After several thousand generations of domestication, we now have horses whose bodies and brains are mostly naturally selected, but whose behavioral traits of calmness and acquiescence are largely artificially selected. Variation among breeds is also a feature of artificial selection. The American Thoroughbred, for example, is bred to be light, long, lean, and agile—perfect for speed. Belgian Warmbloods are bred to be bulky, thick-muscled, wide, and slow—great for power. Along with these physical traits come differences in temperament, with the flighty nervous racehorse contrasting the stolid reliable Belgian. Within each breed there are individual differences, of course.
Today’s Brain
Throughout evolution, brains have become bigger. Yet brain function in both horses and humans is determined far more by neural connection than absolute size. According to the Internet, the horse’s brain is the size of a walnut. Or a human fist. Three baseballs. Next thing ya know, they’ll be likening it to a peanut or a watermelon. Sounds like some facts are in order.
Pop a human brain out of its skull and you have a 3-pound lump of squishy tofu that’s 75% water. The average horse’s brain has the same consistency but weighs 1 pound 5 ounces, not quite half the weight of its human counterpart. A basketball weighs the same, as does the brain of a six-month-old human baby. In terms of size, the adult human brain is about 4 inches high, 6 inches wide, and 7 inches long. The tissue of both the human and horse brain is especially dense in some areas, often corresponding to “structures” that are identified in diagrams.
The horse’s brain is about the volume of a grapefruit. In shape, the grapefruit is elongated and partly squashed. It’s lumpy and bumpy but measures about 4 inches high, 4 inches side to side, and 6 inches front to back. It rests on a 45-degree angle pointing downward rather than sitting level as a human brain does.
Most important for function, the horse’s brain contains slightly over 1 billion neurons, far fewer than the human brain’s 86 billion. Depending on its type, each neuron can accept up to 10,000 connections. These connections are the magic behind equine perception, learning, emotion, and athleticism.
Brain Change through Maturation and Learning
One of the linchpins to any form of animal training—or human learning, for that matter—is to identify what can be changed and what cannot be changed. We’ve seen that evolution drives certain equine behaviors that are innate and physiological. By respecting them, we reduce the horse’s fear and can then alter more malleable aspects of his brain.
Brain connections are built by daily experience. Few people realize just how physical a process learning is. When a foal takes that first step toward you, a new physical connection within a group of brain cells is formed. It’s weak, it will disappear if it’s not repeated, and it’s prone to mistakes. But every time the fledgling connection is used, it becomes stronger. The foal’s second step forward strengthens it, tomorrow’s positive approach reinforces it, and so on. Eventually you have built a brand new network of connected neurons inside your foal’s brain that forms an initial bond.
That one physical connection is the basis for everything the foal will do in the human world. You will build on it, little by little, until this baby trots at your shoulder, halts on a slack lead when your feet stop moving, follows verbal commands, accepts a saddle and rider, 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
