At a regional show jumping event, a young rider and her pretty dapple gray enter the course and head for the first fence. Clear. Second fence, clear. Third, an oxer, clear. Then the fourth, a water jump, and whoops! The rider’s down. But what about that lovely dapple gray? Does he stop and wait for his slightly disoriented human? Not this guy. He just keeps going on without her, to the fifth, sixth, seventh, eighth … in whatever order seems right to him.

Why do some horses do this? Or why do racehorses keep running a race (sometimes winning it) even after they’ve left their jockey 800 meters back?

One simple word, say a French equine behaviorist: automatism.

Automatism is the curious brain function that makes us perform actions without even realizing it. It’s automatism that makes us instinctively apply an aid to our horses just at the thought of turning or stopping. And it’s automatism that makes these sport horses keep doing what they’ve been trained to do, even if they’re no longer getting the aids or rewards to do them