I remember seeing something where one of the differences between the female brain and the male brain, is that the female brain is securely and heavily circuited to activate reward chemicals upon doing something "nice" for someone. Why does this matter? Well, I also remember seeing that the male brain isn't circuited to expect reward upon doing something out of empathy near as much. Meaning for women, there's a psychological system implanted to do a favor, and immediately expect a reward for doing so. Funny, how they'll all preach about empathy and doing things for people out of the goodness of your heart and self sacrifice, when in their world it's only feasible because they're ALWAYS rewarded for doing so. Of course with any relationship there's a give and take dynamic, but for women it seems that dynamic is bothersome if they're not receiving more in return than what they gave. The male will do something truly out of empathy because he cares, not because he wants something back for it. And I've witnessed those differences many times socially.