What causes a horse to jig and what is the correct way to fix it according to Clinton Anderson?

Jigging — the tense, choppy, half-trot that a horse performs instead of walking when it is anxious or anticipating — is one of the most common and most frustrating under-saddle problems because it is exhausting for the rider and tends to feed itself: the more anxious the horse becomes, the more it jigs, and the more it jigs, the more the rider tenses, which feeds the horse's anxiety. Clinton Anderson's diagnosis of jigging is consistent: it is almost always an energy management and leadership problem. The horse has more energy than it has direction for, combined with insufficient respect for the rider's decision about gait. The horse that jigs is essentially overriding the rider's walk request with its own preference for faster movement — a leadership dynamic that Anderson addresses directly. His correction method works on several levels simultaneously. When the horse jigs, Anderson does not pull back with both reins to slow it — pulling back with both reins gives the horse something to push against and confirms that forward energy is acceptable. Instead, he picks up one rein and puts the horse into a tight circle, making the jigging direction — forward — into work. The horse is trotted in circles until Anderson asks it to walk again. If it jigs again, it goes back on the circle. Over repetitions, the horse learns that jigging leads immediately to more work and that walking is where rest is. Anderson notes that horses with well-established jigging habits may require many sessions of this correction before the walk becomes their default response, and that inconsistency — sometimes allowing the jig and sometimes correcting it — makes the problem significantly worse. Warwick Schiller addresses jigging from a nervous system perspective as well, noting that horses that jig chronically are often horses with elevated baseline anxiety, and that addressing the relationship and confidence work outside of riding sessions reduces the baseline that produces the jig in the first place.