How do I get my horse comfortable with flags, tarps, and plastic bags?

Flags, tarps, and plastic bags share a common characteristic that makes them alarming to horses: they move unpredictably, make noise, and look unlike anything the horse encounters in a natural environment. The horse's visual system is highly sensitive to movement at the periphery, and objects that flap or billow trigger the flight response reliably in horses that have not been exposed to them. Desensitization to these objects follows the same progressive approach: introduce the object at a distance where the horse shows awareness but not panic, allow it to habituate at that distance until genuinely relaxed, then decrease the distance incrementally. A plastic bag on a fence post fifty feet away is a very different stimulus than the same bag being waved near the horse's head, and the progression from one to the other should take as many sessions as the horse requires — not as few as the handler wants. For tarps specifically, begin with the tarp flat on the ground at a distance the horse can approach on its own timeline. Allow the horse to sniff and investigate before asking it to step on or near the tarp. The sound of the tarp moving underfoot surprises many horses even after they have accepted the visual; expect a brief reaction and reward the recovery. Flags used in desensitization work are most effective when the handler controls the flag's movement — hold it still when the horse is tense, move it gently when the horse is relaxed — so the horse learns that its own relaxation controls the stimulus.