When riding a horse, the rider communicates high-level information (e.g., the goal) to thehorse but must be ready to guide the horse at a lower level. When the horse knows what to do,for example, if the route is familiar, the rider may not need to engage in low-level control. Thisform of control, called loose rein control, is possible if the horse knows what the rider wants.

The H-metaphor is a metaphor for understanding shared control [246]. Here, the “H” standsfor “horse”: the horse metaphor. In short, it means that shared control is like riding a horse.