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Chapter Three

How Horses See

See that sliver of light on the sand, shining through a gap in the roof of the indoor arena? Every time she goes past, Hawkeye arches her neck and skirts the boundary as if it’s a rattlesnake. The sliver changes in size and shape with the sun’s movement, and the horse seems to see each tiny difference as a brand new snake. When a concurrent sound erupts—oh say, the sound of a grain of sand shifting—she leaps sideways.

These are normal behaviors caused by the way a horse’s visual system is hard-wired into his brain. We can teach the horse to overcome some of them, but we can’t force such behaviors away. Nor can we make a horse see the way we do. How we respond to our mounts depends largely on human vision, and it biases our expectations of what horses see.

When we ponder equine vision, we know it must differ from our own; but when we’re busy handling a horse, that fact is easy to forget. Equine vision is fuzzy—contrary to our assumptions, horses cannot make out details or see strong edges. They have trouble focusing on objects, especially those that are near to them. We can’t see the periphery of the world, but it’s the equivalent of front and center for horses—they get a complete double-side view that we never see. They’re also tuned to identify tiny flicks of motion that the human eye misses. And objects can fall into many equine blind spots, becoming invisible until they suddenly pop up like trick-or-treaters saying, “Boo!”

Eye and Brain

We construct sight using information from our eyes combined with knowledge in our brains. Things can go wrong at either end—the eye or the brain. People whose eyes become blind still see images and dreams. Those whose visual cortex is damaged, but whose eyes are intact, often see lights and shadows but can’t make sense of them. In rare cases, people who are completely brain-blind can navigate around invisible objects or reach accurately to grasp coffee cups they cannot see. This ability, called blindsight, isn’t limited to humans—cortically blind animals can do it, too.

Rarely, a snippet of visual cortex is impaired so specifically that its owner—having otherwise normal sight—suddenly cannot see color, shape, or perhaps movement. Imagine trying to cross a busy street with your intact eyes open when your brain can’t perceive motion. Cars travelling 50 miles an hour become a series of still images stopped along the road. A moment later, they’re stopped in different locations.

Neuroscientist Gerald Edelman said it best: “Every act of perception is, to some degree, an act of creation.” The trouble for a horse-and-human team is that equine brains create perceptions in ways that are very different from ours. Visual information travels from the eye to the brain in both species, of course. But the human brain sends back six times more neural information in the opposite direction, from the brain to the eye. This wiring boosts perceptual interpretation: lots of knowledge is melded with the human eye’s pictures of the outside world. So, who’s more objective in seeing reality, you or your horse? Hate to break the news, but it’s probably your horse. Equine brains should be less prone to illusions than human brains are.

Visual Acuity

Horses often give the impression of superb eyesight. Walking in an open field, a bird flicks a wing and they’ll raise their heads, point their ears, quiver their nostrils, and widen their eyes with what seems to be intense focus on the bird’s location. Some trainers refer to this as the look of an eagle, and it is indeed an impressive display of intelligence and sensitivity. However, the reason for it depends less on good vision than bad vision. Horses try to improve blurry views by raising their heads and enlarging their eyes. Their ears perk up to listen because they can’t see stationary details well. Their nostrils expand to optimize an excellent sense of smell.

Equine eyes are eight times larger than human eyes, larger than those of any other land mammal. But a horse’s acuity is considerably worse than ours. Acuity refers to the ability to make tiny discriminations in detail while focusing on something in the center of the visual field. Reading is a great example for humans—right now, your eyes are picking up tiny differences in the black marks on a page. You can see the difference between an “e” and a “c,” for example. The distinction is meaningful—witness the confusion if you misread that you have “cars” on both sides of your head.

By convention, normal human acuity is 20/20. What a person with normal vision can see from a distance of 20 feet is the same as what you see from a distance of 20 feet—if you have normal vision. But normal equine acuity ranges from 20/30 to 20/60.

Let’s consider the visually gifted (20/30) horse first. Details you can see from 30 feet away, a sharp-eyed horse can only see from 20 feet away. In other words, he has to be 50% closer to see the same details—he has half your acuity. What if your sweetie-pie is near the low end of normal equine acuity at 20/60? Details you make out from 60 feet away, he cannot see until approaching within 20 feet. That’s a 200% impairment compared to human vision!

