Quite possibly. I remember reading somewhere that research has shown that men tend to exhibit more exceptionalism at both ends of the spectrum and in almost all things. For instance, height varies much more in men than women. Behavioural characteristics too. More men are very unintelligent and more men are very intelligent than appears to be the case for women. Women tend towards greater homogeneity than men.
I just think girls are better at hiding it.
Yes and yes.
I really believe that stupidity does not discriminate against specific genders.
I think with men its a vascular problem... the blood flow is often diverted or something like that.