Where’s Your Blind Spot?

Did you know that your eyes have a blind spot near the center of your field of vision?

It’s true. I’ll prove it to you.

Together both of your eyes will cover the blind spot, but if you close one eye and look straight ahead, there’s a spot right in front of you where you can’t see anything. This is where the optic nerve connects to the back of your eyeball — a spot that’s devoid of light-receiving rods and cones.

However, you won’t see a dark spot because your brain will fill in the missing details. It smooths over what you don’t actually see.

Here’s a simple way to demonstrate it to yourself. Take a look at the line segments below — they should all be on the same horizontal line. You should see two gaps. Now close one eye and look at one of the gaps. If you close your left eye, then look at the right gap with your right eye. And if you close your right eye, then look at the left gap with your left eye. Position your head so your open eye is directly level with the gap, so you’re looking straight ahead at it.

___________ ________________________________ ___________

As you stare at one gap with your open eye, you should still be able to perceive the other gap within your field of view. Now keep staring at the first gap, and slowly move your head closer to the screen. At a certain distance (which for me is around 9-12 inches on my 19-inch monitor), you will see the second gap vanish. Remember that you have to keep staring at the first gap, so your eyeball isn’t moving too much. The second gap will disappear, and your brain will fill in the details to make you see a continuous line where the second gap is supposed to be.

If you find it difficult to do this on your screen, then draw the lines above on a piece of paper, and use the paper for the experiment. Then you can move the paper instead of your head.

Now if your brain does this with your vision, what does it do with the rest of your thoughts? Could it be smoothing over gaps in your understanding, causing you to have a blind spot you don’t even know about?