Exposing the belly is definately a sign of feeling completely secure and trusting. My Bo is absolutely irresistable when he goes belly up - which is often, so he gets lots of rubs. One day I decided to keep track of how many belly rubs Bo asked for - he got 14! From the look of contentment on his face and the roar of his purr, it must be absolute heaven. I sure wish I had someone to give me some sugar like that! LOL!