How horses see the world - The Horse Owner's Resource

How horses see the world

Many common problems between horses and their handlers are rooted in how differently they see the world. Here’s what you need to know about equine depth perception, night vision and other sight-related systems.
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The barn hose sits in the same place every day. When it’s moved a few inches, no one notices … except the horses. Some only cock an ear toward the change; others go goggle-eyed and giraffe-necked as they scoot past with bellies arched sideways. Annoying, isn’t it? They’ve seen that hose a million times.

riding in ring

By nature, equestrians ride and train on human assumptions, imagining---if we ponder it at all---that the horse visualizes sights the same way we do. The reality is quite different, and by recognizing the unique ways in which horses see and interpret the world, we can address many common problems between horses and their handlers. Along the way, we’ll figure out why that hose is such an issue.

NIGHT VISION: SURPRISINGLY SLOW ADAPTATION

We’ve all heard that horses can see in the dark, so they have no trouble jumping at dusk or loading onto the trailer at dawn. But take a look at your horse’s pupil sometime. See how much longer and larger it is than a human pupil? Large, horizontal pupils take in more light across a wider range of visual angle. Having entered the eye, that luminosity filters toward the retina, a patch of cells that changes particles of light into neural impulses. Those impulses are then routed to areas of the brain that interpret their meaning.

Horses also have iridescent collagen fibers in an upper area of the eyeball called the tapetum. These fibers reflect light from the ground into the eyeball, allowing the horse to see as he moves in darkness. Human eyes have a similar mechanism, the choroid coat, but it is not as large or strong as the tapetum and cannot reflect light to an equivalent degree. In both species, these fibers become visible when reflected in a camera flash or headlight. In horses, the eye-shine varies among green, yellow or blue depending on a horse���s color and age.

With large pupils and a reflective tapetum, horses have pretty good night vision---enough to wander from hay bin to water trough in the dark and notice movements in the shrubs. A horse’s night vision is more acute than a person’s, but it’s still not sharp enough to discern details, hop crosspoles or load into trailers comfortably.

Then there’s the real rub: It takes a horse’s eyes much longer than a person’s to adapt to dark conditions. Human eyes require about 25 minutes to adjust from bright sunlight to darkness. Equine eyes need 45 minutes, almost twice as long. So, upon entering a dim building from daylight, your horse will be blinded by darkness long after your eyes have adapted. After adaptation, a horse’s vision is 25,000 times more sensitive than before. Unfortunately, your 45-minute training session is about done by then.

Show horses are often required to move from sunlight into an indoor arena to perform. Top facilities use intense lights for illumination, but smaller venues often don’t. Although all disciplines are affected, jumping is especially so because it is so dependent on acute equine eyesight. Jumpers have to judge the height and width of fences very quickly, scanning distances on a short approach, adjusting stride length for takeoff, carrying riders who transmit countless cues and coordinating their bodies to clear obstacles by only an inch or two. These feats require precision that would humble many human athletes.

Riders all over the world warm up hunters and jumpers in bright sun prior to competition. After a typical warm-up, Blaze’s pupils are constricted to the maximum degree, admitting as little light as possible. Retinal chemicals that transduce light into neural impulses are at their ebb. This combination of pupillary contraction and chemical paucity allows the horse to jump in bright sun. High elevation, central latitudes, low humidity, pale arena sand and white fences demand even greater accommodation.

Blaze is jumping well in warm-up when the gate steward calls his number. His rider removes her sunglasses at the in-gate, instantly improving her indoor vision. Too bad her mount can’t shove his face into some military night goggles. Through the gate they go, galloping into the murk to leap over eight or 12 jumps that the horse can barely see. And oh, by the way, like all of us, Blaze’s rider expects top-notch performance. But he hasn’t come close to the 45 minutes he needs to accommodate to indoor lighting.

The scenario described here is common. We allow it because we are not aware of the visual hardship for the horse. Most of us reprove mounts who balk at the in-gate, weave between fences, skirt the flower box or refuse to jump. We assume that if we can see the course, they can, too. But imagine moving from a sunny parking lot into a darkened movie theater, then dashing around under a heavy backpack---hurdling seats, slipping on buttered popcorn and dodging angry patrons. The fact that horses try to perform under such circumstances is a testament to their generosity.

Like people, horses differ in individual visual abilities. One horse might require a little less than 45 minutes to adapt to dim light; another will require even more. Age plays a role, too. Older horses with healthy eyes take in less light than younger horses do. This age difference occurs in people as well---in fact, the average person’s eyes take in 66 percent less light at age 60 than at age 20. No wonder the world seems a little gloomier as we get old.

