PDF Summary:Seven and a Half Lessons About the Brain, by Lisa Feldman Barrett

In Seven and a Half Lessons About the Brain, neuroscientist Lisa Feldman Barrett sheds light on the inner workings of the brain and how they impact feelings, behaviors, and relationships. While providing an entertaining peek behind the curtain, she argues that by understanding the basics of how your brain works, you can take a more active role in deciding how to think and behave.

Barrett’s book is a collection of eight informal essays—one for each lesson. Our guide explores those lessons through four themes: how the brain is organized, how the brain operates, how the brain develops, and how brains collaborate. Along the way, we compare Barrett’s explanations of the brain to those of other experts in neurology and offer practical applications for the insights she shares.

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The Brain’s Most Important Function

While Barrett argues that the brain’s single most important job is managing the body’s energy budget, in The Body Keeps the Score, Bessel van der Kolk breaks down the brain’s primary role into several tasks, including:

• Signaling when your body needs essentials such as food, water, rest, shelter, safety, and sex

• Interpreting the world around you to point you in the right direction to find and satisfy those essential needs

• Creating the energy and initiating the actions to achieve those tasks

• Warning you of dangers and opportunities you may encounter as you pursue those tasks

• Adapting and responding to changing circumstances along the way

Half Lesson: How Brains Evolved From Cells

To better understand how allostasis (the brain’s process of energy budgeting) works, it helps to know how it has affected our brain’s evolution. Primitive organisms evolved to require more energy, so their energy-budgeting cells had to evolve to keep up with their needs.

Barrett explains that, before brains existed, primitive creatures had energy-budgeting cells that kept track of their energy needs. These cells signaled to the rest of the body when it needed to eat (or move to find food), or rest—whichever would preserve its energy best in that moment.

During the Cambrian period (starting about 541 million years ago and lasting for about 56 million years), primitive animals started needing more energy and the process of budgeting energy became more complex, so those energy budgeting cells clustered together to form a brain. Barrett explains that this evolution was due to two main factors that made energy budgeting more challenging:

1. Some primitive creatures began hunting, which meant they now had to hunt for food and escape predators. They began developing more sophisticated senses to detect danger and opportunity and to make decisions that directly impacted their energy budgets, such as whether to move (and expend energy) to try and catch prey (to gain energy) or escape danger.

(Shortform note: Hunting continued to impact our brains well after the Cambrian period. Around 2.6 million years ago, as the populations of large animals dwindled, early humans needed to exercise more skill to catch smaller and more agile prey. (Think about the difference it would make to catch a large and conspicuous mammoth versus a quick-moving hare with primitive tools.) Scientists believe that this change demanded more of human brains, which triggered a period of growth where brains got much larger—possibly to accommodate those new skills.)

2. Primitive creatures began evolving into more complex organisms with more organs and internal systems. The more complex an organism is, the more complex its energy budgeting becomes because each organ and system has specific energy requirements that need to be satisfied.

(Shortform note: In Your Inner Fish, Neil Shubin sheds light on one of the reasons complex organisms have higher energy requirements. Early Precambrian creatures were made of the same type of “glue” (collagen and proteoglycan) that allows human body cells to stick together to build materials and organs. However, more evolved organisms require this glue to be a mix of molecules that differs depending on the organ it’s forming—for instance, a bone versus an eye. Without the molecule mix attaching cells to each other, bodies couldn’t be formed. This requires more energy in order to create the right “glue” and assign it to the right body part or system.)

Lesson: Allostasis Impacts Your Sensory Experience

Barrett says that your own sophisticated sensations and movements are also the result of your brain performing allostasis. Your sensory experience is actually a combination of external data from your environment and internal data from inside your body. Your brain then combines this information with memories of similar situations to motivate you to make a change that helps manage the body’s energy budget.

For example, your brain senses heat from the sun on your skin (an external sensation) and a rise in your body temperature (an internal sensation), and it tells your body to produce sweat to regulate your temperature. Your brain has to make millions of reactions like these all day, and it has to do them efficiently to stay alive. If you spend too much time in the sun without drinking water and cooling your skin with sweat, you could die. So, Barrett argues, the pressure is on for your brain to make the right call quickly.

