Celebutopia has an interview with Jackson Rathbone and here is part of the interview where Jackson talks about his character Jasper:
TeenMag recently asked Jackson why Jasper’s vampire abilities weren’t mentioned in Twilight.
Jackson answered: “Well it doesn’t really come out too much in the book. It’s one of those things were it’s understood but in the third book it really comes out like the back story and everything.”
“I think one of the things we didn’t want to get too much into was focusing on all the other vampires.”
“We wanted really to establish this relationship and how she (Bella) gets sucked into the world of the Cullen family and once she’s in the world that’s when things kind of start coming out.”
You can read the full interview HERE