The brain is pretty cool
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Someone calling himself "Foone" posted some stuff about how human vision works with dozens of twitter posts, which was shared with dozens of screen shots on Imgur. Crustysmegma asked "can someone put this into a format that isn't Twitter?"
Here goes:
Quote:
You want to know something about how absolutely insane our brains are? OK, so there's a physical problem with our eyes: We move them in short fast bursts called "saccades," right? Very quick and synchronized movements.
The only problem is: They go all blurry and useless during this. Having your vision turn into a blurry mess every time you move your eyes is obviously not a good idea, so our brains hide it from us. Now imagine you're an engineer and you have this problem. You've got some obvious solutions you could do.
1. Make the vision go black during movement. Some VR games do this!
2. Just keep showing the last thing we saw prior to movement.
Both are good options with different downsides, but oh no! This is assuming everything makes sense and is chronological and (regular) logical. Your brain does neither of these options, really. First, it basically puts your visual system on pause. You're not seeing blackness or even nothing, you're just not seeing period. Then when you finish your saccade, it shows you what you now see at the new position and then it pretends it can time travel.
It seriously shows you the image at the new point, but time-shifts it backward so that it seems like you were seeing it the whole time your eyes were moving, and because your brain is not a computer with a consistent clock, this works.
You can see this effect happen if you watch an analog clock with a second hand. Look away (with just your eyes, not your head), then look back to the second hand. It'll seem like it takes longer than a second to move, then resumes moving as normal. That's because your freaking visual system just lied to you about how long time is in order to cover up the physical limitations of those chemical camera orbs you have on the front of your face.
We've known about this effect for over 100 years, it's called "Saccadic masking," and more specifically Chronostasis. Your visual system lies to you about when things happen by up to half a second(!) just to avoid saccades blurring everything.
So, while I firmly believe we're basically just overgrown biological computers, we're apparently computers programmed by completely insane drunkards in Visual Basic 5 and you might think "Hey wait, wouldn't my vision pausing for half a second have all kinds of weird effects on moving objects? Why don't they appear to stutter when moving?" The answer is simple! Your brain has even more ugly hacks on top of this to avoid you seeing that. If you've got a clock where the second hand doesn't tick, but instead smoothly rotates you won't see this because your brain recognizes it's moving and adjusts what you see to make sure it sees the right thing. It's only really obvious with periodically moving things like a clock hand because it's not moving (so not triggering the movement-during-chronostasis hack), but it moves at a set rate, so you can notice that rate appearing to change.
It's tempting to think of your eyes and visual system as a camera just dumping a video feed into your conscious brain, but that's absolutely not the case. What you think you see and what your eyes actually see are two exceptionally different things.
The big obvious one is the blind spot. Vertebrate eyes are wired backward so we've got a blind spot in each eye where the nerves enter into the eye. About 6 degrees of your vision in each eye is just not there as there are no light sensitive cells there. Do you see a blind spot right now?
No, you probably don't. Close one eye! There's now no way for the other eye to fill in the gaps. Still, no blind spot. Your visual system is lying and making up content it thinks is there. You literally cannot see what you think you see.
Here's another one: You can see in color, right? (Well, some of you can't.
Sorry, eh) You can see in color all throughout your vision, it's color everywhere?
Well, most of your cone cells (which are sensitive to color) are in the fovea, a little spot in the center of your vision.
http://ecomodder.com/forum/attachmen...1&d=1530697978
So, outside of that center-of-vision spot you have very little color perception. There's some, but it's very limited compared to your main color vision. Your vision system is lying. It's remembering what colors things are and guessing and filling in the gaps. It's basically doing a Ted Turner colorization process on your non-central vision.
http://ecomodder.com/forum/attachmen...&d=15306955 76
There are even weird effects like what's called "Action-specific perception." If you get a bunch of white balls of various sizes and toss them at people, then ask them to estimate the size of the balls thrown at them, they'll have a certain size estimate, right? Now repeat the experiment, but ask them to try to hit the balls back with a bat and suddenly the all the estimates shift larger. They actually see the ball as bigger because they need to hit it. Their vision is exaggerating to make it easier to see!
Which just goes to show, like I wrote, your vision is not a camera. Perfect accuracy is not one of its goals. It does not care about objective reality. That's not important. What's important to the evolution of the visual system is any trick that helps you survive, no matter how dumb or weird it is. So if you want an accurate visual representation of what things look like use a camera, not your eyes.
In any case the original point was that while you might know this about your eyes being poor cameras that lie to you, you might still think that at least they're consistent time-wise. They don't mess with your sense of time passing just to make up for visual defects. Nope!
If you can't get it done in time, turn back the clock, and pretend you did. That's a perfectly good solution when you're the visual system.
BTW, Hierarchon reminded me of a neat trick with saccadic masking: Go look in a hand mirror. No matter how close you bring it to your eyes and how much you look around, you will never see your eyes move. You're blind during these moments, but you still think you are seeing. She additionally pointed out that your phone's selfie mode is not a mirror and it has a slight delay, so you can see your eyes moving. For fun, here's a Wikipedia example of the blind spot. Stare at the L with only your left eye, adjust the distance, and the R will disappear. You don't see nothing or black, see the background because you expect to.
http://ecomodder.com/forum/attachmen...1&d=1530696779
This is why laser damage to your retina can be so insidious. Your visual system already hides holes in your vision. What is one more? So, you damage a small spot of your retina and your visual system covers it up, but since you didn't think "Well that was terrible, I better take better care of my eyes!" and stop messing with lasers, you keep doing it, and eventually you accumulate so much damage that your visual system simply cannot manage hiding it all and your vision rapidly degrades.
The other reason lasers are so dangerous is that they don't necessarily trigger the same responses as regular incoherent light. Your pupil reflex is only triggered by some special cells in the center of your eye, so an off-center laser might not cause your iris to contract and infrared laser light is just as dangerous as visible laser light, but can't trigger your blink reflex. Your eyes automatically close when exposed to bright light, but they can't detect infrared light. Despite not seeing it, it still causes damage.
Anyway, back to how amazing and crazy your vision is: There was an experiment back in 1890 where someone wore glasses made with mirrors in them to flip their vision. After about 8 days they could see just fine with them on. Their vision system started flipping the image. It only took them a couple of hours to get back to normal after taking off these glasses, though.
The last really fun part about this flipping experiment: Your eyes already do it. Based on how our vision is wired, we should be seeing everything upside-down. We don't, but only because our visual system has had our whole life to adapt to this.
BTW, since a few people have brought it up: There's a great sci-fi novel by Peter Watts called "Blindsight." In it humans encounter an alien race they call Scramblers who can move very fast and precisely and they exploit saccades [...].
Check it out if you're into hard SF stories of first contact. It's got some fascinating ideas about human vision, very unique aliens, the nature of consciousness, the future of humanity in the face of perfect VR, and vampires. (Really, it has vampires, while still being hard SF)
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