Barrett explains that this is where the third source of information comes into play: the brain’s memories of what you’ve done before when you encountered similar information. Before it fully processes the external and internal information it receives, it searches its memory for previous situations where the environment and your body felt similarly. It recalls what it did in that situation and triggers an action for today. This allows your brain to be one step ahead and make decisions quickly and efficiently.

All of this happens before the brain has time to contrast the real sensory data with the experience it created for you. Barrett says this is why you feel less thirsty immediately after drinking water, even though that water won’t reach your bloodstream until 20 minutes later. Your brain knows you’ll be satisfied in a little while, so it creates the experience of quenched thirst.

Help Your Brain Create More Manageable Sensations

Understanding how the brain creates your experiences can help you manage sensations better, especially challenging ones. We tend to think that when we hurt ourselves, like when you stub your toe, a message travels from your toe to the brain alerting it of the pain. However, it’s actually your brain noticing that you stubbed your toe and creating pain to alert you to what happened so you can ice it or avoid walking on it.

You can leverage this mechanism by “teaching” your brain what sensations to expect and whether to be concerned by them or not. For example, pregnant women who are preparing for labor are often taught to refer to pain during labor as intensity and contractions as surges so they can visualize the sensation in a less negative and more manageable way.

The Brain Can Make Mistakes—and Learn

Barrett says that, sometimes, the experience your brain constructs turns out to be inaccurate, so you perceive something different from reality. For example, let’s say your brain senses that the sun is down (an external sensation) and your energy is low (an internal sensation). When it compares that data to the historical data in its memory, it comes to the conclusion that you need to eat, so it signals your body to search for food. But the reality might be that you’re tired, not hungry.

However, the brain has the chance to realize it jumped to the incorrect conclusion by contrasting the experience it created with the sensory data. Barrett says that this is what we call learning: The brain makes a mistake, realizes it, and adjusts its database of historical data so it can make a better decision the next time it encounters similar information. By making an intentional effort to learn, you can help your brain make better decisions in the future. For example, if you notice that you eat a snack every day right before bedtime, it might be a good idea to check whether you’re actually just tired. Instead of reaching for food, you might need to just go to bed.

How to Teach Your Brain

It’s easy to become trapped in the decisions your brain makes automatically. To avoid getting trapped in incorrect patterns of behavior and help your brain learn, there are two strategies you can deploy: reflection and visualization.

Reflection: Observe your actions and decisions as impartially as possible. Ask yourself why you reacted the way you did and whether you skipped over important information that might have been useful. For example, imagine that you regularly get upset with a coworker but aren’t sure why. By reflecting, you might notice that the coworker reminds you of someone else, and that memory is triggering your negative reactions rather than what the coworker does.

Visualization: When you notice a pattern you want to change, use visualization to train your brain to follow a different pattern. For example, through visualization, you can walk your brain through different situations with that coworker where, instead of getting upset, you remind yourself of why you’re feeling triggered and pause before reacting. Then, when you face the coworker again, your brain will be trained to react in a different way.

Part 3: How the Brain Develops

So far we've explored the brain's hardware—its neurons, networks, and functions—but each individual's brain develops differently, based on a combination of their genes and their environment. According to Barrett, brain development depends on the interaction between the genetic information already present in the brain and the environment it develops in, and this interaction has great implications for the healthy development of children’s brains.

Lesson: The Brain Needs Lots of Help to Develop Successfully

Barrett explains that after birth, a baby’s brain develops according to its genetic coding and the physical and social environment. Genes help develop the basic infrastructure of the brain while environmental input triggers brain plasticity to develop certain neural connections more or less strongly.

Barrett identifies two specific processes that take place in the newborn’s brain as genes and the environment interact:

• Tuning: Important connections between neurons get stronger the more they’re used or the more essential they are for energy budgeting. For example, the baby learns to suck on a bottle or her mother’s breast very quickly because it’s a crucial energy budgeting task that she repeats several times a day. (Shortform note: Babies are born with roughly 100 billion neurons, and during their first year of life, babies’ brains generate more than a million new neural connections each second.)
• Pruning: Unnecessary connections are dismantled to make room for more important ones. For example, babies are born with connections to help them identify a wider variety of flavors than adults, but over time most of those connections are lost to prioritize the ones that help them distinguish flavors they’re more commonly exposed to. (Shortform note: This process of synaptic pruning happens when a child is about six years old.)

