We all have “what we can live with” in our horses, and it can vary a great deal between people. Driver experience, KNOWING YOUR HORSE can let you be accepting of a behavior that would terrify anther person.
We have had a couple “lively” ones over the years, various breeds, that we learned from. One was a old breeding (pre-1980s) Gelderlander mare ( they don’t breed them anymore, she was a dinosaur), who got VERY excited being hitched. We knew some of her history, led a “must perform” life, with scars to prove it. She would rear, kind of up like the Lippazans medium high, stand up there, then come dowm. This was after all harness was attached to the vehicle, so we COULD have driven off safely, but were waiting to get everything loaded and in place first. Her old partner was quiet, calm, usually able to lean away from her to avoid any bumping. We had someone heading them with lead ropes on each horse until Driver said “Turn them loose”. We put up with it. She was an old horse, this was a nervous reaction to being driven. It never got worse, never changed to other things. She just “bounced in place” as we called it, not scary TO US because she was always the same. She was a wonderful horse going, taught us a great deal about how an Advanced gorse should move, feel in various gaits. FAST with 5 trots to make your eyes water, true extentions reaching way out there! Not pretty faced, but a HECK of a fine horse. She and her partner got our young horses going as a Four, we really liked her. We did finally get her over the rearing, standing to start off! It was kind of accidental. Husband called and said if we got the horses harnessed and hitched, he could be home at xx time to drive them. So we got around, had them ready, headed, waiting for him. Well he didn’t arrive, was pre-cell phone time. While standing there she did her antics, then scaled down to pawing, prancing in place, until I said we need to unhitch. 30 minutes is a long enough wait for husband. So we took them off the vehicle, mare gave us the funniest look! “We are not going driving after all that?!” Took them back in the barn, got unharnessed and stalled them. Husband got home an hour after planned arrival, had been trapped in traffic. Same thing happened about 2 weeks later, he planned to be home, we had horses ready, hitched, he never arrived. So we waited again, mare quickly ran thru her “tricks” to then stand pretty quietly while waiting. I was pretty surprised she settled. Again waited about 30 minutes before giving up on husband. She again acted quite confused when we unhitched, unharnessed, put the horses out in pasture because it was nearing dusk. But she seldom went thru her serious antics again, standing hitched to a vehicle. The waiting around, no work, unhitching to go back to the barn clicked something in her brain. We still got some head tossing, but almost never reared again. That Pair was a gift, old but sound, imported, trained to ridden Grand Prix thru the Dutch school, just awesome horses. Both had lovely, honest eyes.
We had heard Hackney Horses could act similarly from Coachmen that drove Hackneys. Lots of fire, but the horses never went actually crazy, more that they got light in front with half rears, impatiently waiting to go. Again, not scary to those used to those kind of horses, that way of horse thinking. Probably why the Safety Rules for using Header to hitch and unhitch at shows, competitions got put in place!
People who are skilled horse people enjoy alert, big moving horses who are not lugging on their hands. Like the flashy action, movement of those Breeds, both ridden and driven. Perhaps like the responsiveness too, like sports cars over driving a Grampa car.
Our experiences with show Saddlebreds is that they are usually extremely regimented, in handling, exercise, stabling. All the Trainers seem to do things the same. Things happen as scheduled, no more, no less! Horse knows the exercise routine, will do it even if a person is not directing him! Horse gets upset when routine is not followed! Husband is a Farrier, does Saddlebreds, meets them at boarding barns. He often has to educate new owners, stable help on what horse expects, horse is not “silly or crazy”, people are messing up his routine! Can’t leave him out loose in a paddock with flies biting him! Not part of his routine. He will usuall be perfect to handle if you do things as he was trained to expect them. A Diva in truth, not a “regular” horse to handle.
The Dutch Harness horses are probably similar, more sensitive, so also reactive. Not the horse for everyone, even as partbreds in the driving or ridden areas. For the Amish, they are fast road horses, crossbreds still have speed but not the same prices as purebreds. And most of their horses WORK DAILY to actually GET TIRED which is not true for us other horse owners! Those horses are glad to stand or walk if asked.
Modern horses are not used the way they were in the past, but still have the original qualities to work, energy for a full days labors, some no-quit, with no place to use it. So the energy may get directed into less desirable behaviors when we want just enjoy them for a short time. And it is easy to be breed prejudiced, good or bad, because breeders DO TRY to stick to Breed standards. Like buying working dogs and expecting them to act quiet in a house with little exercise or brain stimulation. Those breeds NEED JOBS to be happy dogs. Most such dogs start acting destructive, are problem pets without ever getting OUT or TON of activity with owners. It is very hard to tire them out.
There are many horse breeds, crossbreds to suit any owner. When driving folks say “sane” they usually mean non-reactive to scary things. That is a good brained horse who has also BEEN TRAINED to not react badly to various stimuli. People need to pick an animal suitable for THEIR driving and riding desires. No use buying the Beautiful Black Stallion if you only plan a short trail drive once a week, he will hurt you! Get a nice placid, older pony/horse instead. It could still be black! Ha ha.