I learn by watching. I like to study how people warm up, how horses react to certain types of rides, and even how horses look as they are exiting the show arena. I think if you watch closely, there is an enormous amount of information that you can gather from simply observing horses go.
Riders tend to be protective of their horses—we treat them like our children, and we want them to always have good experiences. We might trust our trainer to ride them, but otherwise we would often prefer that they not be ridden at all than be ridden by someone else.
I actually think this logic is flawed, and that letting someone else ride your horse can be really educational. I sometimes teach lessons on my own horses. This scenario starts more out of necessity than anything else: I might have a student with a lame or shoeless horse, or a student who doesn’t currently own or lease a horse but still wants to take lessons. Or sometimes I’m not teaching the person, but just letting them get some saddle time, either doing flatwork in the ring or going out hacking. In any case, I let people ride my horses occasionally, as long as I know that they will be safe.
I used to see this as doing a favor for the student or friend, but sometimes it actually does a favor for me. I was teaching a student on a young horse a few weeks ago, and I realized that the horse was super loose and relaxed when warmed up in a lower frame. I could see a huge difference from the ground—more than I would have felt under saddle. And I could also tell that this was what that horse needed in order to build strength.
Watching someone else ride your horse can also be a really interesting fact-finding mission. If the rider is a bit more novice than you, then you can actually see how well your horse is trained (or not!). If the horse is disobedient in some way, then you know that you have work to do on that particular area. Or maybe they are not particularly responsive for a different rider—then you know that the horse needs to be trained to go more on the aids. A horse will default to its base level of training, and if that default isn’t what you envisioned, then you know what to improve going forward.
Obviously jumping carries more risk than flatwork, so you want to really trust someone to let them jump your horse. But this, too, can be informative to watch. Does your horse tend to drift (and does he do it more or less with the other rider than he does with you)? Does he give a good shape over the jump, and is he responsive to half-halts? This new information can help you hone in on what to focus on in your own training.
Back in my Pony Club days, we used to swap horses with our peers fairly frequently. This switch-riding was actually required for many of the upper-level certifications, so that the examiners could see how riders handled different types of horses. I always found it interesting to watch how my horse went under other riders. We have to remember that when we’re on the horse, we cannot see what he looks like in real-time. Of course we can review videos, and maybe if we’re lucky we can glance in the arena mirror. But this is not the same as studying someone else ride your horse, which can be a really useful tool for amateurs, juniors, and pros alike.