The illusion of reality
From the moment you awaken in the morning, you’re surrounded with a rush of light and
sounds and smells. Your senses are flooded.
All you've got to try and do is show up daily, and
without thought or effort, you are immersed in the irrefutable reality of the world.
But how much of this reality is a construction of your brain, taking place only inside
your head?
Consider the rotating snakes, below. Although nothing is actually moving on the page,
the snakes appear to be slithering. How can your brain perceive motion when you know
that the figure is fixed in place?
Nothing moves on the page, but you perceive motion. Rotating Snakes illusion
Or consider the checkerboard
Or consider the checkerboard above.
Although it doesn’t look like it, the square marked A is exactly the same color as the
square marked B. Prove this to yourself by covering up the rest of the picture. How can
the squares look so different, even though they’re physically identical?
Illusions like these give us the first hints that our picture of the external world isn’t
necessarily an accurate representation.
Our perception of reality has less to try and do with
what’s happening out there, and more to do with what’s happening inside our brain.
Your experience of reality
It feels as though you have direct access to the world through your senses. You can reach
out and touch the material of the physical world – like this book or the chair you’re
sitting on. But this sense of touch is not a direct experience. Although it feels like the
touch is happening in your fingers, in fact it’s all happening in the mission control center
of the brain. It’s the same across all your sensory experiences. Seeing isn’t happening in
your eyes; hearing isn’t taking place in your ears; smell isn’t happening in your nose. All
of your sensory experiences are taking place in storms of activity within the
computational material of your brain.
Here’s the key: the brain has no access to the world outside. Sealed within the dark,
silent chamber of your os, your brain has never directly experienced the external world,
and it never will.
Instead, there’s only one way that information from out there gets into the brain. Your
sensory organs – your eyes, ears, nose, mouth, and skin – act as interpreters.
They detect
a motley crew of data sources (including photons, air compression waves,
molecular concentrations, pressure, texture, temperature) and translate them into the
common currency of the brain: electrochemical signals.
These electrochemical signals dash through dense networks of neurons, the main
signaling cells of the brain.
There ar 100 billion neurons within the human brain, and
each neuron sends tens or hundreds of electrical pulses to thousands of other neurons
every second of your life.
Neurons communicate with one another via chemical signals called neurotransmitters. Their
membranes carry electrical signals rapidly along their length. Although artistic renditions like this one
show empty space, in fact there is no room between cells in the brain – they are packed tightly against
one another.
Everything you expertise – each sight, sound, smell – rather than being a direct
experience, is associate chemistry rendition in an exceedingly dark theater.
How will the brain flip its Brobdingnagian chemistry patterns into a helpful
understanding of the world? It does so by comparing the signals it receives from the
different sensory inputs, detecting patterns that allow it to make its best guesses about
what’s “out there”. Its operation is so powerful that its work seems effortless. But let’s
take a closer look.
Let’s begin with our most dominant sense: vision. The act of seeing feels so natural that
it’s hard to appreciate the immense machinery that makes it happen. About a third of the
human brain is dedicated to the mission of vision, to turning raw photons of light into our
mother’s face, or our loving pet, or the couch we’re about to nap on. To unmask what’s
happening under the hood, let’s turn to the case of a man who lost his vision, and then
was given the chance to get it back.
I was blind but now I see
Mike May lost his sight at the age of three and a half. A chemical explosion scarred his
corneas, leaving his eyes with no access to photons. As a blind man, he became successful
in business, and also became a championship paralympic skier, navigating the slopes by
sound markers.
Then, after over forty years of blindness, Mike learned about a pioneering stem cell
treatment that might repair the physical harm to his eyes.
He decided to undertake the
surgery; after all, the blindness was only the result of his unclear corneas, and the
solution was straightforward.
But something unexpected happened. Television cameras were on hand to document
the moment the bandages came off. Mike describes the experience when the physician
peeled back the gauze: “There’s this whoosh of light and bombarding of images on to my
eye. All of a sudden you turn on this flood of visual information. It’s overwhelming.”
To test time perception in frightening situations, we dropped volunteers from
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