Seven And A Half Lessons About The Brain - Lisa Feldman Barrett

Last updated Apr 18, 2024

• Author: Lisa Feldman Barrett
• Full Title: Seven And A Half Lessons About The Brain
• Category: #books

The essays don’t tell you what to think about human nature, but they do invite you to think about the kind of human you are or want to be. (Location 50)

Amphioxi are your distant cousins, and they’re still around today. (Location 60)

the idea that our brains evolved for thinking has been the source of many profound misconceptions about human nature. (Location 70)

Both predators and prey evolved to sense more of the world around them. (Location 80)

Energy efficiency was a key to survival. (Location 93)

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. (Location 97)

When it came to body budgeting, prediction beat reaction. (Location 102)

allostasis. It means automatically predicting and preparing to meet the body’s needs before they arise. (Location 109)

All sorts of animals, including humans, somehow conjure up past experiences to prepare their bodies for action. (Location 114)

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. (Location 128)

evolution does not act with purpose— ​ there is no “why.” (Location 135)

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. (Location 138)

all of these mental capacities are consequences of a central mission to keep you alive and well by managing your body budget. Everything your brain creates, from memories to hallucinations, from ecstasy to shame, is part of this mission. (Location 142)

Plato’s compelling morality tale of inner conflict remains one of the most cherished narratives in Western civilization. (Location 164)

According to this evolutionary story, the human brain ended up with three layers ​— ​ one for surviving, one for feeling, and one for thinking ​— ​ an arrangement known as the triune brain. (Location 169)

The triune brain idea is one of the most successful and widespread errors in all of science. (Location 181)

Bad behavior doesn’t come from ancient and unbridled inner beasts. Good behavior is not the result of rationality. And rationality and emotion are not at war . . . (Location 186)

By the 1990s, experts had completely rejected the idea of a three-layered brain. It simply didn’t hold up when they analyzed neurons with more sophisticated tools. (Location 202)

In MacLean’s day, scientists compared one animal brain to another by injecting them with dye, slicing them paper-thin like deli meat, and squinting at the stained slices through a microscope. (Location 204)

This arrangement among brain regions ​— ​ segregating and then integrating ​— ​ creates a more complex brain that can control a larger and more complex body. (Location 220)

The neurons that form a mammal’s brain are created in an astonishingly predictable order. The ordering holds true for mice, rats, dogs, cats, horses, anteaters, humans, and every other mammalian species studied so far, and genetic evidence strongly suggests the order holds for reptiles, birds, and some fish. (Location 232)

the manufacturing process runs in stages, and the stages last for shorter or longer durations in different species. The biological building blocks are the same; what differs is the timing. (Location 236)

All mammals have a relatively big cortex in a brain that’s relatively large for their body size. (Location 253)

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. (Location 260)

other animals have evolved abilities that surpass ours in significant ways. (Location 269)

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. Other animals are not inferior to humans. They are uniquely and effectively adapted to their environments. (Location 272)

Your brain is not more evolved than a rat or lizard brain, just differently evolved. (Location 274)

To believe in the triune brain is to award ourselves a first prize trophy for Best Species. (Location 279)

If you choose not to act rationally, then your behavior may be called immoral, and if you’re unable to act rationally, you are considered mentally ill. (Location 282)

sometimes thinking isn’t rational, like when you scroll through social media for hours, telling yourself you’re bound to come across something important. (Location 285)

Perhaps rationality is better defined in terms of the brain’s most important job: body budgeting (Location 286)

What we call mental illnesses, then, may be rational body-budgeting for the short term that’s out of sync with the immediate environment, the needs of other people, or your own best interests down the road. (Location 300)

Many other social institutions are steeped in the idea of a mind at war with itself. (Location 308)

You have one brain, not three. To move past Plato’s ancient battle, we might need to fundamentally rethink what it means to be rational, what it means to be responsible for our actions, and perhaps even what it means to be human. (Location 312)

