<p>I also have a dog who goes and sits quietly at the door. When he was a puppy we gave him a dog biscuit every time he made a successful trip outdoors. As soon as he figured this out, he would wait patiently at the door with no accidents since he knew a treat was riding on it.<br>
Now that he is a mature big boy (75 lbs.) he goes for hours without going to the door to be let out but he still looks for the treat afterwards.</p>