Interesting question! Whenever I see my cat on the couch or on a chair, I always just try to sit down with her (because I am desperate for her affection), but usually when I do, she is the one to get down and out of the way, even if there's plenty of room for the both of us! She is not fond of sharing.
It's funny, because my dad's dogs always sit on their couch, and when my dad and stepmom are going to sit down to watch television, they always ask the dogs to move, as though the dogs know what they're talking about. They'll be like, "Come on, Molly, I want to sit there." Needless to say, they usually end up pushing them out of the way. xD
