But don’t take my word for it. Instead, think of the last time you were thirsty and drank a glass of water. Within seconds after draining the last drops, you probably felt less thirsty. This event might seem ordinary, but water actually takes about twenty minutes to reach your bloodstream. Water can’t possibly quench your thirst in a few seconds. So what relieved your thirst? Prediction. As your brain plans and executes the actions that allow you to drink and swallow, it simultaneously anticipates the sensory consequences of gulping water, causing you to feel less thirsty long before the water has any direct effect on your blood.
Predictions transform flashes of light into the objects you see. They turn changes in air pressure into recognizable sounds, and traces of chemicals into smells and tastes. Predictions let you read the squiggles on this page and understand them as letters and words and ideas. They’re also the reason why it feels unsatisfying when a sentence is missing its final.
Scientists have had hints for more than a century that brains are predicting organs, though we didn’t decipher those hints until recently. You might have heard of Ivan Pavlov, the nineteenth-century physiologist who famously taught his dogs to salivate upon hearing a sound (usually described as a bell, but it was really a ticking metronome). Pavlov played that sound right before his dogs ate each meal, and eventually the dogs salivated when they heard the sound even when they weren’t fed. Pavlov won a Nobel Prize for discovering this effect, which became known as Pavlovian or classical conditioning, but he didn’t realize that he was discovering how brains predict. His dogs were not reacting to the sound by drooling. Their brains were predicting the experience of eating food and preparing their bodies in advance to consume it.
You can try a similar experiment right now. Picture your favorite food in your mind. (For me, it’s a morsel of dark chocolate with sea salt.) Imagine its smell, its taste, and how it feels in your mouth. Are you salivating yet? I am, just writing this, and no metronome is required. If neuroscientists were scanning my brain right now, they might see increased activity in regions that are important for the sense of taste and smell and in regions that control salivation.
If this demonstration made you smell or taste your favorite food or made your mouth water even a bit, then you successfully changed the firing of your own neurons in exactly the same way that automatic predictions do. This process is similar to what happened when you looked at the three drawings earlier. In both cases, I used deliberate, contrived examples to reveal what your brain does naturally and automatically.
In a very real sense, predictions are just your brain having a conversation with itself. A bunch of neurons make their best guess about what will happen in the immediate future based on whatever combination of past and present that your brain is currently conjuring. Those neurons then announce that guess to neurons in other brain areas, changing their firing. Meanwhile, sense data from the world and your body injects itself into the conversation, confirming (or not) the prediction that you’ll experience as your reality.
In actuality, your brain’s predictive process is not quite so linear. Usually your brain has several ways to deal with a given situation, and it creates a flurry of predictions and estimates probabilities for each one. Is that rustling sound in the forest due to the wind, an animal, an enemy fighter, or a shepherd? Is that long, brown shape a branch, a staff, or a rifle? Ultimately, in each moment, some prediction is the winner. Often, it’s the prediction that best matches the incoming sense data, but not always. Either way, the winning prediction becomes your action and your sensory experience.
So, your brain issues predictions and checks them against the sense data coming from the world and your body. What happens next still astounds me, even as a neuroscientist. If your brain has predicted well, then your neurons are already firing in a pattern that matches the incoming sense data. That means this sense data itself has no further use beyond confirming your brain’s predictions. What you see, hear, smell, and taste in the world and feel in your body in that moment are completely constructed in your head. By prediction, your brain has efficiently prepared you to act.
Here’s what I mean. Suppose when the soldier’s brain predicted a line of guerrilla fighters up ahead, the fighters were actually there. From his brain’s perspective, the real fighters confirmed the prediction, because his brain had already constructed the sights, sounds, and smells of the fighters, adjusted his body budget, and prepared his body to act. In this case, his predictions prepared him to raise his rifle and shoot.
But in the real story, the soldier’s brain made the wrong prediction. It predicted a posse of guerrilla fighters with machine guns when really he faced a shepherd boy with a herding staff and a bunch of cattle. In that situation, his brain had two options. One option was to incorporate the sense data from the outside world, update his predictions, and construct a new, corrected experience of a boy and his cows. This new prediction would seed the soldier’s brain and improve prediction next time. Scientists have a fancy name for this option. We call it “learning.”
The soldier’s brain chose the other option, however; his brain stuck with its prediction in spite of the sense data from the world. This can happen for many reasons, one being that his brain predicted his life was on the line. Brains aren’t wired for accuracy. They’re wired to keep us alive.
When your predicting brain is right, it creates your reality. When it’s wrong, it still creates your reality, and hopefully it learns from its mistakes. It’s fortunate that the soldier’s friend tapped him on the shoulder, prompting him to look again and allowing his brain to launch new predictions.
