How Horses’ Mem­o­ries Work

Un­der­stand­ing how it works can help you train and care for your horse.

Practical Horseman - - Contents - By Elaine Pas­coe with Sue McDon­nell, MS, PhD, and Leanne Proops, MSc, PhD

Un­der­stand­ing how bi­ol­ogy and be­hav­ior shape equine mem­ory will al­low you to bet­ter train and care for your horse.

Life is all mem­ory, ex­cept for the one present mo­ment,” the play­wright Ten­nessee Wil­liams wrote. It’s true. Even when we’re not think­ing about the past, we’re min­ing mem­ory for in­for­ma­tion and guid­ance that will help us nav­i­gate life. What about your horse? What role does his mem­ory play, and how does it af­fect your in­ter­ac­tions with him? The Magic 8 Ball would have to say, “Re­ply hazy.” Mem­ory just hasn’t been stud­ied in horses as much as in peo­ple or other an­i­mals. But some re­search has been done and new in­for­ma­tion is emerg­ing.

Equine be­hav­ior ex­perts Sue McDon­nell, PhD, found­ing head of the equine be­hav­ior pro­gram at the Univer­sity of Penn­syl­va­nia School of Ve­teri­nary Medicine’s New Bolton Cen­ter, and Leanne Proops, PhD, a com­par­a­tive psy­chol­o­gist and ethol­o­gist at the Univer­sity of Portsmouth in Eng­land, shared their in­sights. Evo­lu­tion shaped the way horses form, re­tain and use mem­o­ries, they say, so equine mem­ory dif­fers from hu­man mem­ory in key ways. Un­der­stand­ing how it works can help you train and care for your horse.

Mak­ing Mem­o­ries

Some ba­sic ideas about mem­ory seem to ap­ply across species, the ex­perts agree. One thought is that mem­o­ries come in two ba­sic types:

Im­plicit mem­o­ries guide ac­tions and re-

sponses be­hind the scenes, in ways you’re un­aware of. If you’ve been rid­ing long enough, for ex­am­ple, you don’t con­sciously re­mem­ber how to get on a horse—you just do it.

Ex­plicit mem­o­ries are those you con­sciously re­call. If you trip on a cer­tain path, say, you re­mem­ber and watch the foot­ing more closely the next time you go that way.

When most peo­ple talk about mem­ory, they’re re­fer­ring to the ex­plicit type. Horses build these mem­o­ries the same way you do—by forg­ing con­nec­tions be­tween brain cells called neu­rons.

The brain has bil­lions of neu­rons, con­stantly sig­nal­ing to each other. Hold out a car­rot to your horse, and you trig­ger neu­rons ded­i­cated to sight and smell. They fire, re­leas­ing chem­i­cal mes­sen­gers (neu­ro­trans­mit­ters) across junc­tions (synapses) be­tween cells. The neu­ro­trans­mit­ters at­tach to re­cep­tors on the next neu­ron, prompt­ing it to fire and pass the mes­sage

on. In a flash, the brain shoots back a call to ac­tion: Get the car­rot.

The first time a horse sees a car­rot, he may hes­i­tate be­fore tak­ing it. Next time he’ll take it faster. That’s be­cause, as a ba­sic prin­ci­ple of neu­rol­ogy states, “neu­rons that fire to­gether wire to­gether.” The chem­i­cal mes­sages form links be­tween neu­rons, and re­peated fir­ing strength­ens the links. These links are the ba­sis of mem­o­ries.

How he’s dif­fer­ent: You re­mem­ber not only your ex­pe­ri­ences but also knowl­edge you glean secondhand, from me­dia, school, friends, fam­ily and other sources. So far as we know, horses don’t swap sto­ries around the wa­ter trough or pass on an­cient horse lore late at night in the barn. Their mem­o­ries are based on ex­pe­ri­ence alone.

But horses may out­shine peo­ple in as­so­cia­tive mem­ory, the abil­ity to forge and re­tain links be­tween ap­par­ently un­re­lated things. As­so­cia­tive mem­o­ries form when groups of brain cells that are ac­tive at the same time sync up, so that ac­tiv­ity in one group fa­cil­i­tates ac­tiv­ity in the other.

