Thursday, May 7, 2009

Horses and color vision: Let's talk biology and science

Yesterday FHOTD commented in a post about flags that we don't know whether horses see in color. Actually, according to my research that is not at all true, and furthermore I don't know who would believe that we don't know something that basic in today's super-advanced scientific world.

So let's talk biology for a moment. Seeing color is not some kind of hocus pocus. It happens because we have three different types of cone cells in our eyes: cones that interpret red wavelengths, cones that interpret blue wavelengths, and cones that interpret green wavelengths. Having all three kinds of cones make us trichromatic.

Horses, on the other hand, are dichromatic, meaning they have only two of the three types of cone cells: red and blue. There's a fantastic scientific paper on dichromatic horse vision that I linked to last summer, after my horse spooked at a neon green-painted manhole cover and got me thinking about whether he could see color.

The scientific paper, first of all, explains very carefully how they determined what cones a horse has in his eyes. (I'm not a biology major, so I'll have to take their word for it. I would have assumed you'd dissect an eye and use a microscope to identify the cells inside it.) Then on page 5 they interpret their findings with a handy little color wheel that shows how horses see color. As you can see, all of the colors are fairly muted, but a small range of colors — neon green, orange, etc. — show up as varying shades of yellow. Which would explain, of course, why Panama was so startled by a neon green-painted piece of metal.

I think it's all very interesting, and of course it may have some serious implications for people who prefer brightly-colored tack and clothing — see the photograph comparisons on page 6 to see what I mean! What flight animal wouldn't consider that potentially scary?



At May 7, 2009 at 2:11 PM, Blogger jane augenstein said...

I have read somewhere that horses can see yellow and blue. I think Gilly can see those colors because of how he responds when you have a Pepsi can in your hand or the neighbor drinks beer in a blue can and he tries his darnedest to get to him for the can. (he loves beer) He also loves banana peelings? don't know why but he only wants the yellow peeling, if it has started to turn brownish, he pays no attention to it. Can he really see those colors? Don't know, he's not talking! LOL

At May 9, 2009 at 9:13 PM, Blogger Katharine Swan said...


Oh yes, I think they can definitely see colors, but the colors they see don't necessarily look just like the colors we see. If you look at the color wheels in that scientific paper, they see in shades of grey and yellow, so colors aren't as dynamic but there is more differentiation than black and white.


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