What can you do to help your horse’s eyes adapt before performing? There’s no perfect solution, but some measures will help. Allow him to walk in the shade before entering an indoor arena. Stand at the gate for a few minutes while the preceding pair competes. When possible, schedule a jumping performance right after a flat class, giving your horse 15 minutes of adaptation time prior to starting over fences. Remember that a jumping round, no matter how easy it looks, is a complicated and unnatural coup for a horse. He can’t just phone it in.

For the longer term, urge show organizers and facilities managers to brighten indoor arenas with strong artificial lighting. Exhibitors, trainers, boarders and owners have the power to make such requests as a group, especially when safety is at stake. Suggest that officials cordon off a small strip of the indoor as a wait-and-walk area for horses about to perform. Ask that they open doors to illuminate the area inside. When all else fails, scratch. Your horse’s long-term welfare, as well as your own, are more important than three minutes spent hopping around in Aladdin’s cave.

Horses need to see their surroundings, whether leaping seven-foot walls or just chillin’ in the barn. Those who can’t see well compensate by using other senses to a greater degree. This can yield new kerfuffles, as when the horse begins to listen to a dark indoor arena so closely that he spooks at the sound of two air molecules colliding. Equus caballus is built with a great visual system for a reason---he needs to see!

DEPTH PERCEPTION: LIMITED BUT VITAL

Eyes perceive physical views, but it takes a brain to compute visual distance. A person takes in two views of a given scene, one from each eye. To see this for yourself, hold your finger in front of your nose at arm’s length. Close one eye and line your finger up with something vertical in the distance---a door frame or a fence post, whatever. Now open that eye and close the other. Your finger will appear to jump back and forth as you alternate eyes. Those are the two views that your right and left eyes send to your brain. The brain computes the difference between them, and as if by magic, you become aware of depth. Using this automatic computation, you can look at a field of horses and note that the cute sorrel is farther from you than the pretty bay.

Human depth perception is extremely precise because our eyes are so close together. They are also yoked, moving in concert with each other for precise tracking. With this design, the average person can distinguish one-eighth of an inch in disparity from a distance of 16 and a half feet. In other words, if you were standing one long stride away from the takeoff to a double-rail vertical, your brain would tell you whether one of the rails was set an eighth-inch behind the other one.

A horse’s eyes are set far apart, so his ability to see depth is limited. From most angles, horses cannot get a left-eye and right-eye view of the same object in one glance. People can see an outstretched finger with both eyes simultaneously. But Blaze can’t. As a prey animal, he’s built for peripheral motion detection at the expense of depth perception.

For horses in dressage, reining or pleasure, depth perception is not so critical. But consider cutting, barrel racing or jumping. The horse needs to know how far away relevant objects are and the speed with which those distances are changing as she moves. A horse can improve depth perception slightly by raising her head or lifting her nose, but this often complicates her task. In cutting, for instance, the horse needs to keep her eyes down on the cow and her head low to make quick turns. In jumping, she needs impulsion from her hindquarters to power off the ground and abdominal tuck to lift her legs. The physics of such movements require that the horse maintains a round back for core strength, which often precludes the high-headed position that aids depth perception.

The distinction between hunters and jumpers is also important. Top jumpers---judged by the size of obstacles and the speed of their rounds---are often selected because their necks are set high on the withers, with head position proportionately higher. Those without that conformation are often trained to approach jumps with their heads raised. If you watch a jumper approaching a fence, you will see her head lift in the last stride or two. This natural form provides both eyes with a brief view of the jump, so that the equine brain can determine its height and width. But the view is fleeting---fractions of a second---and it’s late. 

Depth perception is easier for hunters. These horses are judged on the quiet beauty of their jumping form and are taught to maintain a long frame with hindquarters engaged, necks arched long, heads low and faces near vertical to form a strong topline. This position can be preserved over fences because hunters are given a long approach with which to see jumps without raising their heads much. Good hunter riders encourage horses to look at a fence while rounding a distant corner. This supplies the horse with a better side view, a longer front view and more time for the brain to compute distance to the jump.

VISUAL CAPTURE: COMPENSATING WITH OTHER SENSES

Vision is our strongest sense---it hogs more neural real estate than any other sensory system does, filling almost one-third of the human brain. With such clout, it can override other senses under the right circumstances, a neural ability known as visual capture.

Visual capture is responsible for the fact that ventriloquists can fool us. We believe that speech is emanating from a dummy’s mouth, even when the human speaker is standing before us. The visual movement of the fake mouth captures our attention and links it to the spoken words. Magicians use visual capture to hide actions of their hands in plain sight. Moviegoers gesture toward an actor’s mouth on the screen when asked where the sound is coming from---even when theater speakers are placed at the back or sides of the house.

