I knew it. I posted about it a few months ago, when a Canadian psychologist suggesting that "letting your mind wander" (or a mind that wanders of its own accord) can be beneficial. Now a Dartmouth study says that daydreaming is beneficial because your mind may be working out issues that aren't immediately relevant, but that aren't entirely unimportant either. So there. Next time you see someone sitting at their staring out of a window, they're working on something. It just may not look like it.