If you are going to be teaching video in any of your classes this year, you might be interested in this article on Roger Ebert’s blog:

“How to read a movie”

Now what do I mean by "positive" or "negative?" I mean that these are tendencies within the composition. They are not absolutes. But in general terms, in a two-shot, the person on the right will "seem" dominant over the person on the left. Does this apply even to films from cultures that read right to left or top to bottom? From my treks through many Asian films, yes, it seems to.