Lisa Feldman Barrett. Seven and a Half Lessons about the Brain (2020)
In a paragraph
The primary function of the brain is to manage the body budget. All vertebrates brains are similar in sharing a common brain manufacturing plan. Brains develop in a niche by tuning and pruning. Perception is a predictive construction. Creating social reality is a human speciality.
Key points
- The brain’s most important job is to control the body, to run the body budget for a little worm body that has evolved to be complex.
- We have one brain not three – the Triune Brain model is wrong. All vertebrates have a common brain manufacture plan, differing only in the time on each phase. The human cortex is not unusually large. Natural selection did not aim itself toward us—we’re just an interesting sort of animal with particular adaptations.
- A brain is a network. Its complexity allows many formations. Degeneracy allows the same actions and experiences to be created by different neurons.
- Little brains wire themselves to their niche by tuning and pruning. We have the kind of nature that requires nurture.
- 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. And, what’s more, this construction is predictive.
- You might not be able to change your behaviour in the heat of the moment, but you can change your niche and yourself over time.
- As a social species we regulate one another’s body budgets – including through words. Chronic social stress is damaging. Personal freedoms should be balanced against impact on others.
- Affect is like a barometer of how you are doing, of your body budget.
- Social reality is a superpower that emerges from an ensemble of human brains. It gives us the possibility to create our destiny by making up abstract concepts, sharing them and weaving them into a reality.
Comments
The author is a Professor of Psychology, and this book sets out key ideas about the brain for a lay audience. Although the book is fairly short, it is dense with important ideas, all presented clearly and engagingly with many fine turns of phrase.
There are no footnotes in the text, but comments are provided in an appendix and more extensive notes and references are included in a dedicated website for the book. This arrangement is well done and is a model for how to combine accessible text with more academic detail. I also recommend the Audible book read by the author.
Links
EXTRACTS
Author’s Note
I wrote this book of short, informal essays to intrigue and entertain you. It’s not a full tutorial on brains. Each essay presents a few compelling scientific nuggets about your brain and considers what they might reveal about human nature.
Why are there seven and a half lessons rather than eight? The opening essay tells a story of how brains evolved, but it is just a brief peek into a vast evolutionary history—hence, half a lesson. The concepts that it introduces are critical to the rest of the book.
The Half-Lesson: Your Brain Is Not for Thinking
Running a body requires biological resources. Every action you take (or don’t take) is an economic choice—your brain is guessing when to spend resources and when to save them.
When it came to body budgeting, prediction beat reaction. The scientific name for body budgeting is allostasis. It means automatically predicting and preparing to meet the body’s needs before they arise. As animals gradually evolved bigger bodies with more systems to maintain, their handful of body-budgeting cells also evolved to become brains of greater and greater complexity. Your body budget is like thousands of financial accounts in a giant, multinational corporation, and you have a brain that’s up to the task.
Your brain’s most important job is to control your body—to manage allostasis—by predicting energy needs before they arise so you can efficiently make worthwhile movements and survive. Your brain continually invests your energy in the hopes of earning a good return, such as food, shelter, affection, or physical protection, so you can perform nature’s most vital task: passing your genes to the next generation. Your brain’s most important job is not thinking. It’s running a little worm body that has become very, very complicated.
You and I do not experience our every thought, every feeling of happiness or anger or awe, every hug we give or receive, every kindness we extend, and every insult we bear as a deposit or withdrawal in our metabolic budgets, but under the hood, that is what’s happening. This idea is key to understanding how your brain works
Lesson No. 1: You Have One Brain (Not Three)
Plato’s compelling morality tale of inner conflict remains one of the most cherished narratives in Western civilization. Paul MacLeans’ triune brain – lizard brain, limbic system, neocortex.
We now know that reptiles and nonhuman mammals have the same kinds of neurons that humans do. The common brain-manufacturing plan begins shortly after conception, when an embryo starts producing neurons. The neurons that form a mammal’s brain are created in an astonishingly predictable order. If the brains of so many vertebrates develop in the same order, why do these brains look so different from one another? Because the manufacturing process runs in stages, and the stages last for shorter or longer durations in different species.
Our cortex is just a scaled-up version of the relatively smaller cortex found in relatively smaller-brained monkeys, chimps, and many carnivores. It’s also a scaled-down version of the larger cortex found in the larger brains of elephants and whales.
Western scientists and intellectuals concocted the idea of the big, rational cortex and have kept it alive for many years. The real story is that during the course of evolution, certain genes mutated to cause particular stages of brain development to run for longer or shorter times, producing a brain with proportionally bigger or smaller parts.
