Comments
AbouBenAdhem OP t1_iuchfr1 wrote
Cats have better night vision than we do because they’ve traded cone cells for rods—so they have higher resolution and dynamic range in their grayscale vision at the expense of being red/greed colorblind.
But if you scaled up a cat’s eye to human size, it seems like it should be even better—similar to a camera with a bigger objective lens and/or ccd. Unless I’m missing something?
[deleted] t1_iuchyzj wrote
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burjua t1_iucmjfo wrote
The size doesn’t matter. Birds evolved much better vision than humans but their eyes much smaller in many cases
WesleyRiot t1_iucrjub wrote
Cats have better night vision because of a reflective layer at the back of the eye that means light hits their retina twice. Or am I thinking of dogs? Or is it the same
amaurea t1_iucru29 wrote
That layer is called the tapetum lucidum, and helps with sensitivity, but comes at the cost of resolution, making their vision blurrier than it otherwise would be.
[deleted] t1_iuczp7t wrote
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Substantial-Turn4979 t1_iud1j32 wrote
Better or poor are tricky descriptors. Animals evolve their senses to be suited to their environments. Humans’ colour vision is amongst the best in the world and have some of the most detailed up close vision in bright light. The trade off was poor low light vision. Other animals prioritize low light vision over perceiving colours. Humans have sharp vision in a tight area directly in front of them but the trade off is poor peripheral vision and no vision behind them. Other animals have an almost 360 degree field of view, but lack a region of extreme sharpness. Each of these different sets of abilities is “better” in a particular set of living conditions.
AbouBenAdhem OP t1_iuddzsu wrote
> The size doesn’t matter.
Real estate inside the skull is expensive, evolutionarily, and humans have sacrificed a lot to maximize brain volume. If it were possible to see as well with bird-sized eyes, why haven’t we already evolved them in exchange for bigger brains?
MalevolentlyInformed t1_iudge6t wrote
>Humans’ colour vision is amongst the best in the world
Slight nitpick: humans have some of the best color vision among mammals. But most vertebrates see more color gradation than we do. Reptiles, fish, amphibians, and birds are mostly tetrachromats, vs apes/Old World monkeys (trichromats) and other mammals (dichromats). Some invertebrates also have "better" color vision than us.
[deleted] t1_iudh4ro wrote
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Substantial-Turn4979 t1_iudlfdj wrote
I was aware of birds and monkeys, but not reptiles and amphibians. Cool! Thanks for the nit pick.
Dirty_Hertz t1_iudmkb9 wrote
Doesn't the mantis shrimp have the widest range of color vision including UV of any animal?
Dirty_Hertz t1_iudns9v wrote
One thing you are kind of approaching here is the fact that evolution has no "purpose" other than increasing fitness with the tools it has available (previous adaptations and random mutations).
It's possible that bird eyes would be more advantageous than ours, but we diverged from them long ago and going back would be pretty difficult with potentially no useful steps in between
MalevolentlyInformed t1_iudoi93 wrote
I don't know if it's the widest but it's certainly crazy. Anywhere from 8-15 to our 3 cones lol. Plus some can see linear and circular polarized light.
FrumundaCheeseGoblin t1_iuds7pj wrote
Also, evolution doesn't result in "perfection". It results in "good enough".
ImprovedPersonality t1_iudszit wrote
But how good is their resolution? Having different cells takes up space.
ImprovedPersonality t1_iudt5xr wrote
Still takes up a big volume of their heads. If they could be smaller they’d probably would be.
Resident_Skroob t1_iudt7tb wrote
Whoa. What? To the last sentence.
[deleted] t1_iudyht8 wrote
GeriatricZergling t1_iue3iab wrote
>The size doesn’t matter. Birds evolved much better vision than humans but their eyes much smaller in many cases
Incorrect. A larger eye will simply have more photoreceptors per degree of optic field, allowing a higher-resolution image, all other things being equal. If you are small (e.g. most birds), you can compensate by packing them more tightly, but this comes at an energy cost (photoreceptors are expensive).
ejdj1011 t1_iue67ja wrote
Yeah, but the way their optical perception is wired, they still have worse color perception than humans. Basically, each cone (color sensor) a mantis shrimp has only sees a very narrow band of wavelengths. If a mantis shrimp has 15 cones, it can basically only see 15 specific colors. So while humans only have 3 cones, they overlap heavily and our brains can process the ratio of signals to mix colors.
gphrost t1_iueanah wrote
That's a fun thought experiment. I'm sure there are well thought out theories. What would happen with a long enough amount of time? Just cycles of different eco-forms, or would it culminate into the "perfect" living creature
Cheetahs_never_win t1_iuegrp8 wrote
Imagine a sine wave to represent a photon. The sine wave is 2d. Now Imagine being able to rotate the sine wave around the neutral axis. To us, the light looks the same. To them, the light looks different.
