This feeling of "oughtness"

What is it? Why is it that in social situations, we feel we have an obligation to act a certain way?

I looked up the definition of deontic logic and it explained that the term deontic is derived from the ancient Greek déon, meaning, that which is binding or proper. But what is proper anyway? I guess this relates to my previous post about the meaning of the word professional. Both of these words are circumstantial.

However, to give an example, something we were talking about in class last week was how in America when someone sneezes, we have a need or feeling to say "bless you" afterwards. Sort of this feeling of social "oughtness." I can definitely relate (obviously) and I do feel that need to say "bless you" after someone sneezes, even if I don't know them. Sometimes I say it offhand at random places, like in a store or something when I hear a sneeze. Also, something funny, I usually find myself feeling a little insecure if I sneeze and nobody says the typical response to me.

Now I'm not really a religious person, but I still feel this need to say bless you and to be blessed after I sneeze. I just feel that it's what's proper.

Another example, it's just a social norm that if someone smiles or waves to you, you wave back. Something I found to be completely ridiculous yet kind of interesting at the same time was something that happened to me last week. I was walking on the sidewalk by the road and a car drove by me with people I didn't know and one of the guys in the back seat was staring out the window with a goofy look on his face and a hand up waving to me. I knew he was just joking around because he was definitely making a face, just trying to get a reaction out of me. Anyway, the strange thing was, even though I knew he was kidding around, I felt my hand want to go up and wave back to him. Just because his hand was up waving to me. Like this thought process happened first, and THEN I realized I did not know the person and he was kind of creeping me out. Funny huh?

-kp