Today, we remain surrounded by so-called facts about the brain that are also just metaphors. (Location 320)

a network of 128 billion neurons connected as a single, massive, and flexible structure. A brain network (Location 334)

Your neurons never just sit around waiting for something in the outside world to make them fire. Instead, all of your neurons chat constantly with one another through their wiring. (Location 346)

Communication in your brain is a balancing act between speed and cost. Each neuron directly passes information to just a few thousand other neurons and receives information from a few thousand others, give or take, yielding over five hundred trillion neuron-to-neuron connections. (Location 349)

Brain hubs, like airport hubs, make a complicated system efficient. They allow most neurons to participate globally even as they focus more locally. (Location 364)

Hubs are points of vulnerability because they are points of efficiency (Location 370)

some of these chemicals, such as serotonin and dopamine, can also act on other neurotransmitters to dial up or dial down their effects. When brain chemicals act in this way, we call them neuromodulators. (Location 378)

Neuromodulators and neurotransmitters together allow your brain’s single structure to take on trillions of different patterns of activity. (Location 380)

if you blindfold people with typical vision for a few days and teach them to read braille, neurons in their visual cortex become more devoted to the sense of touch. Remove the blindfold, and the effect disappears after twenty-four hours. (Location 388)

Even a simple reaching action like this, when done more than once, can be guided by different sets of neurons. This phenomenon is called degeneracy. Scientists suspect that all biological systems have degeneracy. (Location 400)

Degeneracy in the brain means that your actions and experiences can be created in multiple ways. (Location 405)

complexity. It is a brain’s ability to configure itself into an enormous number of distinct neural patterns. (Location 409)

Complexity empowers a brain to act flexibly in all kinds of situations. (Location 414)

Complexity also helps us contemplate the whole world beyond our immediate surroundings, even outer space, and care about the past and the future to an extent that other animals do not. (Location 416)

Complexity means your brain can create massive numbers of different patterns by combining bits and pieces of old patterns it has made before. (Location 420)

when existing brain parts become more flexible, the result is much more complexity than we get by accumulating new parts. (Location 441)

it reconstructs them on demand with electricity and swirling chemicals. We call this process remembering but it’s really assembling. (Location 444)

Brains of higher complexity are also more creative. (Location 447)

Intelligent behavior has emerged many times in different species with differently structured brains. (Location 455)

The highly complex human brain isn’t a pinnacle of evolution, remember; it’s just well adapted to the environments we inhabit. (Location 457)

Metaphors are wonderful for explaining complex topics in simple, familiar terms. A metaphor’s simplicity, however, can become its greatest failing if people treat the metaphor as an explanation. (Location 472)

Metaphors provide the illusion of knowledge, so they must be used with care. (Location 476)

Your brain is more than just neurons. It includes blood vessels and various fluids that I haven’t talked about. It also includes other kinds of brain cells, called glial cells, that function in ways that scientists don’t fully understand yet. Your brain network may even extend, surprisingly, into your gut and intestines, where scientists have found microbes that communicate with your brain via neurotransmitters. (Location 478)

Many animals emerge from the egg or womb with brains that are more fully wired to control their bodies, but little human brains are born under construction. (Location 488)

To a remarkable extent, a baby’s genes are guided and regulated by the surrounding environment. (Location 496)

A baby’s wiring instructions come not only from the physical environment but also from the social environment, from caregivers and people like you and me. (Location 502)

Genes play a key role in building a baby’s brain wiring, and they also open the door for us to wire her newborn brain in the context of her culture. (Location 506)

As information travels from the world into the newborn brain, some neurons fire together more frequently than others, causing gradual brain changes that we’ve called plasticity. These changes nudge the infant’s brain toward higher complexity via two processes we’ll call tuning and pruning. (Location 507)

Tuning means strengthening the connections between neurons, (Location 510)

less-used connections weaken and die off. This is the process of pruning, (Location 516)