Natural selection did not aim itself toward us—we’re just an interesting sort of animal with particular adaptations that helped us survive and reproduce in particular environments. To believe in the triune brain is to award ourselves a first prize trophy for Best Species.
Sometimes emotion is rational, like when you feel afraid because you’re in imminent danger. And sometimes thinking isn’t rational, like when you scroll through social media. What we call mental illnesses may be rational body-budgeting for the short term that’s out of sync.
Lesson No. 2: Your Brain Is a Network
We are surrounded by so-called facts about the brain that are just metaphors. Metaphors produce the illusion of knowledge and must be used with care. But a brain network is not a metaphor but a concept. It’s a description that comes from the best available science about how brains evolved, how they’re structured, and how they function.
Your brain is a network of 128 billion neurons connected as a single, massive, and flexible structure. Network thinking captures much of the brain’s dynamic behaviour—slow changes by plasticity, faster changes by neurotransmitters and neuromodulators, and the flexibility of neurons with multiple jobs. Brain hubs, like airport hubs, make a complicated system efficient. Any neuron can do more than one thing. Degeneracy in the brain means that your actions and experiences can be created in multiple ways.
Complexity empowers a brain to act flexibly in all kinds of situations. Complexity means your brain can create massive numbers of different patterns by combining bits and pieces of old patterns it has made before. A system has higher or lower complexity depending on how much information it can manage by reconfiguring itself.
Brains of higher complexity can remember more. A brain doesn’t store memories like files in a computer—it reconstructs them on demand with electricity and swirling chemicals. We call this process remembering but it’s really assembling. A complex brain can assemble many more memories than either Meatloaf Brain or Pocketknife Brain could. And each time you have the same memory, your brain may have assembled it with a different collection of neurons.
Lesson No. 3: Little Brains Wire Themselves to Their World
Tuning and pruning. Tuning means that the branch-like dendrites become bushier. It also means that the trunk-like axon develops a thicker coating of myelin. “Neurons that fire together, wire together.” Meanwhile, less-used connections weaken and die off. This is the process of pruning, the neural equivalent of “If you don’t use it, you lose it.” Pruning is critical in a developing brain, because little humans are born with many more connections than they will ultimately use. A human embryo creates twice as many neurons as an adult brain needs, and infant neurons are quite a bit bushier than neurons in an adult brain. Your bushy dendrites keep sprouting new buds, and your brain tunes and prunes them and buds that aren’t tuned disappear within a couple of days.
Caregivers regulate the baby’s physical environment and therefore her body budget. They also guide attention to things of interest. Newborn brains don’t know what’s important and what’s not, so they cannot focus as adults do. They still lack the wiring that narrows their lantern into a spotlight of attention. Little brains require a social world to develop.
Every animal has a niche, and it creates that niche as it senses the world, makes worthwhile movements, and regulates its body budget.
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. 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.
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.
Lesson No. 4: Your Brain Predicts (Almost) Everything You Do
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. 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.
Artwork, particularly abstract art, is made possible because the human brain constructs what it experiences. “The beholder’s share.”
Your brain also constructs what you feel inside your body. It 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.
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. The soldier’s 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.
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. I realize that this description defies common sense, but wait: there’s more. This whole constructive process happens predictively.
Water can’t possibly quench your thirst in a few seconds. So what relieved your thirst? Prediction. Pavlov’s 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.
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. 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. Your brain is wired to initiate your actions before you’re aware of them.
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.
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.
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.
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. 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.
Lesson No. 5: Your Brain Secretly Works with Other Brains
Part of being a social species, it turns out, is that we regulate one another’s body budgets. 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.
Being a social species is good for us, but there are also disadvantages. We may be healthier and live longer if we have close relationships, but we also get sick and die earlier when we persistently feel lonely—possibly years earlier, based on the data. Without someone else helping to regulate our body budgets, we bear an extra burden. Have you ever lost someone close to you and felt like you’d lost a part of yourself? That’s because you did. You lost a source of keeping your bodily systems in balance.
Humans are unique in the animal kingdom, however, because we also regulate each other with words.
Evolution gifted you with a nervous system that can cope with temporary metabolic changes and even benefit from them. Occasional stress can be like exercise. But if you are stressed over and over and over again, without much opportunity to recover, the effects can be far more grave. One study found that if you’re exposed to social stress within two hours of a meal, your body metabolizes the food in a way that adds 104 calories to the meal.
