Without a doubt it's Gender Relations.
I've always been fascinated by people's relationship choices. Why do you say yes to one person and no to another? Why do you choose to stay in a relationship where you're unhappy? Why would someone rather try and (change) their mate over trying to find someone who (already is) the type of person they want?
Very few choices rise to the level of importance as selecting one's life partner, and yet many of us never take the time to do the necessary introspective thinking needed to determine what it is we want and need from a mate or potential spouse. It's almost as if making relationship decisions with complete awareness and self-empowerment is "unromantic" or "anti-American".
We prefer to have relationships come about through "happenstance" and when things go wrong we want to point the finger at our exes!
If you go to the store to purchase an apple but buy an onion instead....Whose fault is that? Do you curse the onion for not being an apple? No! You learn to become a better shopper!
I was so interested in how people approached relationships and marriage that I wrote a book: My Cat Won't Bark! (A Relationship Epiphany) I find people's relationship choices to be especially interesting.