A human can always "see" their nose (assuming their eyes are open and they have a normal field of vision.)

Are We Always Looking at Our Nose?

Your nose is in your field of vision, so you are always looking at your nose. Luckily, our brains filter out sensory information we don’t need. The ability to ignore expected input is called “unconscious selective attention.” [1] [2]

You don’t walk around constantly noticing your nose or your glasses for that matter (if you wear glasses) because it’s not useful information. If nothing is changing with your nose, your brain will decide it doesn’t need to register it out of efficiency.

TIP: Other things we don’t notice include almost everything. Our attention can only focus on one thing at a time, and our short-term memory only holds about 5 – 7 items at once. If our brains couldn’t filter most of the world out, we wouldn’t be able to make sense of it. Learn about how memory works here; learn about the limits of attention here.

Vsauce, explores the wonky world of vision and sensory perception with “What Is The Resolution Of The Eye?”

FUNNY: Your brain is like an uncle who’s “got your nose”, but in a good way.

We are being bombarded with countless blips of visual information at all times, and our brain (mostly subconsciously) filters out everything we don’t need and makes composites of the sensory data to give us useful impressions of the world. We don’t take mental photographs; we store sensory-memory blips in sensory specific neurons and then create webs of connections between sensory data blips.

It’s a Matter of Efficiency

You don’t need to look at your nose or glasses all day long, so your brain filters it out. You don’t need to feel every part of your body 24/7, so your brain filters it out, you don’t need to hear your mom telling you to stop watching YouTube videos and clean your room, so your brain filters it out.

The brain is an efficient and calculating machine that continually tries to improve our efficiency. If our brain were less efficient, our bodies would have to eat more. The brain already takes up 20% of our energy even though it only accounts for 2% of our mass.

Sometimes this leads to strangeness, but in the case of our noses, let’s be glad for our limited attention and auto-magic filters.

TIP: Our brain loves shortcuts. One of its favorite types of shortcuts is “bias“. “Oh, we don’t need that information, so I’ll ignore,” says the brain without your input or awareness. “I have seen or experienced that this ‘type’ of people are usually bad so let’s avoid them,” etc. Everyone is chock full of bias.