Even the 50% deficiency is enough for any rider to consider. Imagine what a horse sees when the two of you approach a jump (figs. 3.1 A & B). For you, it’s clear, sharp, and bright. You’d be mighty nervous if it looked fuzzy and faded. But equestrians are often startled to see photographs constructed to show what a jump looks like to a horse. Even in sunshine, the horse’s view of a jump is blurry, hazy, dim, flat, vague—all the adjectives you’d rather not deliberate as you’re galloping 30 feet per second to a big oxer that could break your neck.

Beyond the normal range from 20/30 to 20/60, horses differ in individual acuity just as people do. Twenty-three percent of horses are near-sighted (they do not see details clearly until they get much closer than equine normal to an object). Forty-three percent of horses are far-sighted (able to see more clearly only as they get farther away). It stands to reason that slightly far-sighted horses excel in disciplines like jumping because the ability to drill down on fine points from a distance fuels their athleticism.

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3.1 A The rider sees a jump clearly on approach.

3.1 B The horse’s brain sees the same oncoming jump with less acuity and poorer focus.

Acuity for objects close to us worsens with age because the natural lens inside human and equine eyes hardens over time. If you’re over 50, you know what I’m talking about. The best acuity in horses occurs around age seven. Prior to that it’s not fully developed, and afterward it begins to decay. Breed makes a difference, too. Horses with long convex faces, like Standardbreds and Thoroughbreds, have better acuity than horses with short concave faces, like Arabians.

Focus

The human eye is superb at focusing on one detail of a scene. Muscles holding the flexible lens of the eye pull it into a more convex shape to focus on objects close up. You can feel these muscles working if you hold a finger up in front of your eyes. Focus on the finger then look past it (without moving your eyes) to a distant object. Go back and forth, getting the feel of the ciliary muscles that flex your lens. This ability—called accommodation—allows us to inspect objects while working on them with our hands. Humans excel at visual accommodation.

Horses do not. Their ciliary muscles are too weak to pull the lens into a more convex shape for greater focus (fig. 3.2). So when you hold something near your horse’s face—a bridle or clippers—he can smell it but will have great trouble focusing his eyes on it. To show your horse something new, hold it near his nose for a good sniff or on his shoulder where he can feel it with his excellent sense of touch. If it must be seen, hold it out in the air several feet away, and wait a bit. What little focus horses can achieve happens slowly. That’s why sudden movements near their bodies can surprise them.

3.2 Like the human eye, the equine eye contains a pupil, iris, ciliary muscle, and lens. However, it is a bit more compressed, or flatter, in shape than the human eyeball.

Range of Vision

Ask a child to describe a horse’s eyes. One of the first things the child will mention is that they are very large and set on the sides of the head, unlike small human eyes that point forward. This simple observation generates profound differences in the ways humans and horses see. Eye position affects visual range, peripheral motion detection, and depth perception. Equine eyes can even move independently to scan one side of the world more intently than the other.

Human sight is accurate enough to decode tiny marks on a page, but only for a very small slice of the view. While reading, a few words in your central vision are truly clear; the rest are blurred. Stretch your arm out to the side, holding something like a pencil vertically in your hand. Look straight ahead. You won’t see the pencil in this position. You can’t even see your arm. Now move your arm slowly in a wide outstretched semi-circle toward the front, keeping your eyes focused on a distant point in front of you. No cheating! The pencil remains invisible until it reaches almost a 45-degree angle. Human vision is limited to roughly 45 degrees on either side of our noses, for a total of about 90 degrees (figs. 3.3 A & B).

By contrast, if we held a pencil straight out from the side of a horse’s head, it would be almost in the center of his vision. With eyes on the sides of his head, he catches a 340-degree view, almost four times greater than the range we see. Imagine what would happen if we humans had four times more vision to process every second of the day. We’d be edgy, too!

The horse’s visual range stretches from the outside of the nose all the way around to an imaginary line extending back from the hip. The last few degrees of angle near the hind legs and hips permit only very poor vision. When leading or riding your horse, the vehicle that you cannot see approaching from behind your shoulder is within his line of sight, but it’s not too clear. It’s coming toward him, often at a rate faster than he is moving. Green horses see this as a chase, and every fiber of their being says that the way to survive a chase is to run. Now!

