How Do They Learn This Stuff?

These sweet little girls are my neighbors.  I took them out for an impromptu shoot tonight because I couldn't resist the natural light.  Perfect!  My question is How do they learn how to pose like this at such a young age?  Aspen is truly a natural and I'd definitely use her as a model again.  She wasn't afraid or intimidated by me or the camera at all!  LOVE IT!