What is the function of the bit in a bridle?

The bit in a bridle serves primarily as a tool for communication between the rider and the horse. It achieves this by exerting pressure on the horse's mouth, allowing the rider to convey various signals and cues essential for guiding and controlling the horse during rides. This communication relies on the sensitivity of the horse's mouth; when the rider pulls on the reins, the bit applies pressure at specific points, which the horse learns to interpret in different ways.

While other options touch on important aspects of equestrian equipment — such as adjusting speed or holding the reins — they do not accurately describe the primary role of the bit. A bit does not directly adjust speed; instead, speed adjustments come from the rider's overall aids and commands. Comfort can be influenced by the choice of bit and its fit, but that is more about how it is used rather than its fundamental function. Lastly, while the bit helps to keep the reins securely in place, that is not its main purpose, which is to enable precise communication between horse and rider through the pressure applied in the horse's mouth.