Pruning is critical in a developing brain, because little humans are born with many more connections than they will ultimately use. (Location 517)

Buds that aren’t tuned disappear within a couple of days. (Location 524)

If caregivers do these activities effectively, the baby’s brain is free to tune and prune itself to perform healthy body budgeting. (Location 532)

Little brains are also wired by what caregivers don’t do. (Location 536)

When an infant is crying for a long time and you don’t check in regularly, her brain may learn that the world is unreliable and unsafe while her body budget goes untended. (Location 537)

In general, toddlers learn to tend their own body budgets better when their caregivers create learning opportunities for them instead of hovering and taking care of their every need. (Location 541)

“cocktail party effect.”) Your adult brain can effortlessly focus on one thing and ignore others, (Location 545)

the newborn brain doesn’t have a spotlight. It has more of a lantern, illuminating a wide area in its physical environment. Newborn brains don’t know what’s important and what’s not, so they cannot focus as adults do. (Location 549)

The mother’s speech and the back-and-forth switching of gaze, which scientists call sharing attention, alert the baby that the toy dog is significant (Location 553)

its own environment of what is relevant to its body budget and what can be ignored. Scientists call this environment a niche. (Location 556)

Every animal has a niche, and it creates that niche as it senses the world, makes worthwhile movements, and regulates its body budget. (Location 557)

Your niche extends far beyond your immediate surroundings to include events around the world, past, present, and future. (Location 558)

After months of practice sharing attention with caregivers, an infant will learn to elicit shared attention from them. (Location 560)

If you heard only one language as a baby, you’d need to relearn the ability to hear and distinguish sounds outside your language, which is hard. (Location 571)

When you were a baby, you learned to recognize the people around you. Your infant brain was tuned and pruned to detect fine differences in their faces so you could tell them apart. (Location 572)

you can quickly retune your brain and restore this ability by looking at lots of diverse faces; it’s much easier than retuning to the sounds of a foreign language. (Location 576)

when you kiss someone, you are enveloped in a unified experience that combines the sight of a face, the sound of breathing, the feel, taste, and scent of luscious lips, and the racing of your heart. Your brain assembles these sensations into a cohesive whole. Scientists call this process sensory integration. (Location 578)

Sensory integration itself is tuned and pruned as babies grow. (Location 581)

A newborn at first can’t recognize his mother by her face, because he hasn’t learned what a face is, and his visual system isn’t fully formed. He might know a bit about how his mother sounds, and he can smell her breast milk. (Location 581)

Sensory integration conjures his first feeling of trust. It’s part of the neural foundation for attachment. (Location 585)

Little brains require a social world in order to develop typically. (Location 588)

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. (Location 590)

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. (Location 600)

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. (Location 604)

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. (Location 608)

When children are persistently neglected, in all likelihood they’ll suffer ill effects eventually. (Location 609)

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. (Location 612)

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. (Location 618)

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. (Location 620)

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. (Location 626)

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. (Location 627)

Recent estimates suggest that it’s far cheaper to eradicate poverty than to deal with its effects decades later. (Location 631)

guess based on evidence from evolutionary biology and anthropology: This arrangement helps our cultural and social knowledge flow efficiently from generation to generation. (Location 637)

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. (Location 640)

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, (Location 641)

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. (Location 644)

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. (Location 649)

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. (Location 664)

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. (Location 674)

Your brain assembles these bits into memories to infer the meaning of the sense data and guess what to do about it. (Location 679)

Your past experiences include not only what happened in the world around you but also what happened inside your body. (Location 680)

your brain combines information from outside and inside your head to produce everything you see, hear, smell, taste, and feel. (Location 687)

The Ultimate Droodles Compendium by Roger Price (Location 691)

Artwork, particularly abstract art, is made possible because the human brain constructs what it experiences. (Location 700)

you don’t sense with your sensory organs. You sense with your brain. (Location 707)

Your brain also adds information from your past experiences to guess what those sensations mean. (Location 711)

