Blind Spots
essay by Ziya Tong
HUMANS HAVE A TENDENCY to think we have an accurate picture of the world, but often we’re wrong. That’s because every person is born with a blind spot. In fact, we have two: one in each eye.
In the same way that you would be unable to see all of the movie screen if you were given a crummy seat behind the projector at a theatre, situated at the back of your eyeballs there’s an area where light receptors do not grow, because it’s the exact spot where the optic nerve jacks into your brain. And yet, despite the fact that the area it eclipses is relatively large (nine full moons in the sky could fit in this broken field of view), most of us never even notice it.
The best way to see what you cannot see is with your own eyes. So let’s take a look. Cover your left eye and use your right eye to look at the dot above. Now, with your eye still trained on the dot—staying aware of the cross but not focused on it—begin to move your head slowly towards and away from the screen. You should notice that at a certain point the cross suddenly vanishes; it disappears from sight. You can do the same with your left eye focused on the cross; the circle will vanish at a certain point.
Remarkably, this blank spot doesn’t register as some sort of void. Instead, our brain compensates for the emptiness, and with our own perceptual version of Photoshop it even fills in the right background color. Our blind spots are perfectly camouflaged.
We are blind to our blindness.
Now, you might think that a blind spot this obvious would have been detected long ago, but it wasn’t until a French physicist named Edme Mariotte was dissecting an eye and came across the bundle of nerves connected to the retina, that he wondered if it might be blocking our sight. Doing some vision tests with his own eyesight, he discovered what was soon to become a mini-sensation in the 1600s. It delighted the nobles of the royal court, who revelled in the magic trick of making each other disappear without blinking an eye.
Of course, blind spots are not only in our eyes; they are also in our surroundings. The French for “blind spot” (angle mort or "death angle") says it all: every year in the United States alone, 840,000 car accidents happen because we can’t see something very large driving at us until it crashes into our field of view.
Tong, Ziya.
The Reality Bubble:
Blind Spots, Hidden Truths, and the Dangerous Illusions that Shape Our World.
Penguin Canada, 2019.
The Reality Bubble:
Blind Spots, Hidden Truths, and the Dangerous Illusions that Shape Our World.
Penguin Canada, 2019.