Well, Stephenie said this about that in the Personal Correspondance #10 that she had with the Twilight Lexicon:
"What Jasper does effects not the thoughts, but the body. He doesn’t make you THINK you are calm, he actually puts your body into a calmed state. Or angry, or whatever. It’s physical rather than mental."
If you think about it you can kind of see that in Twilight when they are in the hotel room. Yeah, she feels calm but her thoughts are still troubled and it feels weird to her that her body feels one way and her mind another --or I guess that's just how I saw it.
@jessica-No I cud of sworn she actually got upset wen jasper was controllin her emotions at 1 point but she cudnt snap outa it. I think it was in New Moon.
@ashleigh- emotions r mental lol. Deyr not physical
If it is specifically mental, how is she able to shield others such as Jane, Alec, and other powers with physical affects?
Emmelie Cullen Black said:
Somebody in the series already explained that point. I think it was Alice or Edward. Ok it's kinda like this: Edward or Aro can't acess Bella's mind cuz' their powers work mentally and Jasper's powers work emmotionally. So basically, Edward or Aro can only work from people's minds and that is where Bella's power resides, but Jasper's power is able to work with emmotions that come from the heart. So is power is not mental, it's emmotional. So that's why Bella's shield doesn't work with Jasper's power.
Emmotions are physical and her shield is mental.