Every time you see Willow's nose touch me, she's executing tiny "bites" in rapid succession. She can do a hundred of these little light bites in one play session. Willow, very unsocialized (she lived almost all of her 2 years alone, and with no human touch), is faux biting me. I had one other rat, Dicey, who was originally very aggressive, do this same behavior as she turned friendly. The first time it happened, I was uncertain as to the meaning. I stopped in place and waited until Dicey finished and pulled back. Then I slowly began to pull out of the box my hand was in, thinking she didn't want me there. "Oh no no NO" she said, as she grabbed my hand and dragged me back inside, where we repeated the "biting" play a few more times. It's a pleasure to let a rat treat my skin like she would do with a buddy rat. I encourage this kind of good teeth activity. More on that subject can be found here: http://www.joinrats.com/EarningTrust/RatsUsingTeeth/15630450_hH8bsw.