Most Python Regius that I have seen are head shy. Of my 2, the female is slowly growing out of it. When I first got her she would jerk back from anything that came close to her head. Now I can pet the top of her head and she doesn't mind to much (she still jerks back every once in while). My male is a whole different story, every time I try to pet his head (or mist him during shed) he jerks back insanely quick and balls up. One reason I can guess is becuase when they feel something touching their head, they feel threatened and react by jerking back, balling up, or biting.