What does licking and chewing mean in a horse during training?

Licking and chewing — the opening and closing of the mouth, movement of the tongue, and sometimes audible smacking that horses show in non-eating contexts during training — is one of the most widely discussed and most frequently misunderstood behavioral signals in natural horsemanship, and understanding what it actually indicates requires distinguishing its genuine meaning from the simplified interpretation that early natural horsemanship teaching sometimes promoted. In Monty Roberts's join-up teaching and in early natural horsemanship literature, licking and chewing was described as a sign that the horse was accepting the trainer's leadership and shifting from a defensive to a receptive state — a specific signal of the horse's decision to accept the relationship being offered. This interpretation contains genuine insight but has been refined by subsequent behavioral research that suggests licking and chewing is more accurately understood as a sign of nervous system transition — specifically, the transition from sympathetic nervous system dominance, associated with the flight-or-fight arousal state, toward parasympathetic nervous system dominance, associated with the relaxation and digestion state that is sometimes called rest and digest. This means licking and chewing indicates that the horse's arousal is reducing — that the nervous system is moving toward a calmer state — which is consistent with the join-up interpretation but more precise in its mechanism. The practical training implication is significant: licking and chewing is a signal that the horse has just experienced a significant shift in arousal level, suggesting that the training interaction at that moment produced a genuine change in the horse's state rather than simply a behavioral response under continued pressure. Warwick Schiller has emphasized that the moment of licking and chewing is a moment to pause and allow the horse to fully process the state transition rather than immediately moving to the next training demand, because the processing that the licking and chewing indicates is itself part of the learning.