Good question. Myths about horse vision litter the ground like discarded betting stubs after the favorite loses a race. We are told that horses only see the world in black and white. They cannot see well at night. They are nearsighted. They must be shown objects from both the left and right sides because there is some weird mental wall that doesn't tell the left eye what the right eye has seen. Besides all that, it has been suggested that horses have no depth perception.
If any of this were true, some horses wouldn't object to certain colors. They wouldn't be able to graze uneven pastures at night without bumping into things. They wouldn't shy at a kite flying half a mile away. They wouldn't recognize you or their feed bucket if seen from a different direction. They wouldn't be able to jump a fence, much less a series of barriers of wildly varying heights, widths, approaches and landings. Nor could they slam on the brakes and come to an impressive sliding stop inches from an obstacle. They certainly wouldn't be able to "lock onto" and cut cattle, run barrels, or do any of the thousand of things we ask horses to do.
Since they obviously can do all these things-and do them quite well-something here does not compute.
Myths start when someone introduces a training technique based on a theory about horse vision. We try the method. It seems to work. We spread the word to friends or students. It doesn't take long for a theory to become an accepted "truth." The trouble is that while the training technique may be sound, the reasoning behind it may be off-base. When it works, people smile and nod. If it doesn't, it must be either our fault, or the horse's fault, because everyone knows horses only see a certain way.
But how do we know what another species sees, when we may not even know what other people see? Think about the astonished third grader who struggles in school until he puts on a pair of glasses and suddenly sees the blackboard clearly for the very first time.
But in fact, we are learning more about the horse's vision all the time. What we do is compare the anatomy of a horse's eye to what we know about human eyes, using some of the same instruments. We set up carefully controlled experiments to eliminate the red herrings that so easily confuse us.
"There are quite a few myths and misconceptions about how horses see," agrees Dr. Evelyn Hanggi, president of the Equine Research Foundation in Aptos, California. "After repeatedly reading and hearing odd things about equine vision, we decided to design some noninvasive studies that would provide solid evidence one way or another."
It turns out that while in some ways horses see the world very much as we do, there are a few important differences that need to be considered.