(Shortform note: Compared to other animals, a human baby’s brain is woefully unprepared for the world—for example, while other animals can almost immediately start walking, the human brain remains fetus-like for at least two years. Babies are born with immature brains because a full-grown human brain would not make it through the birth canal. As a result, babies rely on their environment to help complete their development. Scientists argue that this fosters human intelligence because human adults need to care for the survival of helpless members of their families, which makes their own brains develop uniquely human skills of survival.)

According to Barrett, the environment—especially the quality of the baby’s caregivers—is essential during this process. While the baby’s brain is developing, caregivers perform energy budgeting tasks for them, such as feeding them, helping them sleep, and comforting them when they’re distressed. This allows the brain to spend more energy tuning and pruning. Conversely, children who don’t receive adequate physical and social support from their environment have difficulties developing their brains. This happens in situations where there is poverty or neglect, for example.

Crucial Tasks of a Caregiver

It might be overwhelming for parents or caregivers to consider the responsibility they have in shaping a child’s brain. But child development specialists suggest focusing on three key tasks (after meeting the child’s needs for food, sleep, and comfort):

• Encourage the child’s innate curiosity by paying attention to what catches their interest and helping them explore and learn about the world.

• Understanding the stages of development a child will go through to give them the kind of stimulus they will benefit from at each stage.

• Helping the child learn to manage anxiety and stress—both of which place a heavy load on their energy budgets.

Lesson: Brains Develop Into Unique Minds

Although our brains (physical organs) share a basic architecture, each one gets tuned and pruned according to its environment, producing widely different minds (individual patterns of thought and action). This is similar to the way two college students might buy the same laptop with the same basic capabilities (brain), but they each load certain programs onto their laptops (and delete others) based on what they are studying (since their needs and culture will be different). One student might have more money and more expensive software and accessories, while the other might use the free or cheap ones (since their conditions and environment will vary as well). As a result, the two computers will appear very different once you boot them up, just like our minds.

Barrett claims that this capacity for brain variation is the result of our brain’s plasticity and complexity, as neurons and neural clusters change to meet environmental needs. This flexibility makes humans adaptable to different environments, aiding in our evolution and survival as a species. As individuals, it also allows us to alter our minds by exposing ourselves to new stimuli and learning intentionally.

(Shortform note: Evolution might help explain why the same human brain can produce a wide range of different minds. As Barrett says, brain variation helps our species’ survival. In fact, evolutionary biologists argue that each type of personality has distinct evolutionary benefits that allow humans to survive and thrive in specific situations. For example, extroverted minds are often more successful at finding a mate, while introverted minds are often more successful at creating stable families. Minds with neurotic tendencies are especially adept at detecting dangers, while agreeable minds are especially adept at picking up on the emotional states of others and creating harmony within a community.)

Part 4: How Brains Collaborate

As we saw in Part 3, the brain requires input from our environment to properly develop. Long after it’s done developing, however, the brain continues to solicit information from other brains to perform daily tasks. This is what makes us social animals, and Barrett claims it has profound effects on our well-being.

Lesson: Brains Collaborate in Four Ways

Barrett explains that our brains are constantly collaborating with each other in four key ways:

1. Our interactions with other people encourage our neurons’ tuning process to strengthen certain neural connections over others. This process is particularly intense when we’re newborns, but it continues throughout life. For example, when you interact often with a person who speaks a different language, you might learn to speak some words in their language to communicate more easily with them.

(Shortform note: Anthropologists found another way that brains collaborate and impact each others’ well-being: They argue that our brain’s reliance on interaction is one reason for long human lifespans. Since young humans are dependent on their environment and the people around them, interacting with them to help them develop gives older humans a reason to stay active and healthy longer.)

2. Our internal bodily functions have a regulating effect on the people around us, Barrett says. Brains coordinate with brains around them, matching breathing and heartbeat patterns, especially when we’re in intense interactions (whether they’re positive or negative). This can have a calming effect, for example, or help you collaborate with others more effectively.

(Shortform note: You don’t even need to be in the same room with someone for your brains to synchronize. A study found that the brains of online gamers playing together from different places can get on the same brain wave frequency. In fact, the more able they are to sync up their brains, the better their performance as a team in the game.)

