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.
A Horse's Window on the World
• Monocular vision allows a horse to see different things through each eye.
• Binocular vision allows a horse to focus on things with both eyes at the same time.
• Horses have the ability to switch between using monocular and binocular vision.
• Because of the way horses' eyes are positioned, they have small blind spots directly in front of and behind them when their heads and necks are straight.
• Allowing your horse to raise, lower or tilt his head can help him judge distances better when jumping, cutting, running or working obstacles.
• Areas of high contrast may initially startle or worry horses, but their eyes quickly adjust to differences in brightness and shadow.
• Horses do not see color the same way people do, but they are not "colorblind."
Like most open-space prey animals, the horse's eyes are placed predominantly on the sides of their heads. Quite a few studies have shown that this lets horses see nearly a full circle around them. In effect, horses receive a wide-angle, panoramic view of the world. However, horses do have a small blind spot in front of their noses, and another just behind their tails, and they probably cannot see much that is sitting low on their backs either.
What a horse sees with one eye is called "monocular" vision. And this ability to see different things out of each eye helps the horse assimilate what's going on around him in a generalized way.
Yet horses also have the ability to focus on a given object with both eyes. Using "binocular" vision, in which both eyes work together, horses can zero in on a selected point or object, such as that trail obstacle we're asking them to negotiate, or the cow we want to track.
Seeing Eye to Eye
Misunderstandings regarding monocular vision are likely behind the "just because he's seen it with his right eye doesn't mean he will recognize it with his left eye" myth. This misguided theory suggests that the two sides of the horse's brain are neither connected nor communicating. This, as Dr. Hanggi notes, would make the horse quite bizarre in the animal kingdom because, like nearly every other mammal, horses have a structure in the brain called the corpus callosum that connects both hemispheres of the brain, so information is shared back and forth.
Since just the presence of this bit of anatomy doesn't prove information actually gets transferred, Dr. Hanggi ran a series of tests using images the horses had never seen before. With no humans around to give inadvertent signals, the horses were given a choice of pictures to touch with their noses to receive food rewards.
To test the eye-to-eye myth, the Equine Research Foundation horses were trained to respond to one of two choices while one eye was blindfolded. When the blindfold was switched to the other eye, the horses had no trouble picking the correct image. These results stayed consistent through several different sets of images.
The Mailbox Mystery
So what's with shying at the same old mailbox when we come from a different direction?
This one has so many possibilities that one theory probably won't answer it completely. One thought is that sometimes horses just don't recognize objects when seen from a new angle. Dr. Hanggi did experiments on this issue and determined that horses actually can recognize rotated objects from most (but not all) orientations.
She believes the problem relates more to training than it does to vision. Horses need to be allowed to look carefully at their surroundings. Horses who have seen many objects in different situations and have developed trust in their riders generally react more calmly when confronted with just one more oddity.
Other reasons horses may shy from objects that should be familiar can range from changes in lighting, contrast and shadows, to the distinct possibility that, again, the horse may be seeing something that you do not. There could be a critter rustling in the grass, or a broken hinge that gives it a very different outline than it had an hour before.
As far as creeks, rocks, bushes, trees or the neighbor's barn are concerned, it might help to remember that just as an experienced hiker or trail rider will regularly look behind him to try to stay oriented-knowing that landmarks can be unrecognizable when seen from the opposite direction on the way home-it is possible that the horse may not recognize a potentially scary object from the opposite direction either, so he honestly needs to investigate it all over again to convince himself it's not a horse-eating monster.
If, for instance, you are crossing a creek for a second time, but from the opposite bank, for all intents and purposes, that is a different creek for the horse. If he has crossed many creeks before this, it would probably not be a big deal. But if he's just learning about navigating streambeds, give him time to check it out.
The idea that horses do not have good depth perception also seems to be based on their eyes being largely on the side of their heads. There are a number of problems with this myth.
First, viewing objects with just one eye does provide an adequate degree of depth perception. Also, remember that a horse's eyes are placed slightly to the front, giving him a 55- to 65-degree overlap. So, in addition to their monocular vision, horses have a fair degree of binocular vision (remember, two eyes working in concert). Binocular vision allows for accurate depth perception.
One way horses seem to refine their depth perception is to raise, lower and/or tilt their heads. One practical training application to this is, if you are asking your horse to jump, cut, or maneuver closely around or through something, he is going to find it a lot easier if he has a fairly loose rein and/or the freedom to move his head so he can judge distances.
