I thought I had a stupid Yorkie once, but she proved me wrong.
I honestly haven't had one really stupid. Stubborn yes but not really dumb.
I think they give you what you put in and expect from them. The one I thought was stupid was really just sucking up to her daddy and it worked every time.
I guess I am going to have to shake them and see if I hear more than 1 marble in there. LOL