3.3 A Human range of view is about 90 degrees, so the rider in this drawing only sees someone moving hay near a wheelbarrow.

3.3 B Equine range of view is about 340 degrees, so the horse sees everything except the bird behind him.

Working with the Side View

One of the most common mistakes made with nervous horses is to thwart their side view. Humans can’t see it, so we forget it’s there. We lead horses through narrow passages forgetting that the walls completely block their primary lines of sight—then we wonder why the horse is skittish.

Because it’s best for our forward-facing eyes, humans assume that the frontal view is also best for the horse. Some equestrian websites even advise this position. Let’s return to Hawkeye, a lovely appendix hunter shown by an excellent equitation student who was new to me. We were working in the indoor arena when Hawkeye skirted the sliver of light that I told you about. At first, I just watched.

The rider was annoyed. In keeping with standard technique, she pushed Hawkeye straight toward the sliver of light on the sand that already scared the bejeebers out of her. She tried to make Hawkeye stand still and stare at the sliver head on, eyes bugged out like tennis balls. The horse danced back and forth, trying to turn to the side, and each time the rider cued her back to center. These demands—which good riders carry out every day—provide a perfect example of riding against the equine brain.

How so? Well, let’s think it through.

 From the front, human eyes can see an object clearly, but a horse’s wide-set eyes cannot. All Hawkeye knows is that her rider is upset, forcing her forward to a place she considers a threat.

 Without radically moving their heads, horses can’t see much below the level of their eyes, and they see nothing under their noses. So, as Hawkeye reluctantly approaches the light-snake, it vanishes from her line of sight. This makes it all the more frightening.

 Standing still concentrates a horse’s fear rather than alleviating it. Frightened horses need to move; that’s what their brains are telling them to do.

 Each time Hawkeye cocks her head and pivots to the side for a better view, her rider pulls on one rein and presses with the opposite leg, pushing her back to the frontal stance where equine vision is worst.

We might scoff at a big horse who is afraid of a sliver of sunlight or an evil paper cup—but fear is in the eye of the beholder. When was the last time you felt good about a big hairy tarantula running through your hair?

Hawkeye refused to obey the frontal commands, and by now the rider was very frustrated. At such moments, it’s tempting to dismount and drive to the nearest ice cream store for solace. But that only teaches a horse that shying buys her a nice safe stall for some couch time. Because the horse was afraid but not terrified of the light-snake, I asked the rider to remain mounted and distract the horse with a task that moved her away from the threat. Yes, this sounds like “letting her get away with it,” but work with me for a minute here.

The best technique is to ride to any distance the horse considers safe, with the object in view (fig. 3.4). Trot back and forth in a series of loops that place the object most frequently at the horse’s side. Focus on pace, relaxation, and inward bend; ignore whatever’s scary—don’t even glance at it. When the horse settles at that distance, gradually enlarge the loops, maintaining the distance that keeps him tranquil. Ride a foot or so closer to the object each time you go by. When the horse passes it calmly, even from a distance, stroke his neck and speak kindly but keep moving. We want the horse to believe that the task is to form loops with an inward bend—period. If he skirts the fright-sight at some point, decrease the loop to make the task easier. Move closer when the horse is ready, not when you are ready.

3.4 When the horse is frightened of something, like a sliver of light on arena sand, avoid a frontal approach. Instead, work gradually back and forth from the sides with a distracting task until the horse settles. This method accommodates equine vision instead of expecting the horse to adopt human frontal vision.

A simple lesson like this might take 1 minute or 100, two days or two months. Don’t push or punish fear. If the horse needs a 50-foot berth to negotiate an object calmly, give it to him. The priority is mental composure, not physical distance. Tomorrow you can set the goal for composure at 45 feet. If you’re rushed (“I’ve got an appointment!”) or you’re annoyed (“You’ve seen that thing a million times!”), start the lesson another day. Forcing horses is a good way to destroy their trust in you, frighten them all the more, and wake up with Nurse Ratched beside your bed.

