One of the weirder things about the news stories following James Corden's debut as a US chat-show host earlier this year (apart from the fact that it was news at all) was the list of things that American audiences found unusual about the History Boy's technique; the studied informality, the fact that he put his guests on a sofa rather than chairs, encouraging them to interact rather than go off on one and, above all, the fact that he sat to the left of his guests rather than to the right.
To anyone who knows Robert McKee's Story; this isn't a great surprise. McKee devotes a section of his book, and the seminar from which it derives, talking about what he terms Screen Dynamics. Studies have been done showing that, as cinema (and television) audiences, we don't spend equal amounts of time looking at all of the screen. The eye describes a sort of perpetual oval, starting in the top left hand corner, travelling right, down, left and up, before starting all over again. The second half of this journey is quicker than the first, so that the right-hand side of the screen (as you look at it) is the one that gets more than its fair share of attention.
McKee argues that good film directors and cinematographers have always known this, and brings it into his analysis of Casablanca, in which Michael Curtiz almost always places Ingrid Bergman on the stronger, right-hand, side of the screen, even when it means giving Humphrey Bogart an inappropriately right-hand drive car in the French-set flashback scenes. Corden, in sitting on the left, is playing low-status, giving his guests the stronger postion. In this respect, he's following a more British tradition of the chat-show host as vehicle, rather than star - Michael Parkinson sat on the left, Johnny Carson on the right.
It's debatable whether all this is hard-wired or culturally determined, and whether it works the same way in other cultures, especially those where script is written in a different configuration, as in Arabic or Japanese. Roman Polanski believed that habits of writing affected the way in which we interpret motion on screen, telling Ken Tynan on the set on Macbeth that 'To the Western eye easy or successful movement is left to right, difficult or failed movement is right to left.' (The Sound of Two Hands Clapping, p. 101).
Once you've been told about this, it becomes almost impossible not to start seeing it in action. For instance, when Scarlett Johanssen and Bill Murray are onscreen together in Lost in Translation, Sofia Coppola almost always gives Murray the stronger, right-hand position. (The only shot in which this isn't the case, at least for a sustained period, is the one used as the film's poster. Make of that what you will.) It's tempting to suspect that Murray's star power was a factor here, but it's more likely that Coppola, as visually aware a director as any, realised that the screen would balance better if the weaker position were occupied by the younger, and more visually striking, of the two. (And yes, I write that as a male heterosexual, but still.) Indeed, when creating a shot with two people, it could be considered a film-maker's convention that the image balances better if the more physically attractive person is on the left. If I was from a naval background, I'd call it the Fair/Port Convention. (Start the car.)
It's also difficult to say to what extent it's also true of the theatre - stages have their own dynamics and hotspots, to do with architecture, so it's harder to generalise about them than cinema screens. There also may be other factors; I remember being surprised that Richard Olivier, directing the Globe theatre's inaugural production of Henry V, had staged the final negotiation scene with the victorious English, and Mark Rylance's Henry, on the right. Most productions that I'd seen - Laurence Olivier and Kenneth Branagh on screen, Michael Bogdanov on stage - do it the other way round, magnanimously giving the stronger position to the defeated French. After a while, I realised (or at least, guessed) why this production bucked the trend. Charismatic and talented actor that he is, Mark Rylance isn't obvious casting as Henry - to put it bluntly, he's quite short. Sometimes, an actor can use all the help he can get.