What is the concept of pressure and release when training?

Pressure and release is the foundational learning principle underlying virtually all effective horsemanship regardless of discipline, methodology, or training philosophy. The concept is simple enough to state in a sentence: apply pressure to ask for a response, release the pressure the moment the correct response occurs. The horse learns not because the pressure tells him what to do, but because the release of pressure tells him that what he just did was correct. The pressure creates a search. The release identifies the answer. The mechanism by which pressure and release produces learning is rooted in the horse's fundamental nature as a flight animal. A horse's entire survival system is built around seeking relief from discomfort, and training systems that work with this instinct rather than against it produce horses that learn willingly and maintain their learning over time. The horse is not being forced to do anything — he is being given the opportunity to find the relief, and the finding is what produces the learning. The hierarchy of pressure is one of the most important practical principles. Always begin with the lightest possible pressure — lighter than you think is necessary — and escalate only if the horse does not respond within a reasonable time. The lightest pressure that produces the correct response is the one you want to use, because it preserves the horse's sensitivity and teaches him to respond to whispers rather than shouts. A rider who begins every request with strong pressure trains a horse that ignores light aids and requires constant escalation. The release must be immediate, complete, and consistent. Immediate means within a fraction of a second of the correct response. Complete means the pressure goes away entirely rather than being reduced to a lower level. Consistent means the same response to the same pressure always produces the release. Building the try is a concept within pressure and release where you release for progressively closer approximations of the full response — the first release comes for the smallest try. This building of the try produces a horse that is confident, willing, and actively engaged in the problem-solving process rather than one that shuts down from pressure that was too much too soon and never got released for smaller efforts along the way.