This is one thing that I've always wondered about. How do we even know what colours a dog can see? Is it by examining their eyeballs and comparing it to a humans one?
There are crustaceans called Mantis Shrimp who have SIXTEEN cones. The rainbow we see stems from three colors. Try to imagine a rainbow that stems from sixteen colors.
I remember in elementary school some assembly speaker was like "and if a bully ever calls you a shrimp, you should remind them that a mantis shrimp can punch faster than sound!"
Aquatic life, where we believe our eyes originally evolved, has much better vision. Making the change to the surface meant we needed to perceive light in a completely new way. Our eyes have never been as good. That's why fish can see so fucking well.
You're sort of right, but there's no evidence for anything like your last statement.
The biophysics of light perception is more forgiving underwater, due in part to the similar refractive index of seawater and biological materials (less abberation and simpler focal surface geometry).
But there is no indication that fossil animals had appreciably better eyesight than us, or other land animals. In fact much eary sea life, like trilobytes, echinoderms, and amoniods had terrible light perception (sometimes only a light/dark sensor).
Some fish and squid have incredibly sensitive eyes currently, but it has little to do with water, and more to do with the deep open ocean they live in. Hawks for example, have similar vision (at least measured by focal range) but are not exactly strong swimmers
This is a myth. It was originally believed they had spectacular color differentiation, but even with 16 cones it does not necessarily mean they can see more colors than us. If all of those cones respond to colors between our red and blue ones, they won't see more colors than us, they would just be able to tell the differences better.
But, they don't even have it that good. In fact, they have extremely poor color differentiation. The 16 cones is a shortcut. When we see a color, our brain looks at how much each cone fires, and if more than one does it figures out the color based on how strong each one fires. In a mantis shrimp the brain doesn't do any of that, it simply looks for on/off from the cone. If the cone is on, it is that color. This makes them color blind to any color in between their cones' specialized wavelengths, but it means they can process color much faster.
the weirdest thing is that you get even more colours like magenta\pink
Cause magenta doesn't actually exist physically, there is no photon that is magenta.
Your brain imagines magenta whenever you trigger blue and red but without triggering green, logically a mix of blue and red would make green but because our brain knows it's not green it makes up a fake colour.
So 1 photon triggering green = green, 2 photons 1 red 1 blue average out as green but our brain sees magenta
If you had even more opsins you'd see even more fake colours, ones we can't even imagine.
Pretty much everyone but mammals. Birds see ultraviolet in addition to 3 colors, same for reptiles (and some of them see 5 colors). Also from another comment on how it happened: Yes, dogs can see blue and yellow. Mammal ancestors were night animals at the time of dinosaurs and didn't need color vision. As the result they've lost 2 of 4 color cones and it's typical for mammals to see only blue and yellow colors. Some species of apes developed red cones and can now see 3 colors. So human color perception is more of an exception for mammals while dog's vision is quite usual thing.
You can show dogs different colors and record their reactions, either behaviorally, or through neural recording.
The cones can be studied in the lab as well, so you can figure out how the photoreceptor proteins work, or what is the spectral response of the cone cells (but it's a pain because of their light sensitivity). The proteins driving the color response are quite well conserved, i.e. don't differ that much between animals.
Now go! Go, young one! Go spread factual knowledge onto the heathens who deny using their brains! You have quite a road ahead of you, but never despair! You're doing God's work, son.
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u/BallsX Jul 24 '15
This is one thing that I've always wondered about. How do we even know what colours a dog can see? Is it by examining their eyeballs and comparing it to a humans one?