The Brain: The Story of You

by David Eagleman

Given the brain’s centrality to our lives, I used to wonder why our society so rarely talks about it, preferring instead to fill our airwaves with celebrity gossip and reality shows. But I now think this lack of attention to the brain can be taken not as a shortcoming, but as a clue: we’re so trapped inside our reality that it is inordinately difficult to realize we’re trapped inside anything.

is born remarkably unfinished. Instead of arriving with everything wired up – let’s call it “hardwired” – a human brain allows itself to be shaped by the details of life experience. This leads to long periods of helplessness as the young brain slowly molds to its environment. It’s “livewired”.

As many as two million new connections, or synapses, are formed every second in an infant’s brain.

In a sense, the process of becoming who you are is defined by carving back the possibilities that were already present. You become who you are not because of what grows in your brain, but because of what is removed.

A mature pleasure-seeking system coupled with an immature orbitofrontal cortex means that teens are not only emotionally hypersensitive, but also less able to control their emotions than adults.

who we are as a teenager is not simply the result of a choice or an attitude; it is the product of a period of intense and inevitable neural change.

On the flip side, they found that negative psychological factors like loneliness, anxiety, depression, and proneness to psychological distress were related to more rapid cognitive decline. Positive traits like conscientiousness, purpose in life, and keeping busy were protective.

The more we keep our brains cognitively fit – typically by challenging them with difficult and novel tasks, including social interaction – the more the neural networks build new roadways to get from A to B.

Consciousness emerges when neurons are coordinating with one another in complex, subtle, mostly independent rhythms. In slow-wave sleep, neurons are more synchronized with one another, and consciousness is absent.

who you are depends on what your neurons are up to, moment by moment.

You don’t perceive objects as they are. You perceive them as you are.

Your interpretation of physical objects has everything to do with the historical trajectory of your brain – and little to do with the objects themselves.

Visual data goes through more complex processing than auditory data.

In fact, the brain generates its own reality, even before it receives information coming in from the eyes and the other senses. This is known as the internal model.

what gets sent back to the visual cortex is what fell short in the expectation (also known as the “error”): the part that wasn’t predicted away.

his senses were providing his brain with no new input, so his internal model was able to run free, and he experienced vivid sights and sounds. Even when brains are unanchored from external data, they continue to generate their own imagery. Remove the world and the show still goes on.

Instead of using your senses to constantly rebuild your reality from scratch every moment, you’re comparing sensory information with a model that the brain has already constructed: updating it, refining it, correcting it. Your brain is so expert at this task that you’re normally unaware of it. But sometimes, under certain conditions, you can see the process at work.

your internal model operates under the assumption that the world outside is stable. Your eyes are not like video cameras – they simply venture out to find more details to feed into the internal model. They’re not like camera lenses that you’re seeing through; they’re gathering bits of data to feed the world inside your skull.

Twenty percent of the calories we consume are used to power the brain. So brains try to operate in the most energy-efficient way possible, and that means processing only the minimum amount of information from our senses that we need to navigate the world.

Color is an interpretation of wavelengths, one that only exists internally.

The real world is not full of rich sensory events; instead, our brains light up the world with their own sensuality.

Synesthesia is the result of cross-talk between sensory areas of the brain, like neighboring districts with porous borders. Synesthesia shows us that even microscopic changes in brain wiring can lead to different realities.

signals. A slightly different pattern, and one can suddenly be trapped inside a reality in which strange and impossible things unfold.

Our time distortion is something that happens in retrospect, a trick of the memory that writes the story of our reality.

Once etched into the circuitry of the brain these skills can be run without thinking – without conscious effort – and this frees up resources, allowing the conscious me to attend to, and absorb, other tasks.

Some of this reconfiguring is guided by reward systems, which globally broadcast a neurotransmitter called dopamine when something has gone well.

There’s an interesting upshot to automatized skills: attempts to consciously interfere with them typically worsen their performance. Learned proficiencies – even very complex ones – are best left to their own devices.

This is your brain on flow.

During flow, the brain enters a state of hypofrontality, meaning that parts of the prefrontal cortex temporarily become less active.

The reach of the unconscious mind extends beyond control of our bodies.

Placing fruit at eye level in supermarkets nudges people to make healthier food choices. Pasting a picture of a housefly in urinals at airports nudges men to aim better.

Consciousness gets involved when the unexpected happens, when we need to work out what to do next.

Even when decisions seem spontaneous, they don’t exist in isolation.

The conscious mind excels at telling itself the narrative of being in control.

This picture can be seen in one of two ways (this is known as perceptual bi-stability): the lines on the page are consistent with two very different interpretations.

Unlike computers, the brain runs on conflict between different possibilities, all of which try to out-compete the others.

It’s all you – but it’s different parts of you.

The world would not be better if we all behaved like robots.

The key to effective learning lies in tracking this prediction error: the difference between the expected outcome of a choice and the outcome that actually occurred.

options right in front of us tend to be valued higher than those we merely simulate. The thing that trips up good decision making about the future is the present.

To the brain, the future can only ever be a pale shadow of the now.

people structure things in the present so that their future selves can’t misbehave. By lashing ourselves to the mast we can get around the seduction of the now. It’s the trick that lets us behave in better alignment with the kind of person we would like to be. The key to the Ulysses contract is recognizing that we are different people in different contexts. To make better decisions, it’s important not only to know yourself but all of your selves.

Knowing yourself is only part of the battle – you also have to know that the outcome of your battles will not be the same every time.

decisions get reprioritized as other needs rise in importance. Valuations change as circumstances change.

“ego-depletion,”

self-control requires energy, which means we have less energy available for the next thing we need to do. And that’s why resisting temptation, making hard decisions, or taking initiative all seem to draw from the same well of energy. So willpower isn’t something that we just exercise – it’s something we deplete.

We are deeply social creatures.

Without meaning to, people ape one another.

couples who are married for a long time begin to resemble each other, and the longer they’ve been married, the stronger the effect.

This network is summarized as the pain matrix.