My terrier Bobbie knows how to play fetch but does not see the sense in it. Sh will go for the ball grab it and than chew on it or whatever. If we ask her to bring it back, she just kind of looks at us like "yeah, I just ran all the way over here to get this ball and you expect me to go back to you so you can take it away and throw it again, I don't think so"

She is just to smart. Our lab on the other hand loves to play fetch and he was never trained to do it he just did it naturally.