Try this. Close one eye and glance toward the middle of your face. There it is: a soft, blurry shape at the edge of your view. That's your nose, and it's been there your whole life. So why don't you see it all the time?
Here's the short answer: your nose sits in the field of view of both eyes, but processing in your brain keeps you from noticing it during normal seeing. It's part of a broader habit. Your senses tend to tune out things that never change, and your nose is always in exactly the same spot. So your brain quietly edits it out, until you go looking for it.
Your Nose Is Always in the Picture
Each eye takes in a wide view. Toward the outside, a single eye can see roughly 107 degrees from straight ahead. Toward the nose, it reaches only about 60 degrees. Your nose sits right there in that inner part of the view, for both eyes.
That means a bit of nose sits inside each eye's view at all times. When you close one eye, the trick is easier to notice, because you're paying attention to an unusual view instead of your normal two-eyed picture.
The Brain's Editing Room
Scientists call one part of this neural adaptation. When something stays exactly the same, your senses gradually respond to it less and less. Rest your hand on a table and you feel the surface right away. A little later, you hardly notice it at all. The same goes for a small piece of paper dropped on the inside of your forearm. You feel it briefly, and then the sensation fades away.
Vision does something similar. In an effect called Troxler's fading, if you stare at one point, an unchanging object off to the side can fade away and seem to disappear. It was first described by Swiss physician Ignaz Troxler in 1804, and research suggests at least part of it happens in the brain. Your ever-present nose is a natural candidate for this kind of fading.
Another Hole You Never Notice
Your nose isn't the only thing your brain hides. Each eye also has a blind spot. It's where the optic nerve passes through the back of the eye, a spot with no light-detecting cells at all.
You'd think that would leave a dark hole in your vision. Instead, your brain fills it in, using surrounding detail and information from your other eye, so you never notice the gap.
The blind spot was first documented in the 1660s by Edme Mariotte in France. At the time, people assumed that spot should be the most sensitive part of the eye, so his discovery came as a surprise. Interestingly, octopuses and squid don't have this blind spot, because their eyes are wired from behind.
Why Tuning Things Out Helps
All of our senses are built to notice change. That's useful. If your brain kept shouting about your nose, your clothes, and the chair beneath you, it would be harder to notice a car turning the corner or a friend waving hello.
So if you're suddenly very aware of your nose right now, don't worry. Give it a few minutes, and your brain will tuck it neatly back out of sight, right where it's been all along.
