I've noticed something interesting lately -- lately here means since March 2010, but, yeah. And this is by no means a conclusion. It is based solely on my observations in a few classes and my interactions with male and female students.
When female students talk, they tend to say "I think" or "I feel" or "I may be wrong, but ..." or "In my opinion" quite frequently throughout their speech. The males rarely do this. It's as though the former are unsure of their statements or knowledge, while the latter display more confidence. Why do you think this is?
Reminds me of the lovely advice that many graduate student friends gave me when I was writing my grad school proposals: "Why be afraid of what you've accomplished? Write like you've already been accepted there, but it's just a matter of their realizing it! Make it appear to mean, 'You've already accepted me, but I'm just reminding you why.'" It helped a lot, I have to admit, and it's the advice I'd give to every other student as well -- but, of course, that requires knowing well the difference between being arrogant and being confident.
Anyway, so, yeah. Next time there are presentations in your class(es), compare the way the men carry themselves to the way women do. Fascinating stuff, no? ('Course, I'll be pleased, if surprised, to hear that this is generally not the case according to another person's observations.)