Because we rely so heavily on sight, it’s natural to suppose horses do, too. But a horse’s acuity, depth perception and visual content identification is much worse than yours. He compensates for his visual weaknesses with excellent hearing and a fantastic sense of smell. We help horses by letting them rely on these stronger senses. The next time your horse skitters away from a safe spot, think about what he might hear or smell that is imperceptible to you. His world is not all about vision.

CATEGORICAL PERCEPTION: MAKING SENSE OF THE WORLD

Once past the eye and through the sieve of depth perception and visual capture, our brains interpret sights to identify what we see. Human brains operate on the basis of categorical perception---the natural tendency to organize sights and sounds into meaningful groups.

Let’s suppose you see 10 Quarter Horses and 10 Thoroughbreds scatter-ed around together in a pasture. Even if you are not familiar with these breeds, your brain will automatically sort the horses according to their physical features. The tall lean endurance athletes will go into one group, and the ripped little muscle guys will go into the other group. Your brain is categorizing the horses without your awareness or approval.

Categorical perception represents similarity across members of a group more easily than differences among individuals within that group. The downside of human categorical perception is stereotyping; our brains are designed to sort rapidly according to external traits. The upside is speed---we categorize instantly without thinking.

With effort, we can stave off the brain’s tendency toward categorical perception temporarily. Think of the physical view of each of the 10 Thoroughbreds. They’ll differ somewhat in height, weight, conformation, nervousness and activity level---features that our brains won’t calculate at first. But categorical perception also blinds us to radically different views of each horse. The physical sight of Thoroughbred Number Three viewed head-on looks nothing like the one we get from his back or side. He’s dark bay, but when caked in dried mud after a good gallop, he looks like a buckskin. If he suddenly lifts a hind leg and scratches his face, we are not fooled by our eyes’ view into thinking he is a different horse. Categorical perception is so good that it’s hard for us Homo sapiens to even imagine that each view of the same horse could represent an entirely new animal.

Horses aren’t capable of much categorical perception. And that’s why horses notice minor discrepancies in the position of the barn hose. A different view, or the disparate position, of a familiar object is almost the equivalent of a new object. Our neural networks are firing simply for “hose” when we see one. We take a glance, and yep, it’s a hose. Our horses’ neural networks are firing “new hose,” “faded hose,” “muddy hose,” “green hose,” “black hose,” “hose wound in 24-inch loops,” “hose wound in 14-inch loops,” “hose stored by sloppy human” or “hose stored by OCD human.” Every perception is separated. The horse relies more on his eyes than his brain for visual identification. The same noncategorical effect occurs with sounds, touches, smells and tastes.

A horse who is exposed to the same jumbled scene daily will become accustomed to it. But our eyes often assume that the jumble never changes, when in fact it does. Occasionally, I use a round pen located next to an area where frequently handled ranch equipment is stored. Horses who have used that round pen for years still skirt the jumble because the position of the equipment is changed slightly on almost a daily basis. Noncategorical equine brains are designed to notice these tiny changes; categorical human brains are not.

Training and trust help horses to ignore their lack of categorical perception just as humans can learn to override stereotypes. But always remember that equine and human brains are working against their respective natures. When people are tired, distressed or pumped up with adrenaline, their brains revert to stereotyping behavior. And when horses are pressed into difficult situations or lose patience with handlers who do not understand them, their brains will direct them to whirl and bolt from familiar objects. That’s just the nature of each beast.

It’s annoying when a horse gets all jacked up about the same hose she’s passed a million times. A small change in its position barely registers on our categorical brains. But to her, that change represents the possibility that a known object has become a threat. From an evolutionary perspective, shying at new sights is a smart way for a horse to stay alive.

Understanding the variance between equine and human vision helps us to train horses more effectively. It allows us to increase and assess the horse’s degree of trust---is he willing to rely on our leadership when faced with intimidating new sights? It lets us calm our horses while they perform, which in turn allows them---and us---to do a better job. It improves communication between horse and handler. So, next time that hose rears up in front of your sweet mare with an ugly leer, understand why she notices it so much more strongly than you do. Learn to see the world through her eyes. You’ll enjoy the view.

About the author: Janet L. Jones earned her PhD in cognitive science, the study of the human mind and brain. She won UCLA’s dissertation award for her research on brain processes. Now professor emerita, she has taught the psychology and neuroscience of memory, language, perception and thought for 23 years and is the author of three books. Jones began riding at age 7. She has competed in Western, English, reining, halter, hunter and jumper classes throughout the West and uses the principles of dressage with every horse. Jones currently owns a 17.1 hand off-the-track Thoroughbred who makes every day interesting. Readers can reach her at ridewithyourbrain@gmail.com

This article first appeared in EQUUS issue #462, March 2016.

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