https://youtu.be/00w1HGqyxTM

The 'unpredictable' part made me think of what I and some others have discussed about horses. One lady said there are A student horses, B's, C's, etc. I've ridden some of each type, but I would never ever again work with anything less than an A student horse. They're unpredictable in the sense that they're so smart they can do things that seem very confounding till you figure out what they're actually telling you, and when you do figure it out you have another picture of just how smart that horse is.