up patterns in the external world, transform them into neural impulses, and send them to the brain for interpretation. Tiny differences in loudness and pitch are critical to comprehending human speech, tonal emotion, music, environmental noises, and animal vocalizations. A horse or human who can’t discriminate sounds well is going to have some trouble communicating.
So, once a horse’s ears pick up a sound wave and send it to that squashed grapefruit called his brain, what happens there? All sorts of things. We often study those processes by considering what happens when the brain isn’t doing its job. Humans with good ears but damage to the auditory cortex often experience auditory agnosia (“ag-NO-zhuh”). The sounds come in, but they don’t make sense. Patients report that sounds—often voices—are too loud, unpleasant, blurred, crackling, echoing, sometimes painful. They’re not sure whether a sound is real, but they usually don’t realize that anything is wrong with their brains. Instead, these patients complain that the noises themselves are to blame for the misperception.
Intact human and equine brains order sounds, allowing some tones to fade into the background and others to come forward. They become accustomed to typical sounds and use atypical ones as warning signals. They associate learned sounds with sights, smells, touches, knowledge, or experiences. What horse, for example, does not link the sound of the feed truck or bucket with the time of day?
Thanks to their brains, horses are whiz kids at interpreting the whinnies, nickers, snorts, blows, groans, snores, and squeals of daily equine life. A horse can hear one whinny and know who’s calling, what mood he’s in, and what he wants. Horses whose owners arrive by car to feed them will nicker a greeting when that car arrives, yet ignore other cars. They know who’s who. Some ignore all transport rigs except their own, heading to the farthest corner of a pasture when the trailer arrives, as if to say, “No, thanks, I’d rather stay home.”
Stories abound: Have you heard about the retired circus horse who knew the command “high” as an instruction to rear? It worked all too well around his retirement barn when folks said, “Hi,” to each other. How about the American import who refused to canter on a longe until the English handler faked a strong American accent to pronounce the command, “Canter?” Once the horse understood the word, he picked up the gait.
Horses scope out a wide range of human emotion from tone of voice, and they respond to it well. A horse who knows to hold still while being tacked up, for example, might wiggle while the handler murmurs, “Oh, stop that,” or even voices a known command like, “Stand.” But the minute a respected handler says the same words in a sharp sudden tone, the horse reverts to good manners. Of course, he has learned the desired behavior in advance—unfortunately, we can’t just train a horse from scratch by speaking louder. If only!
Music
Normal human brains interpret certain pitch patterns as music. We take this ability for granted because it feels completely effortless and is common among almost all people. To comprehend music, though, our brains are working up a sweat. They have to analyze:
Relationships between pitch, time, and volume
Variations and consistencies in grouping and phrasing
Patterns of rhythm and tempo
Expectations based on memory
Sensory illusions designed by the composer
Emotion
This is complicated stuff.
I am often reminded of musical rhythm while riding—a horse who’s “behind the leg” is much like a singer behind the beat. And like music, the location of the rhythmic pocket changes with riding discipline: We teach Western Pleasure horses to work behind the leg, jumpers to work in front of it, and trail horses to stay on it.
Rarely, specific damage to the brain interferes with music perception. When listening to a song, people with amusia (“uh-MYOO-zhuh”) hear random disconnected tones. One patient, formerly a music composer and performer, described her post-injury perception as a collection of equal notes in which no one instrument or tone emerges as superior to the rest: “When I listen to an orchestra I hear 20 intense laser voices [each belonging to a separate instrument]. It is extremely difficult to integrate all these different voices into some entity that makes sense.”
An even tinier handful of people have congenital amusia, a lifelong disability in which their hearing is fine and their brains are normal in every other way. One described listening to a lilting lullaby like this: “If you were in my kitchen and threw all the pots and pans on the floor, that’s what I hear!”
We can infer that horses perceive music. It certainly has an effect on them that is different from the sound of kitchen pans landing on a floor. The equine brain is calmed by lyrical tunes without sudden changes in volume. Horses prefer Mozart to Beethoven, soft rock over techno, and country or folk more than heavy metal. Dissonant music agitates them, so it’s best to leave Stravinsky at home. Human brainwaves synchronize when a group of people listen to music together. Chances are that the same synchrony occurs among horses.
Despite the complexity of music perception, the horse’s brain makes sense of tonal patterns. How do we know this? Because his emotions change when listening to varied types of music. Even more intriguing, the same correspondences between music and emotion occur in a human as in a horse. A song that relaxes, invigorates, or annoys us is likely to have the same effect on our animals.
Winning with Music
A recent study explored the effects of music on Arabian racehorses. Thirty of them were housed in a barn where harmonious background music was played for five hours every afternoon. Forty of their peers were in a different barn at the same facility where there was no music. Conditions like feed, exercise, companionship, cleanliness, and handling were held constant. Within a month, the Arabians exposed to daily music developed significantly lower heart rates and won their races more often.
The positive effect lasted for three months. After that, the horses became accustomed to the music and its effect waned. But three months is long enough for a good trainer to change a smart aleck who becomes relaxed enough to learn. Once that foundation is set, the horse will remain trainable for the long term.
Where’s That Sound?
A third aspect of hearing is sound localization. Close your eyes and listen for a noise. (Have a friend hide a timer and set it to ring quietly in a few minutes, if necessary.) When you hear the noise, you know where it’s coming from—behind you, from one side or another, above, below, or from some angle in front of you. Horses seem to be likely candidates for localization genius: They have large cupped ears with a turning radius of 180 degrees front to back and about 90 degrees top to side. Sixteen muscles per ear are devoted to flicking all that cartilage around quickly and accurately. These movements operate independently, so one ear can be pointed toward the front, for example, and the other toward the back. Fur protects equine ears from insect bites, cold, foreign objects, dirt, and rain, so they can function well.
In addition, equine ears are set far apart, which increases the time difference in the arrival of a sound as it approaches the horse’s head. This is a key feature for good localization. Physically, a sound is a wave of air molecules that strikes the eardrum. Suppose the wave is coming toward the left side of the head. This sound will arrive in the left ear before it arrives in the right. The greater the distance between ears, the greater the difference in arrival time. This tiny interval tells the brain that the sound is coming from the left. The horse—or human—then knows to turn to the left and look for more information or run toward the right to escape potential harm.
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