Within 10 minutes of this exercise, Hawkeye was walking, trotting, and cantering past the light sliver without looking at or bending away from it. She was relaxed and calm, with no struggle between horse and rider. But it’s not always that easy.

My Horse Is Still Scared

Suppose you try this exercise, but your little knucklehead is still freaking out. Here you revert to groundwork. Ride to a spot he considers relatively safe. Dismount and immediately put him to work. If necessary, longe him to get his mind off the problem. Test his progress by gradually moving the longeing circle so that the fright-sight is closer to the horse’s side.

Now slow to a walk, remove the longe line, and try leading the horse in the same loops you used before, at the closest distance he considers safe. Give him a chance to discover that the patch does not bite. If necessary, use some vicarious learning: Let him watch a familiar human friend walk to the object, stand next to it, and speak calmly. Stroke his neck and encourage him to approach from the side. A step or two more than the horse wants equals success. Offer praise and stop for today.

If the horse is so deep into his fraidy-hole that this technique fails, have your friend bring a known, preferably dominant horse to the object the next day. (Verify ahead of time that this horse is unafraid.) Speak slowly and stroke your horse’s neck while he watches his buddy survive the terror. If this also fails, move out of sight of the object and put your horse to work on a completely unrelated task. Tomorrow, start building his trust using objects that he considers less frightening. Eventually, he will be calm enough to return to the original fright-sight and try again.

When your horse is finally relaxed enough to advance face-first, let him stretch down and forward for a good sniff. He’ll probably startle a couple of times—that’s okay, you’d jump too if you had to sniff a tarantula in your blind spot. Touch the hazard so your hand makes a soft noise against it; this will allow the horse to learn more through his ears. Gently roll or push the object around as the horse becomes accustomed. It’s important to wait for this frontal approach until the horse is completely relaxed while approaching from the side and standing next to the object.

Peripheral Motion

The back of an eye—horse or human—contains 55 different types of cells specialized for vision. But relax, we only need to discuss two: rods and cones. Stop reading for a minute and look at a scene. Anything: your living room, a view out the window, your hand, whatever. Every pixel of light or dark that you see in that scene is transmitted through your rods and cones. Each cell corresponds to a tiny part of the visual scene, and if that part of the scene is bright, its rod or cone sends a signal to your brain. If another minute piece of the scene is dark, the rod or cone corresponding to it stays mum. Every part of the visual scene is coded by 210 million rods and cones in the human eye, until your brain contains a neural pattern of light and dark that represents the entire view. Every time you move your eyes, your rods and cones transmit a new set of signals. Pretty cool, huh?

Rods are especially good at picking up off-center motion in poor light. They do not transmit detail. Equine eyes are loaded with rods, and rods are connected to cells that send information about motion on a fast track to the brain. This combination gives horses an extraordinary ability to notice tiny rapid movements. If we had a horse’s rods, we’d shy all the time at the countless zips of motion flying through our view. Riders often complain that their horses are “shying at nothing”—in fact, they are shying at very real sights that we have too few rods to sense. What’s truly remarkable is that horses don’t shy more and that they allow us to modify the behavior at all.

So, rods and cones transmit a scene’s pattern of light and dark to the brain. The human brain then takes half a second to process each glance at the world and determine what it has seen—shape, color, size, distance, meaning, importance, and so on. Half a second of processing is out of the question for a horse in the wild: He needs to notice the faintest wave of the grasses and step on the gas. If the movement turns out to be a bicycle instead of a lion, that’s okay. Little is lost by running from a bicycle.

By nature, the horse relies on peripheral motion vision for safety. It dictates his need to startle or bolt—and otherwise “misbehave”—while ridden. Help him out by sharpening your own peripheral senses. Try to become more aware of objects behind and to the sides of your eye, putting your ears, nose, and knowledge to work. Begin to notice with your body where your horse is looking—it’s an intuitive skill that develops with attention and practice. If horses are all jacked up in an area where they’re normally calm, investigate. Chances are good that they notice something you do not and are trying to tell you about it.

