At the bottom of each dressage test are collective scores called Gaits, Submission, Impulsion and Rider. All of these scores are doubled and are very important to the outcome of the riders overall score. Each of these aspects is evaluated in every movement of the test.
Submission is defined in the USDF Glossary as “Copliance and throughness. The yielding of the horse’s will to that of the rider, as revealed by a constant attention, williness and confidence in the attitude of the horse, as well as by the harmony and ease displayed in the correct exeution of the movements, including the correct bend, acceptance of and obedience to the rider’s influences, and a balance appropriate to the level and task at hand.”
In other words, everything from the shoulder up shows if a horse is being submissive. Thus, if there is tension in the bridle with the horse grinding his teeth, or resisting the connection, the scores will be very low. You want to have a soft neck and elastic connection to the bridle for the horse to be submissive and to achieve high scores. Obviously a submissive horse will receive higher scores across the board as it is considered in each individual score.