Is this actually possible?

I forget was this is called, but it's a type of writing exercise where you just scribble on a piece of paper and try to let your subconscious take over or something like that until you start writing words without meaning to. It was in the movie the Sixth Sense, the kid did some of this type of writing, only his was all creepy stuff about ghosts. I was wondering if people have actually tried this or heard of it and if it ever works, and if so did the words written make any sense? I just think it'd be a cool thing to try, but I have no idea how to do it. I tried it and ended up with a piece of paper almost black with scribbles - lol, unless they were really a bunch of 'O's and my subconscious was saying, "Ooooo. . ."