3. Our conscious actions impact others’ energy budgets and well-being. For example, Barrett claims that saying something comforting to a person in distress can help them relax and require less energy to bring themselves back to a neutral state. On the other hand, acting in a threatening way can trigger their danger response and increase their energy load.

(Shortform note: In How Emotions Are Made, Barrett explains that our influence on others’ emotional states can extend to impact their physical health. For example, if someone is causing you anxiety, your brain can interpret it as a physical danger and generate cortisol to help you be alert. That unnecessary cortisol can trigger inflammation in the body, making you ill and thus turning an anxiety-inducing social encounter into physical illness.)

4. Our brains collaborate to create a shared social reality, which includes all of the sociocultural elements that structure our life and don’t rely on physical reality. For example, we agree on national borders, the value of products and currencies, the authority of certain figures, and the power of laws.

Humans are able to create social reality because we have the following abilities:

• Creativity: the ability to generate new ideas
• Communication: the ability to share those new ideas with others
• Cooperation: the ability to work together to make ideas part of our reality
• Copying: the ability to follow other people’s example
• Compression: the ability to absorb and summarize huge amounts of information and extract meaning from them based on their function rather than their shape.

(Shortform note: Some scientists believe that our capacity to create social reality has made the world more complicated than our brains were prepared for. By using our skills, we’ve made our environment a lot more complex—such as creating government systems, political parties, and elections that millions of people vote in. But our brains are still essentially the same brains that early humans used to live in tribes of around 150 people, and they revert to using the same tools to deal with increasingly complicated problems. For example, we revert to cognitive biases that helped us survive millions of years ago, such as tribalism, but that limit our capacity to handle today’s challenges.)

The Powers and Responsibilities of Brain Collaboration

Barrett claims that the ways our brains collaborate make us a social species, which improves our day-to-day lives. For example, people who have supportive relationships live longer than those who constantly feel lonely. (Shortform note: Other social species, such as some primates and dolphins, also have better health outcomes when their social networks are strong. When they’re isolated or face social stress, however, they suffer from stress, reduced health, and a shorter average lifespan.)

Since we impact each other’s well-being as a social species, Barrett notes that we also have the following responsibilities:

1. We have to make a conscious effort to empathize with people who are different from us. If we don’t make a deliberate effort to do this, our brains default to collaborating and syncing up with people we already understand and agree with.

Empathy is a skill that comes naturally to us, but with limitations, such as who we’re able to empathize with. It’s also a complex skill that needs to be practiced throughout life and that children need to be taught. If you’re a parent or caretaker, you can help your children develop empathy by teaching these skills, which Daniel Siegel and Tina Payne Bryson list in The Whole-Brain Child:

• Seeing another person’s perspective: Help your child practice this skill by frequently asking questions about how someone else might feel and why someone may have reacted in a certain way.

• Interpreting nonverbal communication: Help your child learn to read nonverbal cues by encouraging her to notice other people’s body language, and explaining the emotions it reflects.

• Making amends: Teach your child that there are times when she needs to perform a follow-up action to make things right after a conflict, and help her to determine the appropriate action.

2. We have to find a balance in the conflict between individual rights and the impact we have on each other’s energy-regulating functions. For example, the exercise of individual freedom of speech might have a negative effect on people if our speech causes them stress, which affects the energy-regulating capacity of their brain.

(Shortform note: One way you can keep other people’s actions from having a negative impact on your energy budget and well-being is to make a conscious effort to resolve all conflicts before ending your day. Researchers found that people who worked through arguments on the same day before going to sleep could keep their stress hormone levels from piling up day after day, effectively flushing cortisol out of their system each day to stay healthy.)

3. We have to understand the risks of social reality. Although we generally agree on aspects of social reality like borders and currency, disagreements happen and can be problematic, or even deadly, such as in wars over boundary disputes between nations. Also, some social realities are harmful, such as racism.

(Shortform note: This is perhaps the hardest responsibility to take on because social reality relies on the belief that others experience the world in the same way we do. When we find evidence that others disagree with our social reality or want to change it, we instinctively turn to our families or core social groups that do share our social reality to affirm what we believe. This is why challenging negative social realities is difficult and frequently causes conflict.)