Why does my reining horse turn before I ask?

A reining horse that turns before being asked — beginning a spin, initiating a rollback direction, or drifting into a turn without the rider's specific cue — is anticipating a maneuver that its training has associated with a specific context or location, and it has begun executing that maneuver from the environmental cue rather than from the rider's intentional aid. This is the spin or rollback equivalent of stop anticipation: the horse has mapped the pattern well enough to predict what comes next and is acting on that prediction rather than waiting for the instruction. For a beginning rider, a horse that self-initiates turns is particularly challenging because the beginner may not yet have the positional stability or independent leg to correct the turn once it begins, and may inadvertently reinforce the anticipation by allowing the turns to continue when they start. The correction requires disrupting the pattern at the point before the anticipated turn begins. If the horse turns into a spin whenever the rider slows near the center of the arena, deliberately slow near the center and continue on a straight line or circle rather than spinning. If the horse initiates a rollback turn direction whenever the rider stops on a certain side of the arena, stop in that location and stand, back, or walk forward rather than rolling back. The horse must encounter the anticipation trigger — the location, the speed, the pattern element that precedes the turn — without the anticipated maneuver following it enough times that the predictive association breaks down. A trainer who can observe when and where the anticipation occurs can identify the specific trigger and recommend the specific variations that will most efficiently disrupt the pattern.