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. (Location 722)

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 (Location 726)

the winning prediction becomes your action and your sensory experience. (Location 756)

your brain issues predictions and checks them against the sense data coming from the world and your body. (Location 757)

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. (Location 758)

Brains aren’t wired for accuracy. They’re wired to keep us alive. (Location 770)

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, (Location 774)

your brain is wired to initiate your actions before you’re aware of them. (Location 778)

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. (Location 793)

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. (Location 798)

It’s also possible to change predictions to cultivate empathy for other people and act differently in the future. (Location 802)

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. (Location 802)

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. (Location 805)

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. (Location 810)

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. (Location 817)

We can choose what we expose ourselves to. (Location 819)

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. (Location 820)

Sometimes we’re responsible for things not because they’re our fault, but because we’re the only ones who can change them. (Location 828)

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. (Location 833)

Not everyone has broad choices about what they can hone, but everyone has some choice. (Location 836)

think about the possibilities. What might your life be like? What kind of person might you become? (Location 838)

WE HUMANS ARE a social species. We live in groups. We take care of one another. (Location 841)

Part of being a social species, it turns out, is that we regulate one another’s body budgets (Location 843)

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. (Location 846)

When you’re with someone you care about, your breathing can synchronize, as can the beating of your hearts, (Location 857)

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. (Location 867)

When people work in an environment where they can learn to trust one another, they’ll have less burden on their body budgets, saving resources that can be invested in new ideas. (Location 873)

Alfred, Lord Tennyson, famously wrote, “ ’ Tis better to have loved and lost than never to have loved at all.” (Location 878)

a breakup might make you feel like you’re dying, but constant loneliness is likely to hasten your death. (Location 879)

solitary confinement in jail ​— ​ enforced loneliness ​— ​ is like capital punishment in slow motion. (Location 880)

when people are less familiar to you, it can be harder to empathize. You might have to learn more about the person, an extra effort that translates into more withdrawals from your body budget, which can feel unpleasant. (Location 884)

research shows that we all can tweak one another’s nervous systems quickly with mere words in very physical ways (Location 900)

many brain regions that process language also control the insides of your body, including major organs and systems that support your body budget. (Location 910)

If you constantly struggle in a simmering sea of stress, and your body budget accrues an ever-deepening deficit, that’s called chronic stress, (Location 922)

Over time, anything that contributes to chronic stress can gradually eat away at your brain and cause illness in your body. This includes physical abuse, verbal aggression, social rejection, severe neglect, and the countless other (Location 924)

the human brain doesn’t seem to distinguish between different sources of chronic stress. (Location 926)

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. (Location 940)

if you eat healthful, saturated fats, such as those found in nuts, within one day of being stressed, your body metabolizes these foods as if they were filled with bad fats. (Location 942)

You have to live with your own conscience there. (Location 943)

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. (Location 945)

history is filled with examples of overcoming our biology so we can live our values. (Location 961)

freedom always comes with responsibility. We are free to speak and act, but we are not free from the consequences of what we say and do. (Location 967)

Creativity and innovation often mean failing repeatedly and having the tenacity to pick yourself up and try again. This extra effort takes extra energy. (Location 974)

we influence the brains and bodies of those around us with our actions and words, and they return the favor. (Location 993)

Human brains make many different kinds of minds. (Location 1001)

people who grow up in Balinese culture, as well as in the Ilongot culture in the Philippines, do not experience what we Westerners call cognition and emotion as different kinds of events. They experience what we would call a blend of thinking and feeling, but to them it’s a single thing. (Location 1003)

in some other cultures, attempts to peer into another person’s mind are considered unnecessary. The Himba people of Namibia often figure each other out by observing each other’s behavior, not by inferring a mental life behind that behavior. (Location 1008)

Thunberg’s mind is on the autism spectrum, and she says things that others aren’t willing to say. She calls her condition a “superpower” that helps her continue her mission when people criticize her efforts. (Location 1014)

