What makes a good jumper horse?

A good jumper horse combines several specific physical and psychological qualities that together allow it to clear large, technically demanding fences consistently, respond to its rider's direction in the demanding situations that jumper courses create, and maintain the boldness and confidence needed to perform under competitive pressure. Scope — the horse's natural physical ability to clear fences significantly larger than it needs to in competition — is perhaps the most fundamental quality, because a horse that is jumping at the limit of its physical capacity cannot maintain accuracy under the speed and pressure of jumper competition. A horse that jumps with genuine power and careful technique in schooling can lose a rail at the same height in competition without scope to spare, while a horse with significant scope can lose a bit of technique under pressure and still clear. Carefulness — the horse's natural inclination to jump with its legs tucked up and away from the fence rather than being casual about rail contact — is closely related to scope and equally important, because a horse that is physically capable of jumping large fences but that tends to drag its legs through or brush rails will have inconsistent performance regardless of its scope. Boldness and confidence over unfamiliar fences, under pressure, and in complex situations — the willingness to gallop forward to a big fence when the horse can see a long distance, or to compress when the rider asks for a short add — is a psychological quality that distinguishes reliable jumpers from inconsistent ones. Trainability — the ability to learn and refine technique, to adjust to different distances and different types of fences, and to respond to the rider's direction in complex situations — makes the horse's athletic qualities available as a competitive resource rather than having them remain raw ability that cannot be consistently accessed under the variety of demands jumper courses present.