Yeah, I am thinking that temperament might even be genetic. I read on a rat breeding site that it was, and I am inclined to believe it. This is because I have one daughter of one of my "evil" females, that is still evil, even though I tried since birth to handle her. She was always jetting away frrom me as soon as I put my hand in her cage! But this new female is not at all afraid. Unbelievable.