Little Hawk makes some interesting points. Children have to be taught the formalities of atheism or religion. However I think they are almost natural mystics and are highly superstitious little creatures - some more than others of course and it usually fades with age, as outside influences inform beliefs about such things. All kinds of taboos and magical ideas permeate kids minds, and they mostly arise from within not without, that's why they generally don't share them with adults who categorise them either as childish imaginings (atheist parents) or evil ones (religious parents). Be they the very real friend that no-one else can see or hear, or the knowledge that they used to have another family, or that the old tree houses a malevolent spirit.