I don't think learning the truth really affected my development one way or the other. One day when I was I-don't-remember-how-old, I asked to be told the truth and I was. I do remember that I wasn't very good at maintaining the conspiracy former my younger siblings, and almost let the truth slip a few times---and I'm still not very good at it and have almost let the truth slip to children in my family.

I am wary of whether lying to kids habitually is really as good for them as we rationalize, but the real reason I'm inclined not to spread this myth to my hypothetical children is because I am so uncomfortable with lies myself---I can barely even bring myself to do it for the sake of a surprise party or something innocuous like that. I'd rather tell it as what it is: a fun story, like Cinderella or Harry Potter.