When I was late in school, I distinguished all the types of people in the world by their general manner and aspect of behavior. That is to say, I studied Psychology.
And I propounded theories. One of my theories divided all people into two groups, grinners and non-grinners. Regardless of language or culture, if you look at a grinner, he or she will always grin. They grin all the time, at everything. Even when nothing is funny. Non-grinners never grin. Even when something is really funny.
It's not hereditary. Both my parents were grinners, but I am not. My wife is not a grinner, either. Only after a moment of sober and strategic reflection, will we react to your entreaty.
In this way, you can evaluate the people you meet.
Katie Couric is a grinner. Bernanke is not. And so on.
I'm working on an application for the G-Phone. You hold the phone up to somebody and it will tell you if they're a grinner or a non-grinner.
It should come in handy.