I don't recall "Drawing on the Right Side of the Brain" relying much on psychology, though I readily admit I haven't read the intro in awhile. The lessons within the book rely mainly utilizing our creative thinking processes as opposed to analytical thinking. For instance, thinking about shapes of light and dark instead what an object is. The object is accurately rendered because the placement of light and dark shapes is correct. Maybe an over-simplistic description, but the gist is I don't think think there is much reliance on being preached to about psychological theory like we might find in many self-help books. Like anything, take what you may find valuable and leave the rest. Or you may find it all not to your liking in which case that's fine too.