What we know about the world and its opportunities limits what we do. If we do not know that there is a pot of gold at the end of the rainbow, we will not follow it. If we do not know that a desert cactus contains water, we will not cut into it for sustenance. Often, however, we do know things about the world and yet the knowledge does not seem to be reflected in behavior. Explaining this fact simply in terms of inadequate motivation for expression...