I spoke with a student this about the evolution of riding. We first teach kids to be still on the horse. Kids often start out as too busy on their horse’s back. It gives the horse a lot of mixed signals. The horse has to choose to ignore the busyness or get anxious.  In my case I rode equitation which required us to sit like statues on our horses. We go from too busy to too stiff. What we need is right in the middle.  The middle is where we learn to feel the horse’s movement