How does the rider's hand position affect neck rein response and what is the correct position?

Hand position in neck reining is a detail that directly affects how clearly the rein communicates to the horse, and Clinton Anderson addresses it because many riders inadvertently make the neck rein harder for the horse to read through incorrect hand position. Anderson teaches that the rein hand in one-handed western riding should be held low — approximately at or slightly above the horn height — with the wrist flat or slightly bent downward, not cupped upward. A hand held high pulls the bit upward in the horse's mouth rather than backward, which changes the bit's action and confuses the communication. A hand held low maintains the correct bit angle and keeps the rein in the plane where its lateral movement against the neck is clearest. The hand should be positioned over the horse's neck, roughly above the mane, not out to one side. A hand that drifts to the right is already applying right rein contact before any deliberate signal is given, which desensitizes the horse to the right side of the neck and makes the rein communication on that side unclear. Centering the hand gives each lateral movement — left or right — equal meaning and equal clarity. Parelli adds the observation that the rider's wrist rotation is the primary mechanism of the neck rein signal — rotating the wrist left moves the rein against the left side of the neck to signal right, and rotating right signals left. This is a subtler signal than swinging the entire arm, which is the error many beginning one-handed riders make. The more the arm swings, the coarser the communication. The more the signal comes from wrist rotation with a still arm, the more refined the communication becomes over time.