Interesting, isn't it? I was always told that we want certainty—that uncertainty was intolerable to us; we want to be in control. But, when I stop to think about it, he's correct. Mind the caveat, though, "provided we can keep it under control and clear of confusion."
Now, transpose that to children. We don't need to motivate them to learn. They want to learn. We just need to keep from destroying that desire—not an easy task in the classroom, is it? I am extremely thankful that I read many of the required texts in high school before I took the classes. I would never have liked the books if that were my first exposure to them! Isn't that a sad commentary?