Much of it is chemistry. There has been a lot of research on this particularly the past 5 - 10 years. I'm not sure where AS comes into the straight human chemistry, but there is a lot of science behind it. When I first began seeing Mr. Rath (my aspie husband), I was so attracted to him I felt sometimes like I would pass out, or throw up. (but in a good way). I daydreamed about him, and I loved the smell of him. I asked him once about our chemistry (in email) and in his typical fashion, he understood me to be speaking about cold medicine and gave me a rundown on the chemical properties. I said hmmm... no, I am talking about metaphysics.
Anyway, the other day after a thread here on "love" I asked him if remembers that he felt that powerful chemistry. He said no, he did not. Although he found me very attractive it took him longer to feel a pull, or draw, to think about me when I was not there and it wasn't for a long time that he felt really in love-in love.
So? Not sure how much of this is also nonverbal or being highly intuitive.