Normal light is a bunch of these waves at different frequencies and adjusted forwards/backwards in a random fashion.
If you could adjust them such that they're all aligned, which we can do with certain materials that block light paths that come in at the "wrong" angle, but turn the intensity back up, you and I can't tell the difference between the before/after. They can.
And I guess we might not have the vocabulary to describe what they see, but there are some women who are tetrachromats who basically describe colors and patterns only fellow women tetrachromats can see.
Coomb t1_iuehpas wrote
We did evolve smaller eyes when we transitioned to being diurnal hunters.
https://www.sciencedirect.com/science/article/abs/pii/S0047248406002053
One thing you may be missing which is probably relevant here is that, all other things being equal, a smaller eyeball means a larger depth of field. That is, more of the visual field measured along the axis of sight will be in approximate focus the smaller the eyeball. This might sound like a desirable property, and in some cases it is. But it reduces your ability to determine target distance through adjusting the optical properties of the eye, for example by flexing the lens or adjusting the pupil diameter. When you focus on something in the nearfield or midfield, with a smaller depth of field you get more information about the relative position of a target and its visual background than you do with a larger depth of field. In the case of a pinhole aperture which has, in theory, unlimited depth of field, you get no information at all about the distance to any of the objects in the scene based on their relative sharpness because everything has the same sharpness.
For diurnal raptors, for example, a large depth of field isn't much of a disadvantage because they're trying to acquire relatively small targets which are relatively far away and are pretty much always just about the same distance away as their visual background. If you're looking at a rabbit from above you don't need to have optical information to know that the rabbit is just about as far away as the ground. On the other hand, if you are a diurnal ape operating along the surface of the Earth looking at the horizon, and your typical hunting targets are at most single to double-digit meters away when you begin your attack, and which is often hunting targets with complicated backgrounds at different distances away, it's pretty important to have the ability to distinguish how far away your target is in an absolute sense, as well as how far it is from its background. A larger eyeball, which, all other things being equal, gives you a smaller depth of field, helps in that aspect.
In general, our brain does quite sophisticated visual processing on the information it receives from our eyeballs. [In fact, the image processing is so sophisticated that it allows us to surpass the physics of our eyes in some sense under certain conditions.] (https://en.wikipedia.org/wiki/Hyperacuity_(scientific_term)) Obviously we are not actually breaking physics with our eyes, but taking advantage of the fact that we have a matrix of receptors and combining the signal from more than just one to provide information at a finer resolution than would be possible if one simply naively took the intensity values recorded by each receptor and displayed them without processing. One could argue that perhaps shrinking the eyeball would free up some space in the cranium for more brain, but in order to maintain the same visual abilities one would probably need to devote more of the brain to visual processing.
[deleted] t1_iuel70w wrote
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86BillionFireflies t1_iufkea0 wrote
The key piece of information that's often left out is that their color vision is actually terrible.
Picture a movie playing in color. Now picture three black-and-white movies playing side by side: one showing the red channel, one showing the green channel, one showing the blue channel. Same information, but there's a lot of stuff your brain can't actually SEE if the information isn't combined the right way.
The mantis shrimp doesn't combine information across color channels the way we do, for a simple reason: its expensive. It takes a lot of extra neurons to combine different cone inputs in a way that lets you see what we know as color, and neurons cost calories.
Dorocche t1_iug09yc wrote
How do we know that the shrimp doesn't do that? We can't observe their qualia obviously.
googlecansuckithard t1_iug6ona wrote
It depends upon species of animal - not all small animals have good vision, and its not necessarily consistent to phylogenic order and family. For example Aphonopelma sp. and bracypelma sp. Have poor vision, where Atrax sp., Theraphosa sp., Muisuelena sp., and Hognas sp. Have strong accute vision, despite all being members of the same order.
86BillionFireflies t1_iuhghij wrote
We can do (and have done) experiments to determine how well they can distinguish one color stimulus from another, and they perform worse than humans (and worse than other animals with true color vision).
unsollicited-kudos t1_iuccu31 wrote
I don't think size matters that much. Cat's eyes are slightly smaller than ours and they have much better vision. Rats don't see that well, but that's mostly because their experience is more scent-based (40% of their brain is devoted to their sense of smell) so their eyesight is kind of secundary to them. Similarly, dogs can see okay but not as well as more visually oriented animals. Maybe someone else can chime in about other small animals, this is about the extent of my knowledge.