Oftentimes there are multiple people replying to the same question. The duplicate answers leads me to believe that no one is aware that others are answering the question at the same time. Is there a way to tell if someone else is in the process of answering a question?
If there were, I could just write a script that would automatically load the page and put text in the box immediately on a question appearing, to discourage others from answering until I could get a real answer together.
You will get notified (eventually) by a banner across the top of the page if new answers are actually added, but I always just make sure I've copied my answer to the clipboard, then reload the page before submitting, to reduce the change of duplicating or posting a worse answer.
No, there is no way to tell until someone posts the answer, at which point (or soon after) you will get a bar at the top of your screen telling you that there are new answers, and asking if you want to load them.
However duplicate answers are not necessarily a bad thing. If someone comes along and posts the same answer hours or days later without expanding on it anymore than anyone else, that's just useless, but, in the first few minutes having duplicate answers helps to reinforce the answer.
If I'm leaving an answer and when I hit submit someone has beat me to it and write approximately the same thing, I just upvote their answer. I obviously believe it to be correct, so it deserves my vote for sure. If the same answer is posted by someone within a couple minutes too, I'll assume they were typing it already and haven't seen that it's already been answered. So if I see it I'll upvote it as well. The time an answer is posted doesn't affect the quality of the answer.
The point in me saying all that is that it doesn't hurt if someone is answering a question at the same time as you, and they beat you to it. You may still even get some upvotes from them, and others if it is a correct answer. If you want to compete with the first answer for votes and acceptance though you usually need to expand on it more.