and controlled your body temperature—in order to produce a finished brain.
We all know that it matters how we treat our children, but it matters more than we knew even a few decades ago. When you’re awake at four a.m. trying to console your shrieking little angel, or when he calmly drops his Cheerios onto the floor for the ninety-third time, you are
guiding his tuning and pruning whether you know it or not. Little brains wire themselves to their world. It’s up to us to create that world—including a social world rich with wiring instructions—to grow those brains healthy and whole.
Lesson No.
4
Your Brain Predicts (Almost) Everything You Do
A FEW YEARS AGO, I received an e-mail from a man who served in the Rhodesian army in southern Africa in the 1970s, before the end of apartheid. He’d been drafted against his will, handed a uniform and a rifle, and ordered to hunt down guerrilla fighters. To make matters worse, before the draft, he’d been an advocate for the same guerrillas that he was now required to treat as the enemy.
He was deep in the forest one morning, conducting practice exercises with his small squad of soldiers, when he detected movement ahead of him. With a pounding heart, he saw a long line of guerrilla fighters dressed in camouflage and carrying machine guns. Instinctively, he raised his rifle, flipped off the safety catch, squinted down the barrel, and aimed at the leader, who was carrying an AK-47 assault rifle.
Suddenly, he felt a hand on his shoulder. “Don’t shoot,” whispered his buddy behind him. “It’s just a boy.” He slowly lowered his rifle, looked again at the scene, and was astonished by what he now saw: a boy, perhaps ten years old, leading a long line of cows. And the dreaded AK-47? It was a simple herding stick.
For years afterward, this man struggled to understand the unsettling episode. How had he managed to mis-see what was right in front of his eyes and nearly kill a child? What was wrong with his brain?
As it turns out, nothing was wrong with his brain. It was working exactly as it should have.
Scientists used to believe that the brain’s visual system operated sort of like a camera, detecting the visual information “out there” in the world and constructing a photograph-like image in the mind. Today we know better. Your view of the world is no photograph. It’s a construction of your brain that is so fluid and so convincing that it appears to be accurate. But sometimes it’s not.
To understand why it can be perfectly normal to see a grown guerrilla fighter with a rifle when you’re looking at a ten-year-old boy with a stick, let’s consider the situation from the brain’s point of view.
From the moment you’re born to the moment you draw your last breath, your brain is stuck in a dark, silent box called your skull. Day in and day out, it continually receives sense data from the outside world via your eyes, ears, nose, and other sensory organs. This data does not arrive in the form of the meaningful sights, smells, sounds, and other sensations that most of us experience. It’s just a barrage of light waves, chemicals, and changes in air pressure with no inherent significance.
Faced with these ambiguous scraps of sense data, your brain must somehow figure out what to do next. Remember, your brain’s most important job is to control your body so you stay alive and well. Your brain must somehow make meaning from the onslaught of sense data it’s receiving so you don’t fall down a staircase or become lunch for some wild beast.
How does your brain decipher the sense data so it knows how to proceed? If it used only the ambiguous information that is immediately present, then you’d be swimming in a sea of uncertainty, flailing around until you figured out the best response. Luckily, your brain has an additional source of information at its disposal: memory. Your brain can draw on your lifetime of past experiences—things that have happened to you personally and things that you’ve learned about from friends, teachers, books, videos, and other sources. In the blink of an eye, your brain reconstructs bits and pieces of past experience as your neurons pass electrochemical information back and forth in an ever-shifting, complex network. Your brain assembles these bits into memories to infer the meaning of the sense data and guess what to do about it.
Your past experiences include not only what happened in the world around you but also what happened inside your body. Was your heart beating quickly? Were you breathing heavily? Your brain asks itself in every moment, figuratively speaking, The last time I encountered a similar situation, when my body was in a similar state, what did I do next? The answer need not be a perfect match for your situation, just something close enough to give your brain an appropriate plan of action that helps you survive and even thrive.
This explains how the brain plans your body’s next action. How does your brain also conjure high-fidelity experiences, like guerrilla fighters in the forest, out of scraps of raw data from the outside world? How does it create feelings of terror from a thundering heart? Once again, your brain recreates the past from memory by asking itself, The last time I encountered a similar situation, when my body was in a similar state and was preparing this particular action, what did I see next? What did I feel next? The answer becomes your experience. In other words, your brain combines information from outside and inside your head to produce everything you see, hear, smell, taste, and feel.