A mind is something that emerges from a transaction between your brain and your body while they are surrounded by other brains-in-bodies that are immersed in a physical world and constructing a social world. (Location 1023)

It’s important for humans to have many kinds of minds, because variation is critical for the survival of a species. (Location 1030)

the MBTI’s scientific validity is pretty dubious. This test and its many cousins typically work by asking what you believe about yourself, which research suggests may have little to do with your actual behavior in daily life. (Location 1045)

“normal” is relative. (Location 1048)

Brains have a lot of common features; minds, less so, because minds depend in part on micro-wiring that is tuned and pruned by culture. (Location 1057)

in some Eastern cultures, such as those that practice Buddhism, mind and body are much more integrated. (Location 1060)

As far as I can tell, the human mind has no universal defining features. (Location 1061)

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. (Location 1069)

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. (Location 1072)

Your brain summarizes what’s going on with your body in the moment, and you feel that summary as affect. (Location 1081)

Unfortunately, affect is not so precise. It just tells you, Beep! You feel like crap. Then your brain must predict what to do next to keep you alive and well. (Location 1086)

Scientists are still puzzling out how your brain’s body-budgeting activities, which are physical, become transformed into affect, which is mental. (Location 1088)

You can modify your mind. (Location 1095)

Partygoers drink alcohol to create minds that are more relaxed and less inhibited in social situations (and miraculously, other people around them suddenly become much more attractive). (Location 1096)

movies like Lost in Translation (Location 1100)

You change cultures when you switch between work life and home life, and when you change jobs (Location 1110)

No kind of mind is inherently better or worse than any other. Some variations are just more tailored to their environment. (Location 1115)

We all live in a world of social reality that exists only inside our human brains. (Location 1127)

Social reality means that we impose new functions on physical things, collectively. (Location 1131)

The boundary between social reality and physical reality is porous, (Location 1136)

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. (Location 1141)

for social reality to spread and persist, language is usually more efficient than other symbols. (Location 1152)

In your cerebral cortex, compression begins with small neurons that carry sense data from your eyes, ears, and other sense organs. Some of this data may already have been predicted by your brain, and some is new. The new sense data is passed by the small neurons to larger, better-connected neurons, which compress the data into summaries. (Location 1176)

The process continues all the way to the densely wired front of your brain, where the very largest, most connected neurons create the most general, most compressed summaries of all. (Location 1179)

The psychological meaning of abstraction, though, has a different focus. It’s not about the details of paintings and symbols; it’s about our ability to perceive meaning in them. (Location 1188)

Compression enables sensory integration. Sensory integration enables abstraction. (Location 1206)

Each of the Five Cs is found in other animals to varying extents. (Location 1209)

Rats teach one another what’s safe to eat by marking palatable foods with an odor. (Location 1215)

as far as we know, humans are the only animal whose brains have enough capacity for compression and abstraction to create social reality. (Location 1218)

Most animals have evolutionary adaptations that make them specialists in their niches, like an elk’s antlers or an anteater’s tongue. But humans became generalists; (Location 1225)

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. (Location 1229)

Lynda Barry writes, “We don’t create a fantasy world to escape reality. We create it to be able to stay.” (Location 1231)

we often don’t realize that we make it. The human brain misunderstands itself and mistakes social reality for physical reality, which can cause all sorts of problems. (Location 1238)

You uphold social reality by your everyday behaviors. (Location 1247)

We could have a leader who says terrible things, all captured on video, and then news outlets could agree that the words were never said. That’s what happens in a totalitarian society. (Location 1255)

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. (Location 1259)

We have more control over reality than we might think. We also have more responsibility for reality than we might realize. (Location 1260)

across the expanse of evolutionary time ​— ​ with the innovation that comes from trial and error and the deaths of trillions of animals ​— ​ you ended up with a human brain. (Location 1268)

A brain that’s so complex that we describe it by metaphors and mistake them for knowledge (Location 1271)

