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Peach...I could eat a peach for hours.
Saccadic Masking
It's the 40 or so minutes per day that you're effectively blind.
Quick, look at the wall to your left. When you flicked your eyes over there, for just a moment, you were blind. And you didn't even know it.
Ever watch a movie that gave you motion sickness, due to the camera whipping around too fast? This is what has some people puking during movies that use the "shaky handheld camera" gimmick (see: Cloverfield and The Blair Witch Project). Your brain doesn't like those rapid, blurry changes in vision.
But eye movements are even faster than those shaky camcorders. Flick your eyes over to the wall again. Notice you didn't get that nauseating, blurred image of the room zooming past your eye? That's because of saccadic masking.
In order to bring you this completely awe-inspiring view of what we're guessing is your cubicle wall right now, your brain rapidly moves your eyes without asking, in the neighborhood of three to five times per second. That's in addition to the times you move your eyes consciously, to look at the clock or the wall just now. To prevent your world from looking like the jerky Cloverfield camcorder all day, your brain shuts down your optic nerve while your eye is in motion.
The spooky part is the way your brain prevents you from noticing the blackness that occurs several times a second, every moment you use your eyes. Estimates vary somewhat, but it's likely that you're spending somewhere around 40 minutes a day with your eyes wide open, and totally blind.
Look at the wall one more time. If you make an effort, you can sometimes see a "flash" of darkness during a particularly long eye movement, one of those periods of blindness your brain insists isn't happening. But for the most part, your brain suppresses these flickers.