Kit Kat has learned that if she wants to come out all she needs to do is still by her door and I'll come and open it. However, if I don't see her waiting or I can't get to her at that moment then she will chew on her bars. If she starts chewing I let her chew until she stops. Usually she only chews for 15 seconds and runs off to her top bin. Once she has stopped, I will wait about 15 seconds more and then I'll let her out.
I figure any attention from me while she's chewing is a reward for her. I don't give in to her chews and she knows it won't get her out. Best not to reward any bad behavior or they'll think that chewing is the key to getting out.
Kit Kat only has two bars she chews on and those are blocked of by clothes pins at night when I've gone to bed.
There are a lot of other bar chewing factors and they are all wonderfully highlighted by Vectis Hamstery. Well said!