Blind Spots

Despite its horizontal band of panoramic vision, equine eyesight includes a number of blind spots. Without changing position, the horse cannot see above his neck or back, beneath his belly or neck, or directly behind him. The sharp acuity needed to inspect or identify objects is best in a horizontal streak at the horse’s eye level, due to the distribution of rods and cones in the eye. So nearby dogs or children on the ground, or balloons and birds above eye level, are hard for the horse to spot until they move.

The area to the outer sides of the horse’s back legs is only barely seen. Surprised from behind, even the sweetest horse can kick in any direction, causing severe harm or death. That’s why we approach a horse’s hindquarters from the shoulder, moving back while speaking, standing close, and touching his side. Lesson number one to new riders is never to walk up behind a horse.

Another blind spot exists in front of the horse’s face, from eye level to the ground below his nose and out to about six feet. A hand suddenly raised in this area appears to come from nowhere. Horses cannot see the grass they eat, the bit they accept, the fingers that stroke their muzzles, or the ill-supervised child who stretches up to kiss their soft noses. Instead, they use their long mouth whiskers to sense this area. A horse whose whiskers are shaved is at a sensory disadvantage.

Finally, there’s a blind spot inside the equine eye that projects onto the visual scene when horses move. All those cells at the back of the eye transmit their signals along the optic nerve to the brain. To carry them, the optic nerve has to connect to each eye, and where it connects, rods and cones cannot exist. This location is called the optic disk (fig. 3.5). It occludes sensory receptors just like a manhole cover hides the drain below a street.

3.5 The optic nerve creates an internal blind spot where it exits the human and equine eye. Cells at the optic disk cannot sense visual information from that part of a scene.

When the head and eyes remain still, the visual area of the world that corresponds to the optic disk becomes invisible. This is true for people and horses—although the equine optic disk and its corresponding blind spot are larger than ours. In daily life, we move our heads and eyes around to solve this problem. Human brains also fill in the blind spot by imagining objects that must be there even though our eyes can’t see them.

If you find the blind spot in your eye, it will be easier to understand the blind spot in your horse’s eye. Take a look at figure 3.6. Hold the book up so that the cross is in front of your left eye. Close your right eye and stare at the cross with your left eye. Without moving your left eye, begin to notice the outer periphery of your vision so that the black circle is visible. Now move the book in and out slowly—closer and farther from you. When the book is 4 to 12 inches from your left eye, the circle will disappear. That’s your blind spot! When you find it, make tiny movements with the book so the circle falls into and out of the blind spot. It will vanish then reappear.

3.6 Find your blind spot. (Please see text for instructions.)

You can play games with your blind spot. Don’t tell anybody, but in boring academic meetings, I used to focus my eye just to the side of where a trying colleague was seated. Then with imperceptible movements, it was possible to move the person’s face into and out of my blind spot for some private entertainment. You can learn to do the same. Stand far enough back at a horse show, and you can even make a naughty pony disappear.

More importantly for our purposes, your horse has a roaming blind spot large enough that an object can disappear at the right distance. This object could be a bird, dog, or small child, for example. If we step silently out of a horse’s blind spot, or even if we remain stationary but the horse moves, we might startle him. Sudden discoveries make horses nervous—no prey animal wants predators popping in and out of sight, or demanding frontal views and preventing escape, all while the brain says, “Run!”

Groundwork

Most trainers use groundwork when starting young horses under saddle. Groundwork refers to any form of training in which the horse is not being ridden. We use it to teach leading, longeing, ground manners, and respect for human space. But we often forget that it’s useful in adult years as well, to teach a horse to back, spin, jump, or move laterally, for example. And it’s an excellent technique to revert to when problems arise.

The key is to realize that it’s a lot harder for horses to relax and learn while we’re sitting on them. So, step off and give them a better chance. Don’t worry, you’ll get back on again before the lesson is over. Remain quiet and calm, moving the horse with your eyes, hands, body position, voice, lead, reins, and/or a whip used only as an extension of your arm to touch the horse’s hindquarters. Groundwork does not require chasing a frightened horse in tight circles with flapping plastic bags tied to a stick. This is more properly called “frightwork,” in my opinion, and it usually causes more harm than good. Good groundwork takes skill and practice. Take the time to learn it well, and it will help your team.