In Look Me in the Eye: My Life with Asperger's, John Elder Robison writes extensively about his struggles making eye contact. From about the time he was in the first grade, he was constantly criticized and nagged for not looking people in the eye, with rather devastating effects on his self-esteem. The fact that he gave that title to his autobiography is testament to how deeply it bothered him.
I've never had Robison's genuine inability to look people in the eye. I can make myself do it, but it doesn't come naturally. Like Robison, "I don't really understand why it's considered normal to stare at someone's eyeballs." To me, the normal thing to watch when someone is speaking is the speaker's mouth. It's the mouth, after all, that's making the sounds. It seems to me that one is much less likely to miss any words if one sees them spoken as well as hears them.
The other normal way for me to listen is to stare off into space. Once in awhile, if something really interesting comes into view, I can get distracted that way, but usually if I'm not looking at you when you're talking to me, it means I'm listening really hard. I guess it looks like I'm not listening, though, because sometimes when I do it, people say, "Are you listening to me?" Since I have a good memory, I can usually repeat what they just said back to them more or less verbatim, which seems to convince them that I am listening. But it seems to bother people, so usually I avoid doing it.
I know that I'm "supposed" to be looking people in the eye when I talk with them, so I try. I don't really know how, though. I tried really hard when I was younger, but I think I overdid it. In my early 20s, a couple of people told me my gaze was "piercing" or "penetrating." Other people told me that I looked "right through" people or that they felt I was looking "right inside" them. Since I didn't want to make anyone uncomfortable, I stopped staring at people's eyeballs so much.
I still haven't really figured the whole thing out. I read in a magazine once that a good trick for shy people is to look at a person's forehead just above the nose -- supposedly, the person you're looking at can't tell you aren't really looking at their eyes -- so I tried that for awhile. It didn't really work for me. I found it distracting -- I kept noticing how many little hairs and wrinkles people have there, and things like that -- and my problem isn't that I can't look people in the eye, it's that I don't know how to look them in the eye. I don't know how long, or at what points in a conversation, things like that.
So now I just muddle along as best I can. I make eye contact during conversations, but it doesn't come natural to me. I'm like someone who's just learned a new dance step, but instead of "1-2-3-kick, 1-2-3-slide," it's "1-2-3-look at eyeballs, 1-2-3-not too long, 1-2-3-don't look into space..." It's a lot to remember. I can't just go with the flow, I have to think about it all the time. But I think I manage to come across as fairly normal. I hope so, anyway.