this post was submitted on 24 Sep 2023
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Eyes don't really have a concept of FPS because we don't have shutters in the first place. The brain is just continuously interpreting what we see. And it fills in a lot of gaps: for example, we technically have a large blind spot right in the middle of the retina, and that's why we're more sensitive to movement in our side vision.
Cats see just fine in the dark, our eyes are just not sensitive enough to low light to be all that useful for us, but we could, if the eyes provided that input. Evolution just made it so we favored speedy and sharp vision in daylight rather than night vision, in part because we quickly developed technology (fire) to keep our areas lit as needed.
You're conflating the blind spot and the macula there.
We do not have a blind spot in the middle of the retina. If that were the case it would be pretty problematic for vision. What we do have is what's called the Macula, an area of high concentration of cones and low concentration of rods. Cone cells give us highly detailed color vision, while rod cells only give us overall brightness, but are much more sensitive to light. That's why, as you mention, we're more sensitive to movement in our peripheral vision, and also why the center of our vision performs way worse in very low light situations. (Ever seen a faint star that seems to vanish when you try to look right at it? That's why)
We do actually have a fully blind spot, but that one sits not at the center of the retina, but off to the side. It's where the optic nerve enters the retina, and it doesn't have anything to do with better/worse perception of movement, it's just fully blind and always gets interpolated by the brain, it literally fills it up with what it thinks should be there. If you get a small object right into that spot for one eye and cover the other eye, it will just disappear.
But cats have even faster sight. I think the avg reflex time for a cat is around 70-80ms while humans are over twice that. So it seems like their vision is entirely better. Why didnβt our eyes evolve to be like theirs?
Feline vision has drawbacks, and some adaptations we don't.
For one, cats have reflective eyes, rather than absorb light, that misses any cones/rods, cats reflect it back out, passing the light that comes into their eyes through their retinas twice. This improves how much of the light actually hits the light sensitive cones and rods in their eyes.
Second, cats have slitted pupils, this means they have a MASSIVELY larger range of light they can adjust to let into their eyes. Slitted pupils are able to close much tighter, and open much wider, than circular ones. If you've ever seen a cats eye in the dark, you know their pupils get HUGE. Several times that of humans.
As for a drawback, cat eyes suck at focusing. All cats are far-sighted. At less than about 20 cm, cats cannot see. All they get is a blurry mess. Ever wondered why your cat seems completely clueless when you set down a treat right in front of it? That's why.
This is why cats have whiskers. Close up, they go 100% by smell, hearing and feel!
Are vampires just big kitties?
Why is your account marked as a bot?
... dunno?
It's a checkbox you set in your user settings. Is it checked?
it was. I'm not the smartest person alive so it checks out
Ur still marked as a bot. Did you hit save after unchecking it?
yep, it's deselected now
Ah, checked your profile from your instance, not a bot anymore, looks like it's just slow to update on mine.
Woa... you just made me wee bit smarter with this
*cries in intelligent design*
Because our sight was never enotofna disadvantage that the humans with bad vision got killed off fast enough and the ones with better vision got to procreate more. Simple as that.
Well yeah, every animal has different features which make assist it to exploit whichever evolutionary niche it inhabits.
Maybe maintaining such fast reaction times just isn't possible with larger brains, or higher executive functions.
For that matter, phones don't have shutters either.
They have electronic shutters
And by blind spot, youβre referring to the small portion of the vision that sees color and is much much much less sensitive to light (thus horrible at night vision) right?
No, we have a spot in each eye that is not sensitive to light at all because the space is used up by the optic nerves: https://www.scientificamerican.com/article/find-your-blind-spot/
To add to this thereβs a theory amongst creationists that we must be of intelligent design because the eye is so complex and perfect. Not only is this wrong because of the blind spot but another species developed eyes separately and they donβt suffer the same blind spot problem! Notably the nerve channels in octopus eyes allow full coverage.
Wiki: https://en.wikipedia.org/wiki/Cephalopod_eye Illustration: https://commons.wikimedia.org/wiki/File:Evolution_eye.svg
That one does not sit in the center of the retina though, and doesn't have anything to do with higher motion-sensitivity in your peripheral vision. The macula, which the other commenter describes, is what's responsible for that, and it's a different thing than the blind spot.
Oh yeah, forgot about that