If you’re the kind of animal that uses fine, subtle cues to communicate, what would you think if you saw a raging bull charging right at you? A well-recognized “problem” with bull-fighting horses is their inherent flight reaction—get away from the oncoming threat. The “solution” to that problem in some cultures raises red flags with animal protection associations: a blindfold.

For years, horses participating in traditional Spanish bull fighting have been equipped not only with blindfolds, but also with ear plugs and chemicals in their nostrils to block out the bull’s smell. The result, some international welfare organizations say, is a horse with blocked senses in a vulnerable position.

“The horses in the first phase of a corrida (bull fight) are used … to get the bullfighters high enough to stab the bull in the back of the neck to get its head to drop,” said Roger Lahana, vice president of the Anti-Corrida Coalition in France. “The bull … targets his revenge against the unsuspecting horse and charges it, again and again. With his senses blocked, the horse knows it’s being hit by a strong force, but it doesn’t know what it is or where it’s coming from.”

While researchers have yet to study the scientific effects of blindfolding in corridas, they do have theories about sense-blocking. “When you want to force a horse—or anyone, really—to do something that they don’t want to do, the first thing you do is cut off all their links with their environment,” said Paolo Baragli, PhD, researcher at the University of Pisa, in Italy. “That’s exactly what’s going on when you block out hearing, vision, and smell from horses in the presence of bulls