Seven and a Half Lessons About the Brain – Lisa Feldman Barrett

Thoughts: Neat book! Not very long, easy to understand and with apt metaphors, but with some counterintuitive conclusions (which, as Barrett pitches it, seem to reflect growing consensus among neuroscientists).

(The notes below are not a summary of the book, but rather raw notes - whatever I thought, at the time, might be worth remembering. I read this as an e-book, so page numbers are as they appeared in the app I used, Libby.)

Barrett, Lisa Feldman. 2021. Seven and a Half Lessons About the Brain. Mariner Books.

The Half Lesson: Your Brain Is Not for Thinking

• 14: “Your brain’s most important job is to control your body—to manage allostasis—by predicting energy needs before they arise so you can effectively make worthwhile movements and survive.” - i.e. your brain allows your body to make informed investments of resources in order to gain more resources
  • 12: Allostasis: body budgeting, i.e. making sure your body has all the resources it needs—water, salts, carbohydrates, etc.—and that they’re allocated appropriately
• 15: “You and I do not experience or 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.”

Lesson No. 1: You Have One Brain (Not Three)

• summary: the idea that humans have three brain layers—lizard, mammal and neocortex—and that they act in opposition to each other (e.g. the neocortex as the seat of rational thought struggling against the instinctive/impulsive cortex and subconscious limbic system) doesn’t hold up.
• 27: “Rational behavior… means making a good body-budgeting investment in a given situation” - this definition describes a low-level/biological instrumental rationality

Lesson No. 2: Your Brain Is a Network

• 29: mentions Kahneman’s system 1 and system 2 processing. These systems are often misunderstood as structures in the brain, but Kahneman is “very clear that Systems 1 and 1 are metaphors about the mind” - i.e. a useful, high-level abstraction, not a physical reality
• 35: the brain has a whole bunch of overlapping networks, and individual neurons can participate in multiple different networks. When a scientist names a brain area after some function, it means that that network responsible for that function is localized in that area, but it’s almost always the case that other networks overlap with that brain area
• 36: degeneracy: redundancy within a system. e.g. multiple different genotypes can code for the same phenotype, and multiple collections of neurons can accomplish the same task. “Even a simple… action… when done more than once, can be guided by different sets of neurons. This phenomenon is called degeneracy”
• 37: complexity in the brain: “a system has higher or lower complexity depending on how much information it can manage by reconfiguring itself” - the complexity of how neurons communicate with each other allows a great deal of flexibility and learning
  • complexity depends to some extent on degeneracy - even if one highly-connected neuron were to die, degeneracy gives the entire brain system resilience, allowing it to rewire and adapt to the change in structure without completely falling apart

Lesson No. 3: Little Brains Wire Themselves to Their World

• 50-51: Barrett suggests that, when developing, infant brains need a balance of hands-on care and hands-off time - the hands-off time allows the brain to learn to do its own body budgeting, rather than having the caretaker do all the budgeting for it.
  • 51: “Persistent neglect, over a long time with no relief, is almost always harmful to a little brain. The scientific evidence is clear on this point. You can’t just feed and water babies and expect their brains to grow normally. You must also meet their social needs with eye contact and language and touch. If these needs go unmet, the seeds of illness may be planted very, very early.”
  • 51: “We see similar consequences when little brains develop in poverty. Research shows that early and long exposure to poverty is bad for the developing brain.”

Lesson No. 4: Your Brain Predicts (Almost) Everything You Do

• opens with an anecdote about a man, raised as a child soldier, coming across guerilla fighters in the jungle: a line of soldiers led by a man carrying an AK-47. It was only after his companion said “don’t shoot, it’s just a boy” that he saw what was actually there: a boy, holding a stick, leading a line of cows.
• 58: “Your brain actively constructs your experiences.” Since so much information is flowing in from your senses at all times, your brain constructs your experiences based on similar situations you’ve previously experienced.
• 59: “In much the same way, your brain also construct what you feel inside your body.” Yes, you’re receiving signals from sensing neurons in your body, but your brain has to interpret this clamor of hundreds of signals, and it predicts/fills in your internal sensations based on experiences/situations you’ve experienced before.
• 60: the brain processes the world predictively: e.g. if you are thirsty and drink a cup of water, you stop feeling thirsty almost immediately, yet the water takes 20 minutes to reach your bloodstream. Much of what is going on in your brain all the time is networks of neurons working to predict the external signals that network will next receive
• 62: “So, your brain issues predictions and check 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.”
• 63: “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.”
• 64: your perceptions and behaviors now are shaped by all your experiences in the past - with different experiences, you would perceive the world differently than you do now.
  • “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 create new experiences. You can try new activities. Everything you learn today seeds your brain to predict differently tomorrow.”

Lesson No. 5: Your Brain Secretly Works with Other Brains

• 68-69: every interaction you have with another person shapes how your brain predicts and perceives, and thus how it regulates your body budget. Body-budgeting based on social interactions is called co-regulation.
  • 69: “This co-regulation has measurable effects. Changes in one persons body often prompt changes in another persons body, whether the two are romantically involved, just friends, or strangers meeting for the first time.”
  • conversely, it’s worth remembering that your actions affect others’ body budgets

Lesson No. 6: Brains Make More than One Kind of Mind

• 83: “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.”
  • “As far as I can tell, the human mind has no universal defining features. Pick any mental feature that’s unique to humans, such as rich, spoken language, and you can always find some humans who don’t have it, such as newborn infants. Alternatively, pick any mental features that virtually all humans have, such as cooperation, and you can find plenty of other animals that have it too.”
• 84: “And especially useful feature of the mind, and one of the closest things we have to universal mental feature, is mood—the general sense feeling that comes from your body. Scientists call it affect”
  • affect varies along two dimensions: pleasant-unpleasant, and activated-idle
  • affect isn’t emotion: “Your brain produces affect all the time, whether you’re emotional or not and whether you notice it or not”
  • 85: a person’s affect reflects the current state of their body budget

Lesson No. 7: Our Brains Can Create Reality

• 89: human brains create social reality - things that aren’t physically there (e.g. credit, or borders) that exist because people agree or behave as though they exist
  • as a nod to postmodernists, social reality is one kind of reality for which different people actually have different realities. Think of people who differ in where they think the border between Israel and Palestine is, or whether they think or Tibet is a country or not.
• 89: as far as we know, no non-human animal creates social realities. Barrett outlines five necessary mental ingredients—the “Five C’s”—that are necessary for creating social reality: creativity, communication, copying, cooperation, compression
  • 91: compression: taking a bunch of data, and boiling it down into a summary that can be communicated on more efficiently
    • Barrett states that the brain does this multiple times during perception - small neurons connected to sense organs pass signals on to larger, more-connected neurons, which pass them on to even larger more highly connected neurons, summarizing and compressing at each step until the cerebral cortex receives big-picture summaries such as “it’s a cookie” or “it’s a table”, rather than readouts from all the individual neurons in the eye
    • 92: Barrett states that this process travels from back-to-front in the brain - does it literally go back-to-front, or is this just a metaphor?
• 94: each of the Five C’s can be found in other animals, but it seems that it’s only in humans that all coincide and thus reinforce each other
• 97: “Social reality does have its limits; after all, it’s constrained by physical reality. We could all agree that flapping our arms will let us soar into the air, but that won’t make it happen. Even so, social reality is more malleable than you might think. People can agree that dinosaurs never existed, ignore all evidence to the contrary, and build a museum about a dinosaur-free past. 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. Social reality may be one of our greatest achievements but it’s also a weapon we can wield against each other. It is also vulnerable to being manipulated. Democracy itself is social reality.”