A brain that’s so skilled at rewiring itself that we think we’re born with all sorts of things that we actually learn (Location 1272)

A brain that’s so effective at hallucinating that we believe we see the world objectively, and so fast at predicting that we mistake our movements for reactions (Location 1273)

This book also wouldn’t exist were it not for the boundless enthusiasm and expert guidance from my editor at Houghton Mifflin Harcourt, Alex Littlefield. I’m particularly grateful for his careful reading and his encouragement to combine complicated observations about the brain with big ideas of what it means to be a human being. (Location 1303)

This book was made possible with a fellowship from the John Simon Guggenheim Foundation and a book grant from the Alfred P. Sloan Foundation. (Location 1327)

At its most anterior tip, an amphioxus has a small group of cells on one side, called an eyespot. These cells are photosensitive and can detect gross changes in light and dark, so if a shadow falls on the animal, the animal moves away. (Location 1354)

Across the Bridge: Understanding the Origin of the Vertebrates, (Location 1376)

Brains Through Time: A Natural History of Vertebrates (Location 1377)

Scientists believe that our common ancestor with amphioxi resembled modern amphioxi very closely, because amphioxi’s environment (their niche) has barely changed in the past 550 million years, so they wouldn’t have had to adapt much. (Location 1379)

7half.info/ancestor (Location 1389)

a statement that something is a process that embodies a goal with no ultimate end point. In stating that the brain is not for thinking but for regulating a body in a particular niche, I am not implying that body budgeting ​— ​ allostasis ​— ​ has some final end state. (Location 1396)

The organs inside your body, such as your heart, stomach, and lungs, are called viscera, and they are part of broader visceral systems below your neck, such as your cardiovascular system, your gastrointestinal system, and your respiratory system, respectively. Movements that happen inside your heart, gut, lungs, and other organs are called visceromotor movements. (Location 1418)

Some visceral organs, like your lungs, require your brain in order to function. Your heart and your gut, however, have their own intrinsic rhythms, and the visceromotor system in your brain fine-tunes them. (Location 1423)

In a larger body, the inside of the body is farther away from the outside world, so new systems have evolved, like one that pumps water over gills to facilitate gas exchange, and the kidneys and an extended gut to excrete waste. (Location 1438)

In the real world, facts have some probability of being true or false in a particular context. (Location 1463)

The Accidental Species: Misunderstandings of Human Evolution, (Location 1464)

Biology as Ideology: The Doctrine of DNA (Location 1469)

Mistakes are part of the normal process of science, and when scientists acknowledge them, they are great opportunities for discovery. (Location 1469)

Stuart Firestein’s books Failure: Why Science Is So Successful and Ignorance: How It Drives Science (Location 1470)

Georg Striedter’s Principles of Brain Evolution and Striedter and Northcutt’s Brains Through Time (Location 1477)

the difference between the primary somatosensory cortex in rats and humans. The rat’s single region is like a single pot containing all the ingredients, and the four human regions are like four pots with separate ingredients. (Location 1488)

Two animals can have the same genes, but those genes can function differently or produce different structures. And even within the same animal, a network of genes can perform different genetic activities at different times in development. (Location 1494)

Henry Gee’s book Across the Bridge.) (Location 1496)

How Emotions Are Made: The Secret Life of the Brain (Location 1518)

In general, scientists estimate the number of neurons in a brain using stereological methods, which employ probability and statistics to estimate the three-dimensional structure of neurons from two-dimensional images of brain tissue. (Location 1544)

If you place an obstacle in front of a person with damage to the primary visual cortex, the person won’t consciously see the obstacle but will walk around it. This phenomenon is called blindsight. (Location 1570)

The Blank Slate by psychologist Steven Pinker; (Location 1582)

Hebb’s book The Organization of Behavior: A Neuropsychological Theory (Location 1607)

The Philosophical Baby: What Children’s Minds Tell Us About Truth, Love, and the Meaning of Life (Location 1611)

