Horse Brain, Human Brain. Janet Jones

learns to jump, wins a world championship, retires with you to the trails, and eventually enters the old-age pasture.

      Neural connections form throughout all of life, so you can continue to shape your horse’s brain—and your own—until the day one of you leaves this earth behind. Pause for a moment to think about the immensity of that power. And the responsibility that comes with it. You are shaping your horse’s physical brain, and he is shaping yours. That is an extraordinary—almost supernatural—ability. Cherish it.

      Reflex Action

      If human perception and action are mediated by thought, you might wonder how we so rapidly avoid pain. Automatic reflex actions are responsible for that—and the brain does not control them. Next time you touch a hot stove burner (please do not try this at home!), notice how your arm instantaneously pulls away. This action occurs at the level of the spinal cord, before the pain signal has time to reach the brain. No thought is involved. Horses experience reflex actions when they shake flies off their skin, shiver in the cold, cough, swallow, suckle, or blink.

      Hard-Wired Fears

      Natural selection causes horses to fear:

       restriction

       confinement

       darkness or narrow passages

       sudden movements

       unusual sounds

       predators

       isolation from the group

      Part Two

      Taking the World In

      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