This seems to be at the root of a great deal of interpersonal dissatisfaction. And I do want to stress “implied.”
Not: “let’s be significant others.” later: “thanks for the sex. I’m breaking up with you now.” The relationship basis was state, not implied; and arguably breached irresponsibly.
What is a reasonable expectation, if any, that divides friend/aquaintance and 1-nighter/FOB/SO?
In most cases, the responsibility for a pregnancy, no matter who says he/she is using birth control or is sterile.
I think you have a responsibility to pay attention and not be willfully ignorant. If you know someone is emotionally invested in you, you can’t fuck them, walk away and be like “Whoa, I never said it meant anything. Unbunch your panties”. And you can’t just avoid thinking about the issue because you don’t want to realize anything that will interfere with your fun. You can’t tell yourself someone isn’t emotionally involved because you wish that they weren’t.
That said, if you are a personally who genuinely casually sleeps around and you have every reason to believe the person you slept with also casually sleeps around then nothing is automatically assumed in terms of a relationship.
I do think you have an implied responsibility towards any children that are created.
I do think you have an implied responsibility to treat the encounter respectfully and not insult dignity of the person you are with by mocking them later or revealing information they wouldn’t want made public.
You have an implied responsibility to reveal any sexually transmitted diseases before sex and to contact your partner about any sexually transmitted diseases you subsequently discover that you exposed them to.
On an emotional level, which seems to be what the OP is asking about, you have an implied responsibility to be aware of what level of commitment your partner feels is indicated by the sex and to clear up any misunderstandings before the sex.
Breakfast. I always do up a nice breakfast.
Kids if there’s any possibility of 'em, diseases and the prevention thereof, and responsibility to learn in advance whether the other person just wants casual sex or is emotionally involved.
Oh. And responsibility to call 9-1-1 or drive them to the emergency room if you’re doing something real kinky that goes wrong, not flee like a douche. I think most folks would agree never to have sex with you again if you jumped out the window, hopped on your bicycle and left someone tied up on fire or something.
Not to spread disease
Use birth control if necessary
Don’t lie to people
Do it with your eyes open, taking responsibility for your own actions as an adult, and don’t assume the victim-tard stance after the fact ie “I was drunk, lonely, vulnerable, and you used me”