I learned a good lesson this evening while doing desensitization exercises with a plastic bag on a stick. Even though you think you may be teaching the horse one thing, he may be learning something completely different. Here's what happened.
I first had Bombay follow the plastic bag by leading him with a rope halter and lead rope while walking backwards and holding the bag on the end of the stick out toward him. He had no problem with that. Then I waved the bag in the air while having him follow it. Still no problems. Then I shook and rattled the bag while having him follow it. So far, so good.
Then I held the bag close to his face, and when he reached out with his nose to touch it, I took it away to take the pressure off and reward him for trying and being brave. First I did this straight on, then to the left side of his face, then to the right side of his face. Each time he poked the bag with his nose, I took it away.
I could just see the wheels turning in his head as he thought he was scaring the bag away by touching it. "Good," I thought, "he's feeling more confident and powerful."
But then it occurred to me that at the same time that he was poking the bag with his nose, he was also snorting. Could I be teaching him to snort?
Sure enough, when I stepped it up a notch and tried to touch his body with the bag, he pulled back, ran in circles and snorted up a storm. I made him stop and face the bag, and he frantically kept poking it with his nose, snorting louder and louder. I knew I couldn't take the bag away at that point, but had to wait for signs of relaxation, since rewarding him for "trying" was turning into rewarding him for snorting.
When I didn't remove the bag during all that snorting, he looked at me for hints. He slowly began snorting quieter and quieter, and I slowly began moving the bag further away from him. Soon he learned to poke the bag with his nose minus the snorts. By the end of the lesson he was letting me shake the bag all around his head in the air while he stood quietly. After that I was more careful about only rewarding him for signs of relaxation as opposed to trying.