Now here’s the final nail in the coffin of common sense: All this predicting happens backward from the way we experience it. You and I seem to sense first and act second. You see an enemy and then raise your rifle. But in your brain, sensing actually comes second. Your brain is wired to prepare for action first, like moving your index finger onto a trigger and making body-budgeting changes to support that movement. It’s also wired to route these predictions to your sensory systems, which predict the feeling of cold steel on your fingertip and your racing heartbeat. In the case of our soldier friend, his brain heard rustling leaves, moved his hands on the gun, and guided itself to see enemies that weren’t present.
Yes, your brain is wired to initiate your actions before you’re aware of them. That is kind of a big deal. After all, in everyday life, you do many things by choice, right? At least it seems that way. For example, you chose to open this book and read these words. But the brain is a predicting organ. It launches your next set of actions based on your past experience and current situation, and it does so outside of your awareness. In other words, your actions are under the control of your memory and your environment. Does this mean you have no free will? Who’s responsible for your actions?
Philosophers and other scholars have debated the existence of free will pretty much since the invention of philosophy. It’s not likely that we will settle that debate here. Nevertheless, we can highlight a piece of the puzzle that is often ignored.
Think about the last time you acted on autopilot. Maybe you bit your nails. Maybe your brain-to-mouth connection was too well oiled and you muttered something regrettable to a friend. Maybe you looked away from an engaging movie and discovered that you’d downed an entire jumbo bag of red Twizzlers. In these moments, your brain employed its predictive powers to launch your actions, and you had no feeling of agency. Could you have exercised more control and changed your behavior in the moment? Maybe, but it would have been difficult. Were you responsible for these actions? More than you might think.
The predictions that initiate your actions don’t appear out of nowhere. If you hadn’t chomped on your nails as a kid, you probably wouldn’t bite them now. If you’d never learned the regrettable words you tossed at your friend, you couldn’t say them now. If you’d never developed a taste for licorice . . . you get the idea. Your brain predicts and prepares your actions using your past experien
ces. If you could magically reach back in time and change your past, your brain would predict differently today, and you might act differently and experience the world differently as a result.
It’s impossible to change your past, but right now, with some effort, you can change how your brain will predict in the future. You can invest a little time and energy to learn new ideas. You can curate new experiences. You can try new activities. Everything you learn today seeds your brain to predict differently tomorrow.
Here’s an example. All of us have had a nervous feeling before a test, but for some people, this anxiety is crippling. Based on their past experiences of taking tests, their brains predict and launch a hammering heartbeat and sweaty hands and they’re unable to complete the test. If this happens enough, they fail courses or even drop out of school. But here’s the thing: a hammering heartbeat is not necessarily anxiety. Research shows that students can learn to experience their physical sensations not as anxiety but as energized determination, and when they do, they perform better on tests. That determination seeds their brains to predict differently in the future so they can get their butterflies flying in formation. If they practice this skill enough, they can pass a test, perhaps pass their courses, and even graduate, which has a huge impact on their future earning potential.
It’s also possible to change predictions to cultivate empathy for other people and act differently in the future. An organization called Seeds of Peace tries to change predictions by bringing together young people from cultures that are in serious conflict, like Palestinians and Israelis, and Indians and Pakistanis. The teens participate in activities like soccer, canoeing, and leadership training, and they can talk about the animosity between their cultures in a supportive environment. By creating new experiences, these teens are changing their future predictions in the hopes of building bridges between the cultures and, ultimately, creating a more peaceful world.
You can try something similar on a smaller scale. Today, many of us feel like we live in a highly polarized world, where people with opposing opinions cannot even be civil to each other. If you want things to be different, I offer you a challenge. Pick a controversial political issue that you feel strongly about. In the United States, that might be abortion, guns, religion, the police, climate change, reparations for slavery, or perhaps a local issue that’s important to you. Spend five minutes per day deliberately considering the issue from the perspective of those you disagree with, not to have an argument with them in your head, but to understand how someone who’s just as smart as you can believe the opposite of what you do.
I’m not asking you to change your mind. I’m also not saying this challenge is easy. It requires a withdrawal from your body budget, and it might feel pretty unpleasant or even pointless. But when you try, really try, to embody someone else’s point of view, you can change your future predictions about the people who hold those different views. If you can honestly say, “I absolutely disagree with those people, but I can understand why they believe what they do,” you’re one step closer to a less polarized world. This is not magical liberal academic rubbish. It’s a strategy that comes from basic science about your predicting brain.
Everyone who’s ever learned a skill, whether it’s driving a car or tying a shoe, knows that things that require effort today become automatic tomorrow with enough practice. They’re automatic because your brain has tuned and pruned itself to make different predictions that launch different actions. As a consequence, you experience yourself and the world around you differently. That is a form of free will, or at least something we can arguably call free will. We can choose what we expose ourselves to.
My point here is that you might not be able to change your behavior in the heat of the moment, but there’s a good chance you can change your predictions before the heat of the moment. With practice, you can make some automatic behaviors more likely than others and have more control over your future actions and experiences than you might think.
