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One of the things that my dog agili­ty instruc­tor often says is “Reward your dog,” most often when the dog has done what the han­dler asked for, and not nec­es­sar­i­ly what the han­dler want­ed.

There are many ways in which dog agili­ty and rid­ing are dif­fer­ent. Dogs are not hors­es, in agili­ty you’re expect­ed to not be in con­stant con­tact with your dog, and seri­ous injury is less com­mon in agili­ty.

But there are some strik­ing sim­i­lar­i­ties. In both sports, novices overuse voice and hands to direct the ani­mal, while experts use tor­so and legs. Both are often faster-​paced than novices appre­ci­ate. Both require mus­cle mem­o­ry. And in both sports, an activ­i­ty that should ulti­mate­ly be reward­ing for the dog or horse can ini­tial­ly be scary.

Horse in a pastoral setting with a spaniel and a setter
Paint­ing by George Stubbs

Any time the dog or horse is doing what you ask, that’s praise­wor­thy, even if it wasn’t what you intend­ed. The reward is earned, and you should give it. Most dogs like food treats, or tug toys, or items they can chase, or that com­bine two or three of these attrib­ut­es. None of these work well for a rid­den horse—even food treats can only be giv­en at the halt, and the horse reach­ing for them dis­tracts from bal­ance and straight­ness and turns the halt into a stop. But the one thing almost every dog and horse (and human stu­dent) wants is reassurance—“You’re doing good!”

One way that hors­es bond with each oth­er is mutu­al groom­ing, and a com­mon groom­ing des­ti­na­tion is right in front of the rider’s hand: the area along side and in front of the with­ers. Because you’re the leader, when you scratch your horse there, you’re  telling him “I’ve got your back,” and when you’re rid­ing, you lit­er­al­ly do.

Relax­ing a rein to scratch is some­times coun­ter­pro­duc­tive when you’re being pre­cise with the aids, and that’s where the voice comes in. Hors­es reas­sure each oth­er by voice all the time, and while we can’t dupli­cate the details of what they’re say­ing to each oth­er, we can reas­sure by voice in a way they under­stand. Reas­sur­ing vocal­iza­tions gen­er­al­ly drop in pitch and vol­ume: “GOOD boy” (this is dif­fer­ent from dogs, where ris­ing pitch can elic­it excite­ment).

You might be think­ing that reward is impor­tant for train­ing, but is super­flu­ous for les­son hors­es and espe­cial­ly school­mas­ters, because they already know what to do. But they need rewards more than ever, not because you’re teach­ing them what to do, rather because they’re teach­ing you, and that’s how you let them know you appre­ci­ate the les­son. I’m not very good at that, because I often feel inept. But when your teacher is a horse, that’s real­ly the only way you can show grat­i­tude.

So now you have the tools. Reward your horse. Good boy!

2

Hors­es see a dif­fer­ent world than we do, in large part because of spe­cif­ic dif­fer­ences in their eyes. This arti­cle will focus on one aspect, the way horse and human eyes react to the col­ors of illu­mi­na­tion used for enhanc­ing human night vision. If you’re not inter­est­ed in the details, you can skip straight to the rec­om­men­da­tions.

Like humans, hors­es have two types of light-​sensitive cells in their reti­nas (the reti­na is the light-​sensitive lay­er at the back of the eye). Rods are sen­si­tive to very low lev­els of light, but don’t dis­crim­i­nate col­ors. Cones do the col­or dis­crim­i­na­tion, but need more light than rods to do their job. In humans, rods are about a hun­dred times more light-​sensitive than cones, and there’s no rea­son to expect hors­es to be any dif­fer­ent. Vision involv­ing the cones is called pho­topic vision and vision involv­ing the rods is sco­topic vision.

Photopic vision (colors)

Humans have three dif­fer­ent types of cone cells that absorb light of three dif­fer­ent wave­lengths: 420 nm (nanome­ters), which appears blue, 534 nm, which appears green, and 564 nm, which appears red. These are “peak sen­si­tiv­i­ties”; each type of cone detects wave­lengths short­er and longer than its peak, and there’s some over­lap. We have “trichro­mat­ic vision”, and all the dif­fer­ent col­ors we per­ceive are the result of our brains pro­cess­ing the sig­nals from these blue, green, and red cones.

Humans and oth­er pri­mates are unique among mam­mals in hav­ing trichro­mat­ic vision. Hors­es, dogs, and oth­er mam­mals have only two kinds of cone cells, and dichro­mat­ic vision. In hors­es, blue-​sensitive cones are most absorp­tive at 428 nm, and the oth­er type of cone is sen­si­tive at 539 nm, which appears yellow-​green to us. Some humans have protanopia, a type of color-​blindness in which the red cones don’t func­tion; a horse sees the world much like that.

Impor­tant for our pur­pos­es here, the yellow-​green cone can’t detect light with a longer wave­length than around 640 nm, which is a deep red.

Scotopic vision (“night vision”)

Hors­es have excep­tion­al night vision rel­a­tive to humans. Their eyes are larg­er than most oth­er land mam­mals, to gath­er more light. They have a tape­tum lay­er that reflects light back onto the reti­na (this is what caus­es eye­shine). And their reti­nas are rich­er in rods. In envi­ron­ments with moon­light, starlight, or even reflect­ed city lights, hors­es can see well enough to walk, trot, or even gal­lop with­out run­ning into things.

