A horse's world is colorful, too

Madison, Wis.-

Two out of three isn't bad.

A recent study, reported in TheHorse.com, indicates that horses do possess color vision, even if it is a much more limited version than their human friends. At least two different classes of cone cells are necessary for color, and two of these classes are located in a horse's eyes, as opposed to three classes in humans, according to researchers at the Medical College of Wisconsin and the University of Wisconsin-Madison's Schools of Medicine and Veterinary Medicine.

The cone cells responsible for color are spread out in a thin layer at the back of the eye.

One cone class in the horse absorbs light maximally in the short wavelengths (blue light), and one absorbs light in the middle to long wavelengths (green to red colors). The latter cone class differs from human eye cones. Humans typically have three (trichromatic) cone cell types. Horses have dichromatic color vision, although it was originally believed they were colorblind.

To determine whether horses were dichromatic, scientists used a non-invasive procedure to probe the electrical response of the cone cells to wavelengths of light in the equine retina. A computer algorithm then calculated how each color in a digital photograph would appear to a horse.

Results of the study were reported in the Journal of Vision.