I was interested in learning more about how young and troubled children perceive things and before filming started I showed some paintings to the children. 
The results were very revealing and mysterious. I remember one, an Italian renaissance painting which had in the background an entire city with castles and harbours and hundreds of people weaseling around unloading ships, all sorts of things going on. I would project a slide of the picture for maybe ten seconds and then turn it off and ask the children, “What have you seen?” And four or five of them in one voice shouted, “A horse! A horse!” “Where on earth is the horse?” I said to myself. So I put the slide back on and searched. “Down there!” they all shouted. And yes, in the corner of the picture was a single horse and a single horseman with a lance. It makes me think to this very day.
—Werner Herzog, Herzog On Herzog
How did you find out this fact? I am a fan of Warners works. Thanks for this interesting fact. I do see the horse!!!
The quote comes from a book called Herzog on Herzog, which is sort of one long interview with him, about his life and films through 2001.