“Your reality is what you expect!” -How the brain manipulates our vision?

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How do we watch a beautiful sunset or a thriller NetFlix movie? I mean, what’s the mechanism behind vision? The answer is high school stuff, isn’t it? A stream of photons hitting on our retina, generating electric impulses to communicate with our visual cortex from where the brain constructs a visual form of an irrefutable reality around us. Right? We always thought that our brain continuously decodes all these raw data acquired from our eyes, to enable an uninterrupted construction of reality. But this simple model of vision is sadly wrong!

Many of us think that our perception of the world is outside-in, i.e., whatever happens outside of our brain is what we always perceive. But, the truth is that we perceive things in the way we expect! Our perception of this world is inside-out, i.e., the world we see around us is mostly an illusion created by our brain based on our expectations. Let’s begin to change the way you see this world.

Before jumping into the details, have a look at the two examples below:

  1. There was a maximum-security federal prison on Alcatraz island, near Sans Francisco. More interestingly, there was a particular cell called “The Hole”, wherein only notorious prisoners were sent. ‘The Hole’ is a pitch-black cave-like place where light and sound are entirely cut-off. If you are trapped inside, you are going to bang your heads on the wall for some peaceful moments! Once, a famous neuroscientist named Dr David Eagleman got an opportunity to talk to one of the prisoners who had spent some time inside the Hole. The prisoner describes his experience as, “Although I didn’t see any light or sound initially, I gradually started to experience weird things. I remember going on these trips. One I used to see was flying a kite. It got pretty real. But they were all in my head.” Another prisoner he interviewed even watched a TV show without any subscription! They were not daydreaming, they saw everything for real!
  2. Imagine that you are shooting a video of a landscape with your mobile. Instead of smooth panning, you are instructed to move the camera precisely as your movement of eyes. As you probably know, your eyes always undergo tremulous movements called saccades (i.e., slight random motion of your eyeball). If you are to shoot this way, you will find your recorded video rapidly lurching and highly unstable. But with our eyes, amid saccades, we see a quite steady and stable landscape around you.

Before diving into the specific reasons for the above cases, let’s understand the science behind vision: it’s called the “internal model” of reality.

The science behind vision: In this model, the brain creates its own reality irrespective of the signals sensed. This happens because of a small portion of the brain called thalamus that acts as a hub to transmit and receive signals from both visual cortex and eyes. The visual cortex assumes a model of reality based on our previously accumulated experiences. This model of reality is then passed to the thalamus, wherein the signals from the eyes are received. Now, the thalamus compares the brain’s expected reality with the visual signals from the outside world. If they match (“when I look at the table, I should see my mobile phone”), very little information is sent back to the visual cortex. This way, the thalamus only sends back the difference (also called “error”) between the internally predicted model and the signals from eyes to the visual cortex. This “error” updates the expected reality (the internal model) to eventually form what we call the vision. So, what we see relies mostly on our expectation, not on the stream of photons hitting on the retina. We are blissfully unaware of this complex process happening inside our brain.

How did the brain manipulate the prisoner’s reality? Now, it’s time to demystify the reasons behind the two cases above based on the internal model. When the prisoners were in the Hole, they were unable to sense anything from outside. So at some point, the brain’s internal model takes over the show, with no “error” data to interpret. Therefore, the prisoners saw what they expected even after removing the entire world out of them.

In the second case, our internal model of reality assumes that the world is stable. Our eyes have only one job; feeding new information continuously to the thalamus to update the internal model. No data that questions the stability of the world is fed from the eyes. So, our brain keeps the postulate that the world is stable, and we experience a stable world irrespective of the lurching movement of eyes!

Do you want to experience the “internal model” in action? It’s simple! Take a Halloween mask and rotate it in front of your eyes. When you look at the front side (projected side) of the mask, we can easily interpret it as a face. Further, if you look at the backside (hollow side) of the mask, it still looks like the mask is projected towards you. And, you can still see a face. This is because your brain expects a face on the mask, and the minimum “error” data enables us to see a face on both sides of this mask. See the picture below:

Hollow mask illusion: The projected (front) and hollow (back) sides of the same mask give the same impression of a face.

No one can ever perceive the objective reality in the way it is. All of us assume our own slices of reality based on our expectations. Yes! What you see is only your private matter, to which no one can ever interfere! Your brain lights up this universe, and in that sense, “you create your private reality”. So, why don’t’ you enjoy this privacy at every moment?

Reference: Book, “The brain: Story of you” by Dr. David Eagleman.

Note: When I say, “you create your private reality”, I mean that your apparent perception of the world through your senses is different from others. I don’t mean the “objective reality” described by science.

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