If an eleven-year-old were to become immortal would they still mentally mature? I suppose this might be more a neurological question than anything. If someone's body and brain were to stop developing at a young age but they were still able to learn and observe things, would they mature? Or would they just be a really smart kid? The only example I can really think of is Claudia from Interview with the Vampire and her whole problem was her brain being older than her body.