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foone
@Foone
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3. srp 2018. |
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The big obvious one being the blind spot. Vertebrate eyes are wired backwards so we've got a blind spot in each eye were the nerves enter into the eye. About 6 degrees of your vision in each eye is just not there, as there's no light sensitive cells there.
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foone
@Foone
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3. srp 2018. |
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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.
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foone
@Foone
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3. srp 2018. |
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Here's another one: You can see in color, right? (well, some of you can't. Sorry)
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 pic.twitter.com/Xf7sGgtdtx
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foone
@Foone
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3. srp 2018. |
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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.
But I bet if you shift your attention to your peripheral vision right now, it's in color.
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foone
@Foone
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3. srp 2018. |
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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. pic.twitter.com/3rV3uTZypf
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foone
@Foone
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3. srp 2018. |
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There's 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?
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foone
@Foone
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3. srp 2018. |
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now repeat the experiment but ask them to try to hit the balls back with a bat, and suddenly all the estimates shift larger.
They actually see the ball as bigger because they need to hit it. their vision is exaggerating it to make it easier to see!
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foone
@Foone
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3. srp 2018. |
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which just goes to show, like I said, your vision is not a camera. perfect accuracy is not one of its goals. it does not give any shits about "objective reality", that's not important.
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foone
@Foone
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3. srp 2018. |
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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.
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foone
@Foone
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3. srp 2018. |
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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 screw with your sense of time passing, just to make up for visual defects. NOPE!
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foone
@Foone
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3. srp 2018. |
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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 those moments. But you still think you are seeing.
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foone
@Foone
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3. srp 2018. |
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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 in it.
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foone
@Foone
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3. srp 2018. |
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And for fun, here's wikipedia's example of the blindspot.
Stare at L with only your left eye, adjust the distance, and the R will disappear. You don't see "nothing" or "black", you see the background, because you expect to. pic.twitter.com/NBN485EOvC
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foone
@Foone
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3. srp 2018. |
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This is why laser damage your retina can be so insidious. Your visual system already can hide "holes" in your vision, what's one more to hide?
So you damage a small spot of your retina and your visual system covers it up.
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foone
@Foone
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3. srp 2018. |
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but since you didn't go "WELL THAT WAS TERRIBLE I BETTER TAKE BETTER CARE OF MY EYES" and stop fucking with lasers, you keep doing it
eventually you accumulate so much damage that your visual system simply cannot manage hiding it all and your vision rapidly degrades.
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foone
@Foone
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3. srp 2018. |
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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
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foone
@Foone
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3. srp 2018. |
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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.
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foone
@Foone
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3. srp 2018. |
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Anyway, back on 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 had started "flipping" the image.
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foone
@Foone
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3. srp 2018. |
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(I say flipping in quotes because it's not as simple as it started showing the pixels at the top row on the bottom row, cause our vision doesn't work like that)
It only took them a few hours to get back to normal after taking these glasses off, though.
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foone
@Foone
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3. srp 2018. |
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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.
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foone
@Foone
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3. srp 2018. |
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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.
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foone
@Foone
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3. srp 2018. |
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because if they only move during saccades, we never see them moving. and since so much of our vision is based on just filling in what we think is there, if they stay out of the direct center of our vision, we'll just visually fill them in, like they were never there.
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foone
@Foone
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3. srp 2018. |
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Check it out if you're into hard SF stories of first contact. It's got some really neat ideas about human vision, very unique aliens, the nature of conciousness, 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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foone
@Foone
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3. srp 2018. |
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BTW, remember how I said "vertebrate eyes" up there?
Guess who has eyes which are wired forwards instead of backwards (no have no blindspot), have an internal lens, and can even see polarization of light?
our good friends the Cephalopods! pic.twitter.com/SOMT5CB2SY
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