I had an unusual, and enjoyable, invitation last month, to speak on the Paula Principle - to a conference on chess and female empowerment. The primary focus was on encouraging girls not just to start playing chess but to continue after the age of 11. Until that age there are as many girls as boys playing, but apparently there is a very steep drop-off as they enter puberty. Why? Of course in part it's because girls find other things to interest them. I assumed the main reason was that they dislike the individual aggression, the hand-to-hand combat of chess. Well, we were told that girls are just as competitive. But…