Besides sharing attention, other abilities are probably important to developing a spotlight of attention. One is the brain’s control of the head, an ability that develops over the first few months of life. Another is control of the muscles of the eye, called oculomotor control, which improves during the first few months of life. (Location 1612)

The cost of lifting children out of poverty, the report states, is far less than the price paid for the consequences of poverty after the children grow up. (Location 1621)

psychologist Isaiah Pickens points out the irony that in our culture, we start to treat people as more responsible for their actions right around the time that the ill effects of poverty and adversity manifest themselves in more serious ways. (Location 1622)

2018 TEDx Talk “Cultivating Wisdom: The Power of Mood,” (Location 1627)

Sense data is not only ambiguous but also incomplete. Information about the world and the body is lost when it’s processed by your retina, cochlea, and other sensory organs and sent to the brain. (Location 1629)

immunologist and neuroscientist Gerald Edelman’s proposal that your ongoing conscious experience is the “remembered present.” (Location 1634)

Surfing Uncertainty: Prediction, Action, and the Embodied Mind (Location 1647)

TED Talk “Your Brain Hallucinates Your Conscious Reality.” (Location 1648)

2018 TED Talk “You Aren’t at the Mercy of Your Emotions ​— ​ Your Brain Creates Them,” (Location 1651)

Studies show that chronic stress eats away at the brain and the body over the long term regardless of whether the stress stems from ongoing physical abuse, sexual abuse, or verbal aggression. (Location 1668)

chronic stress causes brain atrophy. (Location 1672)

we can’t view the microarchitecture of a living human brain in enough detail to know exactly what changes occur. This is why scientists study the impact of stress on nonhuman animals and then carefully generalize to humans where possible. (Location 1676)

swimming in a sea of sustained aggression places adolescents on a developmental trajectory that can lead to physical and mental illness. (Location 1690)

For a primer, see Mayr’s book What Makes Biology Unique, and for a more thorough treatment, see his book Toward a New Philosophy of Biology. (Location 1727)

The MBTI and various other personality tests have no more scientific validity than horoscopes. (Location 1730)

You can’t measure behavior by asking people their opinions about their behavior. You have to observe that behavior in multiple contexts. (Location 1734)

Darwin’s Unfinished Symphony: How Culture Made the Human Mind (Location 1755)

The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter (Location 1759)

biologist Richard Wrangham’s book Catching Fire: How Cooking Made Us Human (Location 1767)

The cells that convert chemicals in the air into neural signals are located in a structure called the olfactory bulb. These cells send information directly to the cerebral cortex, bypassing the thalamus. (Location 1779)

Presumably, a brain can achieve abstraction by other means than compression, because other animals without huge brains (such as dogs) or without a cerebral cortex (such as bees) can treat two things as similar based on their function ​— ​ that is, they can do abstraction to some extent. (Location 1789)

The extended evolutionary synthesis, which considers evolutionary and developmental (“evo-devo”) neuroscience, proposes other means of transfer, such as epigenetics and niche construction, as well as cultural evolution and gene-culture co-evolution. (Location 1799)

“We don’t create a fantasy world to escape reality. We create it to be able to stay”: This quote about fantasy worlds by author and cartoonist Lynda Barry comes from her book What It Is. See 7half.info/barry (Location 1808)

Lighter skin tones are better adapted for environments with less ultraviolet (UV) light. Lighter pigmentation allows the skin to absorb more light and produce more more vitamin D, which is important for bone growth, bone strength, and a healthy immune system. (Location 1812)

darker skin tones are better adapted for environments with more UV light, because darker pigmentation prevents the skin from absorbing too much light. This in turn slows the destruction of vitamin B9, folic acid, which is important for cell growth and metabolism and is particularly important in early pregnancy (since sunlight breaks down folate). (Location 1814)

Living Color: The Biological and Social Meaning of Skin Color (Location 1818)