I've noticed this a lot in high school and college.. not very much among mature women.. she isn't wearing a belt or a long enough shirt and sits down, you see the upper part of her panties exposed from behind. I've always wanted to think they secretly wish to get the attention of other guys without making it too direct.. and those much older have stopped b/c they've gotten tired of getting too much attention perhaps. I'll admit, I've been turned on and ended up approaching a few girls whom I'd rate as 4-5 out of 10 before taking in a slight peak of their undergarments. Any ideas?