I'm just waiting for someone to quote John Grey (Men are from Mars...) on this horribly drifted thread, which started off with a bloke being thoughtful and saying thank you and then was hijacked by some people with an axe to grind.
The attitudes of some of the female posters here are unbelievable, I work in a female oriented environment, where there is no gender advantage and am used to working in equal partnerships.
I have to say that if confronted by some of the attitudes here, I would find it totally tiresome and would not accept such whinging - I know the women I work with would not take it, either.
As for conditioning, Mary do you mind me asking (respectfully) what knowledge you have in the area of psychology? Confidence is not built by conditioning (in the traditional sense), as the purpose is to train someone to react in a certain way to a certain stimulus. Of course, confidence in the new ability may develop as a consequence.
Having said that, personality and motivation equally have a part to play, as does culture.
I would say that younger men typically (but not always) display more bravado and younger women typically (but not always) tend to be a little more cautious, but that is a different set of labels to confident/under confident.
The women I work with are highly confident professionals, built on years of professional development.