I knew with my son as soon as he could walk. We'd be walking in the mall and a pretty girl would come out of one of those boutiques. He'd pull his hand out of mine an toddle off after them, taking their hand if he caught up with them before I did. He was a total charmer. He's had this little trick from his earliest days: He'd take a girl's or a woman's hand, look them in the eye, and kiss their hand.
Equally, I've seen little boys punished for being "too sensitive" or told not to be "girly" by just about everyone. It's rediculous to think people make a choice to be ridiculed or demeaned like that.