I don’t know about you, but I find this message hopeful, even though, as you might suspect, this extra bit of control comes with some fine print. More control also means more responsibility. If your brain doesn’t merely react to the world but actively predicts the world and even sculpts its own wiring, then who bears responsibility when you behave badly? You do.
Now, when I say responsibility, I’m not saying people are to blame for the tragedies in their lives or the hardships they experience as a result. We can’t choose everything that we’re exposed to. I’m also not saying that people with depression, anxiety, or other serious illnesses are to blame for their suffering. I’m saying something else: Sometimes we’re responsible for things not because they’re our fault, but because we’re the only ones who can change them.
When you were a child, your caregivers tended the environment that wired your brain. They created your niche. You didn’t choose that niche—you were a baby. So you’re not responsible for your early wiring. If you grew up around people who, say, were very similar to one another, wearing the same types of clothing, agreeing on certain beliefs, practicing the same religion, or having a narrow range of skin tones or body shapes, these sorts of similarities tuned and pruned your brain to predict what people are like. Your developing brain was handed a trajectory.
Things are different after you grow up. You can hang out with all kinds of people. You can challenge the beliefs that you were swaddled in as a child. You can change your own niche. Your actions today become your brain’s predictions for tomorrow, and those predictions automatically drive your future actions. Therefore, you have some freedom to hone your predictions in new directions, and you have some responsibility for the results. Not everyone has broad choices about what they can hone, but everyone has some choice.
As the owner of a predicting brain, you have more control over your actions and experiences than you might think and more responsibility than you might want. But if you embrace this responsibility, think about the possibilities. What might your life be like? What kind of person might you become?
Lesson No.
5
Your Brain Secretly Works with Other Brains
WE HUMANS ARE a social species. We live in groups. We take care of one another. We build civilizations. Our ability to cooperate has been a major adaptive advantage. It has allowed us to colonize virtually every habitat on Earth and survive and thrive in more climates than any other animal, except maybe bacteria.
Part of being a social species, it turns out, is that we regulate one another’s body budgets—the ways in which our brains manage the bodily resources we use every day. You’ve already learned how caregivers help their babies’ brains to budget these resources efficiently (or badly, in the case of the Romanian orphans) as those little brains wire themselves to their world. Well, the mutual body budgeting and rewiring continue long after those little brains are grown. For your whole life, outside of your awareness, you make deposits of a sort into other people’s body budgets, as well as withdrawals, and others do the same for you. This ongoing undercover operation has pros and cons with profound implications for how we live our lives.
How do the people around you influence your body budget and rewire your adult brain? Remember that your brain changes its own wiring after new experiences, a process called plasticity. Microscopic parts of your neurons change gradually every day through tuning and pruning. For example, branch-like dendrites become bushier, and their associated neural connections become more efficient. This remodeling job requires energy from your body budget, so your predicting brain needs a good reason to splurge. And a great reason is that the connections are used frequently to deal with the people around you. Little by little, your brain becomes tuned and pruned as you interact with others.
Some brains are more attentive to the people around them, and others less so, but everybody has somebody. (Even psychopaths are dependent on other people, just in a really unfortunate way.) Ultimately, your family, friends, neighbors
, and even strangers contribute to your brain’s structure and function and help your brain keep your body humming along.
This co-regulation has measurable effects. Changes in one person’s body often prompt changes in another person’s body, whether the two are romantically involved, just friends, or strangers meeting for the first time. When you’re with someone you care about, your breathing can synchronize, as can the beating of your hearts, whether you’re in casual conversation or a heated argument. This sort of physical connection happens between infants and their caregivers, between therapists and their clients, and among people taking a yoga class or singing in a choir together. We often mirror each other’s movements in a dance that neither of us is aware of and that is choreographed by our brains. One of us leads, the other follows, and sometimes we switch. In contrast, when we don’t like or trust each other, our brains are like dance partners who step on each other’s toes.
We also adjust each other’s body budgets by our actions. If you raise your voice, or even your eyebrow, you can affect what goes on inside other people’s bodies, such as their heart rate or the chemicals carried in their bloodstream. If your loved one is in pain, you can lessen her suffering merely by holding her hand.
Being a social species has all sorts of advantages for us Homo sapiens. One advantage is that we live longer if we have close, supportive relationships with other people. It may seem obvious that loving relationships are good for us, but studies show that the benefits go beyond what common sense would suggest. If you and your partner feel that your relationship is intimate and caring, that you’re responsive to each other’s needs, and that life seems easy and enjoyable when you’re together, both of you are less likely to get sick. If you’re already sick with a serious illness, such as cancer or heart disease, you’re more likely to get better. These studies were conducted on married couples, but the results appear to hold for close friendships too, and even for pet owners.
Seven and a Half Lessons About the Brain Page 6