When a rod absorbs light, its visu­al pig­ment (rhodopsin, or “visu­al pur­ple” in old­er ref­er­ences) is irre­versibly changed (“bleached”), so that the cell’s abil­i­ty to detect light is reduced until new rhodopsin is syn­the­sized. In low light, rhodopsin is regen­er­at­ed as fast as it is used, but a burst of bright light can bleach all the rhodopsin in all the rod cells, and it can take thir­ty min­utes or more for the cells to ful­ly regain their abil­i­ty to func­tion. For rea­sons that are not entire­ly clear to me, humans regain a use­ful lev­el of night vision with­in five min­utes of being exposed to bright light, but hors­es need the full thir­ty min­utes. The same horse that can run across a pas­ture under the quar­ter moon can­not eas­i­ly dis­crim­i­nate details in a dark horse trail­er when asked to enter it from bright day­light.

Illumination for night vision

Humans have poor­er night vision than many oth­er ani­mals, and there are sit­u­a­tions where it’s advan­ta­geous to main­tain night vision even in the pres­ence of illu­mi­na­tion. There are two dif­fer­ent approach­es in cur­rent use.

The first to be devel­oped was the use of red light. Rod cells are insen­si­tive to red light, so they can stay adapt­ed to low-​light con­di­tions even while the red cone cells form images. Red night­time illu­mi­na­tion is still used in avi­a­tion and some mil­i­tary set­tings, and in dis­plays of some elec­tron­ic devices.

Red light has a cou­ple of dis­ad­van­tages for this use: it requires a high­er bright­ness, since it relies on pho­topic vision, and it’s some­times dif­fi­cult to dis­crim­i­nate shapes and near­ly impos­si­ble to dis­crim­i­nate col­ors.

A new­er alter­na­tive is to use bluish-​green light, at about the peak sen­si­tiv­i­ty of rod cells. Because this is the light that rods see best, extreme­ly low inten­si­ties can improve sco­topic vision with­out destroy­ing dark adap­ta­tion. In a sense, it’s like car­ry­ing around a full moon.

The effect of these two types of light on hors­es is total­ly dif­fer­ent. Like humans, hors­es can­not see red with their rod cells, but they also can­not see it (or see it only dim­ly if it’s more of an orange-​red) with their yellow-​green cone cells. A human anal­o­gy is an infrared remote for an enter­tain­ment sys­tem: most peo­ple can­not see the beam even if it is shin­ing direct­ly in their eyes. For hors­es, deep red is “infra-​yellow-​green”, not real­ly a per­ceived col­or at all.

Horse's eye open under red light on left, squinting under green light on right
Red light pre­serves hors­es’ night vision. At a bright­ness lev­el high enough to be use­ful to humans, green light impairs their night vision.

And because hors­es have more rods, and more sen­si­tive rods, than humans, a low-​intensity bluish-​green light, bare­ly per­cep­ti­ble to a human, would be much brighter to a horse, and would reduce their night vision.

Recommendations

  1.  Red light pre­serves both human and horse night vision. Hors­es only see it dim­ly if at all, and con­tin­ue to rely on their superb night vision. It allows humans to per­ceive shapes and see text and dia­grams that would be much less vis­i­ble with the infe­ri­or human night vision, but at the same time pre­serves that night vision for see­ing in areas where the beam is not direct­ed.
  2. The bluish-​green light used for enhanc­ing human night vision is inap­pro­pri­ate for hors­es. It is only effec­tive for pre­serv­ing night vision in humans at the low­est lev­el of bright­ness that a human can use­ful­ly per­ceive, and this is much brighter that the low­est lev­el that a horse can per­ceive. If the human can see it, the horse’s night vision is already impaired.
  3. Red head­lamps or flash­lights are use­ful for night trail rid­ing; they have no effect on the horse’s night vision, and aug­ment the human’s night vision. The use of white light head­lamps or flash­lights is strong­ly dis­cour­aged; they destroy night vision in both hors­es and humans in exchange for pro­vid­ing only a nar­row area of illu­mi­na­tion, and when they are switched off, hors­es need much longer to regain night vision than humans, and are effec­tive­ly stum­bling in the dark until they do.
  4. Red LED illu­mi­na­tion may be more use­ful for barns and out­door sta­bles than the usu­al flu­o­res­cent light­ing. It allows a human to deal with a spe­cif­ic horse with­out destroy­ing the night vision of all the oth­er hors­es in the facil­i­ty. Hors­es dif­fer in their response to “hav­ing the lights turned on”, but even for the most non­re­ac­tive horse, it’s one more thing to put up with. In my ide­al facil­i­ty, there would be red light illu­mi­na­tion every­where that would go on with a sin­gle switch, so I could walk down the aisle with­out trip­ping on some­thing. Each stall could have an indi­vid­ual white flood lamp, or I could car­ry a white head­lamp or flash­light, if I need­ed bet­ter vision for a spe­cif­ic horse.

Exec­u­tive sum­ma­ry: Red light, yes. Green light, no.