The best thing for your nervous system is another human. The worst thing for your nervous system is also another human. This situation leads us to a fundamental dilemma of the human condition. Your brain needs other people in order to keep your body alive and healthy, and at the same time, many cultures strongly value individual rights and freedoms. Dependence and freedom are naturally in conflict. How, then, can we best respect and cultivate individual rights when we are social animals who regulate one another’s nervous systems to survive? Like it or not, we influence the brains and bodies of those around us with our actions and words, and they return the favour.
Lesson No. 6: Brains Make More than One Kind of Mind
It’s important for humans to have many kinds of minds, because variation is critical for the survival of a species.
An especially useful feature of the mind, and one of the closest things we have to a universal mental feature, is mood—the general sense of feeling that comes from your body. Scientists call it affect. Feelings of affect range from pleasant to unpleasant, from idle to activated. Affect is not emotion; your brain produces affect all the time, whether you’re emotional or not and whether you notice it or not. Affect is the source of all your joys and sorrows. It makes some things profound or sacred to you and other things trivial or vile.
Where does affect come from? In every moment—like right now, as you read these words—your hormones, organs, and immune system are producing a storm of sense data, and you’re barely aware of it. You notice your heartbeat and breathing only when they’re intense or you focus on them. You almost never notice your body temperature unless it’s too high or too low. Your brain, however, makes meaning from this data storm continuously to predict your body’s next action and meet its metabolic needs before they arise. In the midst of all this activity inside you, something miraculous happens. Your brain summarizes what’s going on with your body in the moment, and you feel that summary as affect. Affect is like a barometer for how you’re doing. Remember, your brain is constantly running a budget for your body. Affect hints at whether your body budget is in balance or in the red. Unfortunately, affect is not as precise as a meter. It just tells you, Beep! You feel like crap. Then your brain must predict what to do next to keep you alive and well. Scientists are still puzzling out how your brain’s body-budgeting activities, which are physical, become transformed into affect, which is mental.
Your kind of mind is just one among many, and you are not stuck with the mind you have. You can modify your mind. People do this all the time. And can move to different cultures – acculturation.
When it comes to human minds, variation is the norm, and what we call “human nature” is really many human natures. We don’t need one universal mind in order to claim that we are all one species. All we need is an exceptionally complex brain that wires itself to its physical and social surroundings.
Lesson No. 7: Our Brains Can Create Reality
Most of your life takes place in a made-up world. You actively and willingly participate in this made-up world every day. It is real to you. It’s as real as your own name, which, by the way, was also made up by people. We all live in a world of social reality that exists only inside our human brains. The Earth itself, with its rocks and trees and deserts and oceans, is physical reality. Social reality means that we impose new functions on physical things, collectively.
You and I can create social reality with other people without even trying, because we have human brains. To the best of our knowledge, no other animal brain can do that—social reality is a uniquely human ability. Scientists don’t know for sure how our brains developed this capacity, but we suspect it has something to do with a suite of abilities that I’ll call the Five Cs: creativity, communication, copying, cooperation, and compression.
The wiring of your cerebral cortex makes compression possible. Compression enables sensory integration. Sensory integration enables abstraction. Abstraction permits your highly complex brain to issue flexible predictions based on the functions of things rather than on their physical form. That is creativity. And you can share these predictions by way of communication, cooperation, and copying. That is how the Five Cs empower a human brain to create and share social reality.
Most animals have evolutionary adaptations that make them specialists in their niches. But humans became generalists; evolution blended the Five Cs into a potion that spurs us to bend the world to our will. All animal brains pay attention to things in their physical environment that are relevant to their well-being and survival and ignore the other stuff. But humans don’t just select stuff from the physical world to create our niche. We add to the world by collectively imposing new functions, and we live by them. Social reality is human niche construction. Social reality is an incredible gift. You can simply make stuff up, like a meme or a tradition or a law, and if other people treat it as real, it becomes real. Our social world is a buffer we build around the physical world. But the human brain misunderstands itself and mistakes social reality for physical reality, which can cause all sorts of problems.
Social reality is a superpower that emerges from an ensemble of human brains. It gives us the possibility to chart our own destiny and even influence the evolution of our species. We can make up abstract concepts, share them, weave them into a reality, and conquer just about any environment—natural, political, or social—as long as we work together. We have more control over reality than we might think. We also have more responsibility for reality than we might realize.
Appendix: The Science Behind the Science
This appendix adds crucial scientific details for certain topics in my essays, explains that certain points are still debated by scientists, and gives credit to scientists whose ideas and turns of phrase I’ve incorporated. Full references for the book can be found at sevenandahalflessons.com. The biggest challenge of science writing is deciding what to leave out.