Desensitizing a yearling to ropes, tarps, plastic bags, flags, and other objects that it might find alarming is one of the most important investments in the horse's long-term safety and trainability. A yearling that has been systematically exposed to a wide range of stimuli and learned to remain calm through them develops a generalized confidence and resilience that transfers to new scary situations it encounters throughout its life — the brain learns that novel, alarming things are not actually dangerous, and the threshold for flight responses rises accordingly.
The process follows a consistent pattern regardless of which specific object is being introduced. Begin at a distance that the yearling can observe the object without showing significant alarm — ears pricked and alert is fine, spinning and bolting is too close. From that distance, allow the yearling to habituate to the sight of the object while remaining calm. Then move progressively closer as the yearling shows relaxation, never advancing when the horse is showing significant alarm.
Ropes draped over the back, legs, and neck desensitize the yearling to the sensation of things touching it all over — directly relevant to future saddling and riding preparation. Tarps on the ground teach the yearling to step on and across unfamiliar surfaces. Plastic bags on a stick allow the handler to control the intensity of the stimulus and to use approach and retreat — increasing and decreasing the stimulus based on the horse's response — to build confidence systematically.
Warwick Schiller's approach emphasizes allowing the horse to investigate scary objects on its own terms rather than forcing approach, which builds genuine confidence rather than learned helplessness. A yearling that walks up and sniffs a tarp that previously alarmed it has genuinely conquered that fear. A yearling that was forced to stand next to it while trembling has only learned that it cannot escape.