“Horses are good at form­ing these mem­o­ries be­cause they evolved as open plains-graz­ing an­i­mals. Link­ing ex­pe­ri­ences to cir­cum­stances—phys­i­cal sur­round­ings, sounds, scents, ev­ery­thing—helped them sur­vive,” says Dr. McDon­nell. A horse would re­mem­ber where a lion at­tack oc- curred and steer clear of the place. To­day, she says, horses still have “al­most pho­to­graphic mem­ory of the cir­cum­stances sur­round­ing neg­a­tive ex­pe­ri­ences. They re­mem­ber what vet­eri­nar­i­ans wear and what they smell like, and they re­mem­ber the sounds of the far­rier’s truck.

“Horses on the plains also de­vel­oped com­plex pos­i­tive mem­o­ries, for ex­am­ple, of places where wa­ter and food were found,” she adds. “The horses that could form these as­so­ci­a­tions were the ones that sur­vived.”

Re­search in other species sug­gests that body chem­istry helps etch some ex­pe­ri­ences in mem­ory. Stress hor­mones such as cor­ti­sol and ep­i­neph­rine, re­leased dur­ing painful and stress­ful events, may strengthen neu­ral con­nec­tions. Brain chem­i­cals as­so­ci­ated with plea­sure may help strengthen pos­i­tive mem­o­ries.

Good to know: “Peo­ple of­ten fail to un­der­stand how quickly horses form these mem­o­ries and how strong they are,” Dr. McDon­nell says. “Horses dis­play what psy­chol­o­gists call sin­gle-trial aver­sion learn­ing, which means that one bad ex­pe­ri­ence on a trailer may leave a horse per­ma­nently un­will­ing to load.” Case in point: Tem­ple Grandin, PhD, a pro­fes­sor of an­i­mal science at Colorado State Univer­sity and au­thor of An­i­mals in Trans­la­tion (Scrib­ner, 2005) and other books, de­scribes a horse that had once been abused by some­one wear­ing a black cow­boy hat and re­mained ter­ri­fied of black cow­boy hats ever af­ter.

It’s eas­ier to pre­vent neg­a­tive as­so­ci­a­tions than to erase them, Dr. McDon­nell says. You can do this through ac­cli­ma­tion, grad­u­ally in­tro­duc­ing any­thing po­ten­tially scary so the horse can get used to it.

“We’ve found that the process is eas­i­est when the horse feels in con­trol of the sit­u­a­tion,” she says. “When you in­tro­duce clip­pers, for ex­am­ple, start with the clip­pers off and let him ex­plore them. When he touches them with his nose, re­ward him with a treat. He’ll quickly learn to reach out and touch the clip­pers for his re­ward. Then re­peat the ex­er­cise with the clip­pers on. When he touches them, turn them off and give a treat.” The horse comes to as­so­ci­ate clip­pers with treats rather than learn­ing to fear them.

Keep­ing Mem­o­ries

Horses seem to share our abil­ity to form long-term mem­o­ries that per­sist for hours, days, weeks or years, says Dr. Proops. She points to sev­eral stud­ies done in the early 2000s by Eve­lyn Hanggi, PhD, co-direc­tor at the Equine Re­search Foun­da­tion in Ap­tos, Cal­i­for­nia. “In one, horses learned to as­so­ci­ate spe­cific sym­bols and ob­jects with a re­ward. They were pre­sented with these prompts six years later and still re­mem­bered them.”

No one knows if there’s a limit to how long horses re­tain mem­o­ries. Cog­ni­tive sci­en­tists say the longevity of hu­man mem­o­ries hangs on how strongly they’re en­coded, and that de­pends on sev­eral fac­tors:

Rep­e­ti­tion. Links be­tween neu­rons strengthen when they’re used and weaken when they’re not, so re­peat­edly ac­ti­vat­ing neu­ral net­works in­volved in a par­tic­u­lar mem­ory makes that mem­ory stronger.

Im­por­tance. You’re more likely to re­mem­ber some­thing if it’s im­por­tant to you, and the same is true for your horse.

Per­cep­tion. How acutely the brain ini­tially per­ceives the sub­ject of a mem­ory af­fects how strongly the mem­ory is en­coded.

How he’s dif­fer­ent: Your horse doesn’t share your pri­or­i­ties. For him, the most im­por­tant (and mem­o­rable) things are re­lated to sur­vival—get­ting food and avoid­ing preda­tors. And while you may both be in the same place at the same time, he prob­a­bly per­ceives the sur­round­ings dif­fer­ently. He notes and re­mem­bers every gran­u­lar de­tail, Dr. Proops says, be­cause even a sub­tle change in the en­vi­ron­ment may rep­re­sent a dan­ger to prey an­i­mals like horses.