Although horses do have blind spots just in front of their noses, behind their tails, and in the low areas on their backs when their heads are straight out in front of them, as Dr. Hanggi points out, "Even so, a tiny shift of the head suffices to bring these areas into view.
"In a nutshell, at any given time your horse can see an awful lot that you cannot," she added.
If your horse suddenly stops and raises or turns his head, you may not see it, but he's looking at something.
"We need to check out not only what is in front of him, but also what may be to the side or behind him," explains Dr. Hanggi. "Humans tend to have tunnel vision and concentrate only on what is in the front instead of being aware of the whole environment."
That relatively small blind spot in front of the horse's nose, however, has some major, practical implications for riders.
Shortly after Dr. Alison Harmon, of the University of Western Australia, witnessed two dressage horses collide as if they hadn't seen each other, she used an ophthalmoscope to examine the retina of a horse's eye to determine its field of vision. She found that the forward portion of a horse's sight runs approximately down his nose, with the blind spot being roughly the width of the horse's body in front of him as well as slightly above the level of his eyes.
If a horse is ridden "on the bit" with his forehead vertical to the ground, or overflexed and "behind the bit" with his nose pointed toward his chest, he only sees the dirt beneath his nose. The peripheral vision is still showing what is to the side, but he is working blind in regard to anything smack dab in front of him.
Some disciplines consider a headset in which the horse flexes at the poll and positions his face vertical to the ground, as a positive indication of the horse's softness and submissiveness to the rider. And that may be true in more ways than anyone realized. The horse might be more attentive to his rider with his head in this position, because his ability to see is limited. In effect, he has to trust his rider not to run them both into a tree.
It's a persuasive argument for riders to look up and ahead, not down at the horse's neck, since at least one member of the horse/rider combination has to see what's coming up! It might also explain why some horses are uneasy or resist being asked to comply with an unnatural headset.
An experiment was also done to determine how sharp a horse's vision might be. The horses were trained to choose between pictures of vertical black and white stripes of different widths. Researchers kept narrowing the width of the stripes until the horses showed they could no longer detect a difference. Essentially, this tested out at 20/30 vision. Perfect human vision is considered to be 20/20, so your horse could probably pass a drivers' license eye exam.
A horse's night vision probably isn't as good as an owl's, but it's probably far better than most people's. Horses' eyes seem fairly sensitive to low light, and they can see reasonably well at night. Dr. Hanggi, who is conducting experiments regarding the horse's night vision, relates a good example of this.
"I was in the high desert with ERF program director Jerry Ingersoll on our annual trip to observe wild Mustangs. One night at midnight, we were awakened by what sounded like the thunder of an oncoming train. Within a minute, a large band of Mustangs came galloping right past our tent-in the dark, through rough terrain made up of hills, gullies, rocks and sagebrush. It was an amazing experience for us and, clearly, they saw where they were going."
Also notable is that horses can adjust to major differences in brightness and shadow fairly quickly, but specific situations may affect their reactions to a great degree. The reason your horse might hesitate at entering a darkened doorway or be "looky" at a log on the trail as you are passing from a bright field into darker trees might be because he can't see right away what he's being asked to go into or over. He might need more training to develop confidence in those sorts of conditions.
While researchers are narrowing this one down, we don't seem to have all the answers yet on what horses see. Anatomy tells us that horses do have "rods and cones" ("cones" detect different colors) in their eyes. People have more cones than most animals, including horses, so although horses certainly do seem to be able to detect some colors, they are probably "colorblind" in the sense that they may not see as many colors as we do. Dr. Hanggi's recent, soon-to-be-published experiments, strongly indicate that horses have red/green deficiencies.
Even so, in an experiment designed to disprove a theory that tried to explain a particularly nasty wreck, Dr. Hanggi showed that horses certainly can, for instance, detect green objects in front of green backgrounds. She explains, "Even though horses may not see colors as humans do, they are still capable of seeing the objects themselves. Color vision deficiencies do not make objects invisible."
So, at the end of the day, the one question that cannot entirely be answered by science is "How do our horses see us?" Are we friends? Foes? Leaders? Subordinates? Predators? Partners? Are we someone who puts them in constant danger, or are we someone who can be trusted?
Those wonderful eyes don't just reflect images. They also reflect how much we have learned and how we treat our horses. They reflect us.