Human babies are clearly not born knowing whether/how to hold in urine and feces, and teaching them to do so requires a nontrivial (really nontrivial...) amount of work on the parents' part. But once this skill is learned, it becomes so effortless that one does it automatically in one's sleep. I can't think of any other learned behaviors that are either (a) performed while unconscious, or (b) controlled by the parasympathetic nervous system, both of which are true for excretory control. The fact that, once learned, excretory control becomes so "automatic" seems to suggest to me that it's not entirely a learned behavior. If no one ever actively taught a baby to control its bladder and bowels, would it eventually learn to do so on its own (suggesting that excretory control is actually an instinctive rather than learned behavior)? Presumably this experiment has never been performed on a human baby, but are non-human animals born knowing how to control their bladder and bowels, or is this a learned behavior?