Good to know: Un­der­stand­ing how long-term mem­o­ries are strength­ened can help you in train­ing. Rep­e­ti­tion is an es­sen­tial train­ing tool, for ex­am­ple. A good trainer may get a young horse to pick up the cor­rect can­ter lead in one ses­sion, but she won’t ex­pect the horse to take his leads re­li­ably with­out many rep­e­ti­tions over many, many days. Once the horse learns, though, he’ll re­mem­ber af­ter months or years with­out be­ing drilled.

Pos­i­tive or neg­a­tive re­in­force­ments can make the be­hav­ior more im­por­tant to the horse. Dr. McDon­nell says, “In most cases the trainer prompts the de­sired be­hav­ior by guid­ing the horse with pres­sure (a neg­a­tive) and re­wards the be­hav­ior by re­leas­ing pres­sure. But if the be­hav­ior is evoked with some­thing pos­i­tive, the horse learns faster and re­mem­bers bet­ter. There’s no ques­tion that pos­i­tive train­ing meth­ods are more ef­fi­cient.” That’s the the­ory be­hind re­ward-based sys­tems like clicker train­ing. The horse learns to as­so­ci­ate a click with a food re­ward, so the trainer can in­stantly re­ward be­hav­ior us­ing a quick click as a stand-in for the food.

Sur­vival-driven hy­per­aware­ness helps ex­plain why a horse may spook at some­thing you don’t even no­tice, like a trash can moved to a new spot out­side the barn. He’s not be­ing will­ful—he knows it wasn’t there be­fore, so to him it’s a po­ten­tial threat.

But why, af­ter the horse gets over his shock at see­ing the can on his right as he

ex­its the barn, does he spook again when he passes it on his left as he re­turns? “Hav­ing a ‘split brain,’ an ex­pla­na­tion I’ve heard for this be­hav­ior, isn’t cor­rect—in­for­ma­tion does cross over from one side of the horse’s brain to the other,” Dr. Proops says. “The re­sponse is prob­a­bly sim­ply be­cause the po­ten­tial threat is seen in a dif­fer­ent con­text.”

Con­texts and Con­cepts

Hu­mans stand apart in their ad­vanced abil­ity to gen­er­al­ize—to form broad con­cepts from spe­cific facts by iden­ti­fy­ing com­mon prop­er­ties and to ap­ply those con­cepts in new con­texts. But there’s plenty of ev­i­dence that horses can do this, too, if to a lesser de­gree.

In one study, Dr. Hanggi taught horses to dis­crim­i­nate be­tween paired pic­tures of shapes (cir­cles, tri­an­gles and oth­ers) with ei­ther open or solid black cen­ters. The horses got a food re­ward for pick­ing the open-cen­ter shape in each pair. When they were con­sis­tently pass­ing the test, they were pre­sented with paired pic­tures of new shapes, also with solid or open cen­ters. They im­me­di­ately picked the open-cen­ter pic­tures.

In other stud­ies horses showed that they un­der­stood the con­cept of rel­a­tive size, learn­ing to choose the largest or small­est im­age or ob­ject in a group. Dr. McDon­nell’s team has done some sim­i­lar work, so far un­pub­lished.

“Eye po­si­tion makes it dif­fi­cult for horses to an­a­lyze a two-di­men­sional ob­ject di­rectly ahead, so for our work we used 3-D ob­jects,” she says. “And be­cause horses are ex­cel­lent at de­ter­min­ing the firm­ness of the ground, we tested the con­cept of rel­a­tive den­sity of ob­jects.”

The team placed blocks of dif­fer­ent den­si­ties on the ground and re­warded horses for se­lect­ing the one with the “right” firm­ness. For half of the horses the cor­rect choice was the softer of the two blocks, and for oth­ers it was the firmer.

“Once they were choos­ing their cor­rect re­sponse of those two blocks, we pre­sented blocks of a wide vari­a­tion of den­si­ties in pairs. Their task was to touch each and then se­lect ei­ther the softer or the firmer of that pair,” Dr. McDon­nell says. “In a se­ries of 20 pre­sen­ta­tions, all the horses achieved ac­cu­racy above what would be ex­pected by chance, most choos­ing cor­rectly on every pre­sen­ta­tion.”

The re­sults of these stud­ies show that horses can form, re­mem­ber and ap­ply con­cepts, in­clud­ing rel­a­tive con­cepts like size and den­sity. Horses also show what cog­ni­tive sci­en­tists call ob­ject per­ma­nence, the abil­ity to rec­og­nize a three­d­i­men­sional ob­ject when they see it in a dif­fer­ent po­si­tion.

