I was going to put forward some ideas around money in relationships, who's money is for spending, who's is for saving and who's is for entertainment. However, I think a Nature vs. Nurture is a bit more interesting point.
When I say , testosterone, images of aggro over-sized men are usually the mental images that form. Possibly even a brutish Neanderthal, then some of the after thoughts include the effects on a man's physical (thoughts: "men have needs, sometimes we think with our needs", lol) and the mental aftermath. The bottom line as most people know (but never fully accept), is that men are sexual. It is a hardwiring written across all the species, one of the primary drivers for evolution itself. We are nurtured into repressing this drive, granted, we shouldn't be running up and down the road advertising our desires. There is however, this teaching that men should curb their desires and control themselves. To control what their bodies and their nature that is driving them to be as such.
The only reading I ever found of a woman trying to explain this was, "consider those days when you really want that piece of chocolate or cake and are ready to move heaven and earth to get to it". That's men's drive.
Oestrogen, the maternal, care givers hormone that is credited with the continuation of intellectual development of the species(through its primary host). Men know this hormone well, it's dark side. A compound that can, by simply being there, can make your mild mannered partner put The Incredible Hulk to shame. I would like to reestablish that hormones can have very extreme effects on women, their physical and mental states. As a society, we have come together in support for women and the aftermath of their hormones, created a reassuring cocoon where we let women know that "it's okay. You were very emotional, your hormones are all over the place, this isn't really you". Men have even learnt various responses to the signs that this hormone is in effect, we don't always get it right, but we learnt.
Two hormones with incredible power over the body and mind, but one is not as well supported. In fact, to try and encourage control over the effects of female hormones is often labelled as "insensitive". I'm not encouraging philandering by men. Just the acceptance that our hormone is built around sexual gratification and is often associated with aggression. We get very testy, excuse the pun, when are driven by this hormone.
Of course, there are those who will see this as a bit of whining and you have all the right to believe so. All I'm saying is that, there are no "T&C 's Apply" with today's fifty-fifty model. "I understand, but..." is not understanding (that goes both ways).