How do you desensitize a horse to flags and plastic bags — two of the most common trail and show spook triggers?

Flags and plastic bags are among the most commonly encountered spook triggers for horses in both show and trail environments, and Clinton Anderson addresses both directly in his training program because they appear in so many practical contexts — parade routes, showgrounds, trailheads, and roadsides. For plastic bags, Anderson begins with a bag that is not moving and not making noise — simply holding a folded bag near the horse and allowing it to investigate. Once the horse sniffs the bag without concern, he allows the bag to unfold slowly, still not creating noise. As the horse accepts each level of visual change, he introduces slight movement, then more active movement, then the crinkle sound by handling the bag more energetically. The sequence always follows the horse's relaxation — no next step until the current step produces genuine indifference. For flags — whether a show flag, a safety flag, or a flag on a flagpole snapping in wind — the desensitization sequence addresses three separate components: the visual of something moving above and beside the horse, the snap and flutter sound, and the pressure of the flag touching the horse's body. Anderson works each component progressively, beginning with a still flag held at a distance, moving to a waving flag at distance, then waving it closer, and finally touching the horse with the flag on areas it is most comfortable with before moving to more sensitive areas. Warwick Schiller adds the environmental generalization point: a horse desensitized to a flag in its home arena may react to the same flag at a show because the overall activation level at the show is higher, reducing the horse's tolerance threshold. He recommends practicing flag desensitization in multiple environments, including environments where the horse is already somewhat elevated, to build genuine robustness rather than context-specific tolerance.