How he’s dif­fer­ent: Anatomy helps ex­plain your abil­ity to out­per­form your horse in con­cept for­ma­tion. Positron emis-

sion to­mog­ra­phy scans, which track brain ac­tiv­ity, show that a struc­ture called the hip­pocam­pus is crit­i­cal to mem­ory and highly ac­tive when peo­ple form con­cepts. It passes in­for­ma­tion to the pre­frontal cor­tex, an area that’s some­times called the brain’s chief ex­ec­u­tive for its role in de­ci­sion-mak­ing and other high-level op­er­a­tions.

Your horse also has these struc­tures. It’s likely that they’re sim­i­larly in­volved in mem­ory and con­cept for­ma­tion, al­though no one has done a PET scan to prove it. But your pre­frontal cor­tex is larger and far more de­vel­oped than your horse’s, en­abling you to carry out com­plex men­tal tasks. This dif­fer­ence gives you an edge in ap­ply­ing con­cepts to make sense of the world.

For horses, Dr. Proops says, “How eas­ily a learned be­hav­ior is gen­er­al­ized will partly de­pend on the na­ture of the be­hav­ior.” Be­hav­iors with pos­i­tive as­so­ci­a­tions, such as touch­ing an ob­ject to get a food re­ward, may be more eas­ily gen­er­al­ized than be­hav­iors learned in the con­text of fear, such as stay­ing re­laxed in the face of a flap­ping flag. “It doesn’t make adap­tive sense to gen­er­al­ize widely re­garded po­ten­tial threats—you may over­look a real threat and get eaten!” she says. So, a horse may learn to ig­nore a flag he sees rou­tinely at home but still re­act to a flag in an­other con­text.

Good to know: “To over­come a par­tic­u­lar fear, the horse must first be­come re­laxed in one con­text,” Dr. Proops says. “Then you can slightly change the con­text un­til the horse is re­laxed there, and then change the con­text again.” As the horse gets more used to killer flags or what­ever trig­gers his fear, the new con­texts can be­come more var­ied. But, she says, “At the out­set, they should be quite sim­i­lar to the con­text the horse has al­ready learned is safe. The closer the new con­text is to the learned con­text, the eas­ier gen­er­al­iza­tion will be.”

Be­hav­ior­ists call this ap­proach sys­tem­atic de­sen­si­ti­za­tion. An­other use­ful ap­proach is coun­ter­con­di­tion­ing, teach­ing a new be­hav­ior to re­place an un­wanted one. “If a horse feels threat­ened and throws his head up when you han­dle his ears, for ex­am­ple, use re­wards to teach him to tar­get the ground in­stead,” Dr. McDon­nell sug­gests. That way you link ear han­dling to a pos­i­tive as­so­ci­a­tion in place of a neg­a­tive one.

The burned-in na­ture of fear-based mem­o­ries means that un­wanted be­hav­iors can resur­face long af­ter you think they’re gone for good. But you stand the best chance of suc­cess with pa­tience and a pos­i­tive ap­proach. “It helps to take as many neg­a­tives as you can out of the ex­pe­ri­ence,” Dr. McDon­nell notes. “We don’t al­ways re­al­ize what the horse per­ceives as neg­a­tive. Re­straint or con­fine­ment, for ex­am­ple, can con­trib­ute to panic.”

Hold out a car­rot to your horse and you trig­ger brain cells (neu­rons) ded­i­cated to sight and smell. They fire, re­leas­ing chem­i­cal mes­sen­gers across junc­tions be­tween neu­rons. In a flash, the brain shoots back a call to ac­tion: Get the car­rot. The mes­sages form links be­tween neu­rons, and re­peated fir­ing strength­ens the links, which are the ba­sis of mem­o­ries.

Wild horses have fine-tuned their sur­vival in­stincts as open plains-graz­ing an­i­mals by rec­og­niz­ing dan­ger­ous sit­u­a­tions and re­mem­ber­ing where to find food and wa­ter sources.

Re­ward-based teach­ing meth­ods, such as clicker train­ing, are a pos­i­tive way to help a horse learn some­thing new.

Spook­ing doesn’t nec­es­sar­ily mean your horse is be­ing naughty. He is uti­liz­ing his sur­vival-driven hy­per­aware­ness and might con­sider new ob­jects in his sur­round­ings a po­ten­tial threat.

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