Here’s a quick demonstration that your memory is a critical ingredient in what you see. Take a look at the following three line drawings.
What do you see?
Excerpted from The Ultimate Droodles Compendium by Roger Price.
Inside your skull, without your awareness, billions of your neurons are trying to give these lines and blobs meaning. Your brain is searching through a lifetime of past experiences, issuing thousands of guesses at once, weighing probabilities, trying to answer the question What are these wavelengths of light most like? And it’s all happening faster than you can snap your fingers.
So what do you see? A bunch of black lines and a couple of blobs? Let’s see what happens when we give your brain some more information. Turn to pages 153–54 of the appendix, read the entry for line drawings, and then come back and look at the drawings again.
You should now see familiar objects instead of lines and blobs. Your brain is assembling memories from bits and pieces of past experiences to go beyond the visual data in front of you and make meaning. In the process, your brain is literally changing the firing of its own neurons. Objects that you might never have seen before now leap from the page. The lines and blobs haven’t changed—you have.
Artwork, particularly abstract art, is made possible because the human brain constructs what it experiences. When you view a cubist painting by Picasso and see recognizable human figures, that happens only because you have memories of human figures that help your brain make sense of the abstract elements. The painter Marcel Duchamp once said that an artist does only 50 percent of the work in creating art. The remaining 50 percent is in the viewer’s brain. (Some artists and philosophers call the second half “the beholder’s share.”)
Your brain actively constructs your experiences. Every morning, you wake up and experience a world around you full of sensations. You might feel the bedsheets against your skin. Maybe you hear sounds that woke you, like an alarm buzzing or birds chirping or your spouse snoring. Perhaps you smell coffee brewing. These sensations seem to sail right into your head as if your eyes, nose, mouth, ears, and skin were transparent windows on the world. But you don’t sense with your sensory organs. You sense with your brain.
What you see is some combination of what’s out there in the world and what’s constructed by your brain. What you hear is also some combination of what’s out there and what’s in your brain, and likewise for your other senses.
In much the same way, your brain also constructs what you feel inside your body. Your aches and jitters and other inner sensations are some combination of what’s going on in your brain and what’s actually happening within your lungs and heart and gut and muscles and so on. Your brain also adds information from your past experiences to guess what those sensations mean. For instance, when people haven’t slept enough and are fatigued or low energy, they may feel hungry (because they’ve been hungry before when their energy was low) and may think that a quick snack will boost their energy. In fact, they’re just tired from lack of sleep. This constructed experi
ence of hunger may be one reason why people gain unwanted weight.
Now we can unravel why our soldier friend saw guerrilla fighters instead of a shepherd boy with cows. His brain asked, Based on what I know about this war, and given that I am deep in the woods with my comrades, gripping a rifle, heart pounding, and there are moving figures ahead, and maybe something pointy, what am I likely to see next? And the result was Guerrilla fighters. In this situation, the stuff inside and outside his head didn’t match, and the inside stuff prevailed.
Most of the time when you look at cows, you see cows. But you’ve almost certainly had an experience like the soldier’s, where the information inside your head triumphs over the data from the outside world. Have you ever seen a friend’s face in a crowd, but when you looked again, you realized it was a different person? Have you ever felt your cell phone vibrate in your pocket when it didn’t? Have you ever had a song playing in your head that you couldn’t get rid of? Neuroscientists like to say that your day-to-day experience is a carefully controlled hallucination, constrained by the world and your body but ultimately constructed by your brain. It’s not the kind of hallucination that sends you to the hospital. It’s an everyday kind of hallucination that creates all your experiences and guides all your actions. It’s the normal way that your brain gives meaning to your sense data, and you’re almost always unaware that it’s happening.
I realize that this description defies common sense, but wait: there’s more. This whole constructive process happens predictively. Scientists are now fairly certain that your brain actually begins to sense the moment-to-moment changes in the world around you before those light waves, chemicals, and other sense data hit your brain. The same is true for moment-to-moment changes in your body—your brain begins to sense them before the relevant data arrives from your organs, hormones, and various bodily systems. You don’t experience your senses this way, but it’s how your brain navigates the world and controls your body.
Seven and a Half Lessons About the Brain Page 5