Going Into the Bag

Ever notice that a cat will, without much trepidation or pause, get inside a paper bag left on the floor? If there was one big enough, I'd probably do the same. What is it about a paper bag that changes things? The darkness? The brown, papery smell? The frank ending, after crawling inside, that causes one to back out again...or the only other option, to turn around and peer out of your bag? Either way, I am sure they're onto something.