The human eye has a “blind spot.” This is a fascinating topic, since it is one of those things that we don’t usually notice as we go about our day to day lives. But at the same time, when we do notice it, it can be a little startling.
The reason we have this blind spot is because of the “optic disc.” This is where the optic nerve meets your retina. Photoreceptor cells are nonexistent here, which is why images vanish when they hit this spot.
So if we have a small blind spot on each eye, why do we not have “holes” in our vision? This is because both our eyes work to cover the blind spot of the other, so generally we never even notice. The blind spot experiment shows us why our eyes work correctly..
Finding the Blind Spot
This is a fun experiment to do just to experience the blind spot experiment and see how it works – or doesn’t work, as the case may be. The easiest way to locate it is to take a piece of paper and draw a square, and then a few inches away, draw a circle. You could also use something like shapes made of construction paper, or stickers. Just be sure both shapes contrast against the paper nicely.
Once you have your two points separated by three or four inches, hold the paper as far out as you can, and close your right eye. Keep your left eye on the circle, and bring the paper closer slowly. At some point, the square will vanish, and you will know you have found the blind spot in that eye. Now you can repeat this process with your other eye, looking at the other shape.
When the shapes vanished, what you saw instead was the color of the paper. Our brains are marvelously wired to fill in our blind spots in this way. This will work on any color of background, and it will even work on shapes. For example, if you draw two long rectangles that have a break or circle in between them, and you try this experiment again, looking at a shape a for inches to the side, the circle will vanish, and the two rectangles will suddenly be linked.
Your brain could not “see” the circle, so it just finished the shape it saw around the spot.
Try this blindspot experiment with your original piece of paper, but this time surround one of the shapes with shapes in a different color. Your brain will fill in this new color!
While our blind spot isn’t something that affects our daily lives, it is still a fascinating topic, and worth experimenting with. It really shows us how amazing our brains are!