This thread went viral because it’s fascinating and you’ll never see in quite the same way again
20.
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?
— foone (@Foone) July 3, 2018
21.
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!— foone (@Foone) July 3, 2018
22.
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.
— foone (@Foone) July 3, 2018
23.
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.
— foone (@Foone) July 3, 2018
24.
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!
— foone (@Foone) July 3, 2018
25.
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.
— foone (@Foone) July 3, 2018
26.
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.— foone (@Foone) July 3, 2018
27.
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.
— foone (@Foone) July 3, 2018
28.
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— foone (@Foone) July 3, 2018
29.
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.— foone (@Foone) July 3, 2018
30.
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.— foone (@Foone) July 3, 2018
31.
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
— foone (@Foone) July 3, 2018
32.
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.
— foone (@Foone) July 3, 2018
33.
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.— foone (@Foone) July 3, 2018
34.
(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.— foone (@Foone) July 3, 2018
35.
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.
— foone (@Foone) July 3, 2018
36.
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.
— foone (@Foone) July 3, 2018
37.
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.
— foone (@Foone) July 3, 2018
38.
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)— foone (@Foone) July 3, 2018
39.
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— foone (@Foone) July 4, 2018