When you meet someone new in a perfect setting -- an attractive stranger at a close friend's wedding, say -- how much shared understanding can you automatically feel is there? What do those feelings do to you? For you? How do they bring about more actual shared understanding?
Is there some optimal mix of underlying similarities and differences to explore? Have you ever felt actually too similar to generate heated interest? Some dynamically creative tensions, some charged polarities are clearly optimal. But, I'm not sure those rely on any underlying differences -- maybe just on a tendency to take on different roles.
How much shared understanding is needed for maximal closeness, rapport, caring, love? Does closeness peak somewhere between The Royal Tenenbaums ("...we're just going to have to remain secretly in love with one another.") and The House of Yes? (Mmmmm.)