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7½ Lessons for the Brain, Barrett (2020)

Study notes for this short, pithy book about the brain, our relationship with it, and the nature of reality.


½ Your Brain is Not for Thinking

Your brain’s most important job is not thinking; it is to control your body – to manage allostasis – ie. predicting and preparing to meet the body’s energy needs (prediction beats reaction in nature) before they arise, so you can efficiently make worthwhile movements and survive. Your brain is the command center that supervises, regulates, and protects the systems and subsystems that comprise your entire body.

1. You Have One Brain (not Three)

Paul MacLean’s three-layered brain – neocortex (rational), limbic (emotional), lizard (survival) – is a modern myth that persists in popular culture because of its accessibility and our ego; the conflict between the rational and the emotional is based on this belief. However, this is not borne out by science – the rational/emotional dichotomy is a false one – there is only one brain, and its rational behavior consists of making a good body-budgeting investment in a given situation.

2. Your Brain is a Network

A network (a tree-like structure of neurons, synapses, dendrites, axons, etc.) is the best scientific description of a brain today – a physical structure that is capable of reconfiguring itself (often very quickly) to integrate vast amounts of information efficiently. The brain is considered a complex system, able to configure itself into an enormous number of distinct neural patterns. It is capable of degeneracy – almost like redundancy, instead of the same set of neurons being responsible for a certain action, different sets of neurons are capable of this task. Complex brains remember more, are more creative and adaptable, and are also more resilient to injury. Note that other species on Earth also have brains with high complexity.

3. Little Brains Wire Themselves to Their World

The brain of a baby requires physical and social input from its environment (caregivers are particularly critical) to wire itself correctly, a process that nudges it toward higher complexity via tuning – strengthening frequently used or important connections between neurons for future reuse with myelin; and pruning – letting less-used connections weaken and die off, to improve the brain’s metabolic efficiency. The infant brain learns how to regulate its body budget within its environment, learning what is relevant and what can be ignored – its niche.

4. Your Brain Predicts (Almost) Everything You Do

Your brain uses past memories and present sensory input to predictively construct your experience of the world – your physical sensations, what you feel inside your body – in order to plan the best next action. In fact, prediction happens backwards from when you expect – your brain prepares for the action first, and then the predictions are routed to your sensory systems, giving you your sensations. Given that predictions are based on our past experiences, we can choose to accumulate experiences that bias us towards a more desirable set of behaviors.

5. Your Brain Secretly Works with Other Brains

We are a social species, and this also means we regulate one another’s body budgets – we can keep our systems in balance, or stress them through conflict. Language and words have power over our biology. 

6. Brains Make More than One Kind of Mind

Human brains are shaped by culture to make many kinds of minds – eg. a mind that has features called thoughts and emotions (Western), and one that blends them (Balinese); one that attempts to guess another’s state of mind, and another that does not. (Emotions, far from being hardwired at birth, are a construct of culture – How Emotions are Made, also by Lisa Feldman Barrett) This is an evolutionary advantage – ie. variation enables natural selection. Instead of a universal mind, during our long childhood, infant brains become tuned to the variants of environment and culture they are born into, with genetic variation an additional, complementary layer (see The Gardener and the Carpenter by Alison Gopnik). A useful feature of the mind is mood or affect – divided into pleasant/unpleasant, idle/activated axes – constantly generated by the brain to summarize the sense data it receives, whether you notice it or not.

7. Our Brains Can Create Reality

We live in a world of social reality that exists only inside our human brains – our geographic borders, the financial system, etc. – as opposed to the physical reality of the Earth itself, its rocks, trees, oceans, etc. We create this social reality with other people, something uniquely human. Social reality requires creativity – the ability to invent and innovate; communication – sharing ideas efficiently, the primary feature of which is language; copying – passing culture and norms down to newcomers including children, through oral and written means; cooperation – working together is the basis of civilization. Most interesting is the fifth C, compression – the brain’s ability to compress signals from sparsely connected neurons into summaries held within densely connected neurons, giving rise to our ability to think abstractly, assigning multiple meanings and functions to a single object, and thinking in ideas. Some animals are also capable of compression, but while a chimpanzee can use a stick as a tool, it cannot construct social reality with it – ie. assign a non-physical function to it, so that holding it represents tribal dominion.