If Cats don't bother with color why do primates

The issue of whether cat can see color (more or less), brings up the question - if it’s not important to cats and most mammals to distinguish colors why is it important to primates and especially humans.

Marty Brody

I’m assuming this is in response to Are cats and dogs really color-blind? How do they know?

I am not a biologist, but I could hazard a pretty good guess.

Because cats and dogs (and their nefarious ilk) live closer to the ground, they have better senses of smell and hearing than we humans. They have never needed to develop color vision, or when they did develop it, it wasn’t a sufficiently great advantage to change Catdom As We Know It.

Think of it: you’re a cat. There is a small fuzzy thing running away from you. It smells like food. Your hearing is good enough that you can detect its location with fair accuracy. Your vision is highly attuned to sensing movement and you have the dexterity to catch your prey. Under what conditions would color vision be of more use than what you have now?

It’s not as if mice become “ripe” and should only be eaten when they change colors (as does, for instance fruit). And don’t cats generally run from predators larger than they, no matter the color?

When humans began to sit up and look across the plains, we began to rely more upon our vision to spot predators from a great distance. Discerning the difference between a zebra and a lion at 500 meters became much, much more important. Similarly, the apparent difference between a ripe apple and a green one is small—to us, that is, who have a stunted sense of smell compared to other animals. Those of us who developed the ability to discern color did very well; those who didn’t, struggled. Color vision for cats was probably a crap shoot: some developed it, some didn’t, but it wasn’t entrenched in cat behavior because it wasn’t essential. Only cats facing paper-covered jars in laboratories have faced failure because of their color perception.

That’s simply an educated Wild-Ass Guess, though.

It’s a bit misleading, and human-centric, to say that cats are colorblind. Most humans are trichromats–they have a three-dimensional color space–while cats, if I understand correctly, are dichromats (have a two-dimensional color space). It’s reasonable to wonder about such differences, but we can just as well ask why humans don’t have four- or higher-dimensional colorspaces (as I recall, it is claimed that some birds are tetrachromats; in any case such things are entirely possible). It is not as though we have in some sense maximum color discrimination and anything less needs explanation; combinations of wavelengths that are spectrally quite different can appear identical to humans. The dimensionality of the color space must be finite, and presumably there are tradeoffs to be made. Richer color discrimination presumably comes at the cost of spatial resolution, if the number of receptor cells is kept constant. There’s a chapter by Roger N. Shepard in The Adapted Mind purporting to explain why humans are trichromats, though I can’t say I buy it.