The Brain: The Story of You

by David Eagleman

At birth, a baby’s neurons are disparate and unconnected,

and in the first two years of life they begin connecting up extremely rapidly as they take in sensory information.

As many as two million new connections, or synapses, are formed every secon...

By age two, a child has over one hundred trillion synapses, double th...

But compared to the rest of the animal kingdom, human brains are unusually incomplete at birth.

Every four months your red blood cells are entirely replaced, for instance, and your skin cells are replaced every few weeks.

Rather than memory being an accurate video recording of a moment in your life, it is a fragile brain state from a bygone time that must be resurrected for you to remember.

three diseases that are the most common causes of dementia: Alzheimer’s, stroke and Parkinson’s.

Bennett found that psychological and experiential factors determined whether there was loss of cognition.

cognitive exercise – that is, activity that keeps the brain active, like crosswords, reading, driving, learning new skills, and having responsibilities – was protective.

So were social activity, social networks and interactions, an...

Also protective

negative psychological factors like loneliness, anxiety, depression, and proneness to psychological distress were relate...

Positive traits like conscientiousness, purpose in life, and keeping ...

Your sensory organs – your eyes, ears, nose, mouth, and skin – act as interpreters.

The eyes convert (or transduce) photons into electrical signals.

Twenty percent of the calories we consume are used to power the brain.

electromagnetic radiation

Look up

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

Difficult concept

But visible light constitutes only a tiny fraction of the electromagnetic spectrum – less than one ten-trillionth of

All the rest of the spectrum – including radio waves, microwaves, X-rays, gamma rays, cell phone conversations, wi-fi, and so on – all of this is flowing through us right now, and

we’re completely unaware of it. This is because we don’t have any specialized biological receptors to pick up on these signal...

each creature perceives only what it has evolved to perceive.

But presumably, every creature assumes its slice of reality to be the entire objective world.

Reality is also odorless: there’s no such thing as smell outside our brains.

Synesthesia is a condition in which senses (or in some cases concepts) are blended.

There are many different kinds of synesthesia. Some taste words. Some see sounds as colors. Some hear visual motion. About 3% of the population has some form of synesthesia.

In some cases, a skill is so hardwired that the circuitry underlying it is found below the brain, in the spinal cord.

Consider rock climber Dean Potter: until his recent death, he scaled cliffs without a rope and without safety equipment.

Hm

Freud suggested that the mind is like an iceberg, the majority of it hidden from our awareness.

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.

Automatically opting employees into retirement plans (with the freedom to opt out if they’d like to) lea...

This view of governance is called sof...

“implicit egotism”, which describes our attraction to things that remind us of ourselves.

The men found the women with dilated eyes to be more attractive.

none of the men knew that dilated eyes are a biological sign of female arousal.

But their brains knew it. And the men were unconsciously steered toward the women with the dilated eyes, finding them to be more beautiful, happier, kinder, and more friendly.

men gave twice as much in tips when the dancer was ovulating (fertile) as when she was menstruating (not fertile).

men weren’t consciously aware of the biological changes that attend the monthly cycle – that when she is ovulating, a surge of the hormone estrogen changes her appearance subtly, making her features more symmetrical, her skin softer, and her waist narrower.