Since when were human males and females separate species?  The economy of motion issue is more than trumped by the fact that the act of flushing causes a fine mist to spread as far as 6 feet from the bowl. Those who prefer to have no sewage mist on their toothbrushes (which are presumably within range) will find it most advantageous to put down not only the seat but the lid.

And be sure to wash your hands afterward, preferably turning on the water prior to touching the toilet.  it's not the trembling *hand* that they're complaining about ...  If the guy finds it down, he puts it up. If the woman finds it up, she puts it down. Putting it up or down is the same amount of work, so I see no rationale in a couple for forcing it to be put either up or down.

Furthermore, it's the same amount of work to move the seat before or after it's used, it's just a question of who's doing it, so if you are moving the toilet seat after you're done it's a partial waste of time because the next person to use it might want it the same way you had it.

If a woman insists you put the toilet seat down, this implies she thinks her time is more valuable than yours, so unless it really is, I would take this as a very bad sign.  During the day there may not be much of a difference - but will it really hurt to keep the seat down at night when a woman half asleep will end up with an awful surprise if she sits before looking? This is especially a problem when pregnant - urgency often lends to overlooking things like turning on lights and checking seat status!