Well if you are female you are more likely to agree with the emotional aspects and if you are male with the physical aspects. Nothing new here. however if you are in a stable relationship, the differences tend to disappear. This is supposedly a counter-intuitive finding. But is it really? If you take an evolutionary perspective, males want to reproduce with as many females as they can while investing the smaller amount of resources in the offspring as possible, whereas females while more choosy, once they decide on a suitable mate will also want to want to reproduce as much as possible. It's in the initial choosing where the differences occur, after that it's all gravy. It's definitely in the female's best interest to reproduce frequently once she has secured a quality mate, so you'd expect sex to be on the mind of males more at the beginning of encounters while in females to be more during the long term.
…In category 1, “sex as personally and physically pleasurable,” statements included:
- I should get drunk to enhance my sexual experience.
- If I want to be close to someone, I should have sex.
- I should have sex with my partner so he/she will not leave me.
- I should have sex with as many people as possible.
In category 2, “sex as beneficial in creating positive feelings about oneself,” statements included:
- Sex makes my partner love me.
- I feel attractive after sex.
- I trust my partner more after sex.
In category 3, “sex as personally costly in terms of having negative emotional, psychological or physical consequences,” statements included:
- Sex makes me feel guilty for violating my morals.
- God will punish me for having sex.
- Having a one-night stand makes me feel cheap.
- I will get an STD by having sex.
In category 4, “sex as a violation of social injunctions," statements included:
- I should engage in premarital sex.
- I should be with my partner a long time before I have sex.
- I should not have sex because I’m too attached to someone I’m having sex with.
For the male it is important to figure out which females are receptive, and thus worth investing resources in courtship. Unfortunately, in humans we lack the fire-red bottom indicator of other apes, and thus it is difficult to detect intentions especially from afar (or in smoke-filled dark nightclubs). This may explain why, when looking at pictures of naked woman, man spend more time looking at the faces than females looking at pictures of naked man. Man need to empathize and recognize facial traits that indicate willingness while females need to look at the quality of the genes by inferring from the whole body. Willingness I assume, is much less of a factor.
This balance of quantity/quality is what makes sexual reproduction so great. Mixing the genes is just an added bonus. It is like the offer and demand paradigm, which makes capitalism so effective at maximizing profits. This explains why for example in a mite species which as reproduced asexually for millions of years, and quite successfully, sexual reproduction re-evolves independently. I'm inclined to think it is a universal imperative for any life form complex enough. On whatever planet we find life, we'll find evolution and we'll find sex, if the lifeforms are advanced enough. Perhaps there is even causation here.