One of the jobs I did when I first started in the audiobook industry was proofing: listening to the recording while reading along. It is an interesting job, which calls on a very specific and sometimes peculiar set of skills. It is very easy to become entranced by the story and lose focus on the task--to find errors. The eye and the brain don't always work together the way they should. This is true for both the narrator and the proofer, so you can see how this could get complicated.
The eye or the brain makes a decision about what it thinks a word is, without really seeing it. Sometimes crazy words that are not even in the script will pop up in the recording and you think (arrogantly and judgmentally), "What were they thinking?" Or you are listening and following along in the script and your eye and brain seem to agree with what the narrator is saying, but something seems wrong somewhere in your gut or the back of your neck, so you stop and rewind and go over it again and sure enough there was a mistake!
The thing I learned, which was eye opening and comforting at the same time, was that everybody makes mistakes--crazy mistakes. I was listening to people at the top of the industry--Simon Vance, Steven Rudniki, Barrett Whitener, Bernadette Dunne etc. And even they make some crazy mistakes. And now that I know more, I understand just how few mistakes they actually make, and how good they are!! When I started to record myself, I was horrified at the proofing notes that came back on my programs! I was so careful! How is it possible I made 5 errors on that one page?! I have learned to be humble, do the best I can, and just expect to make corrections; It is part of the process.
And I know not to try to work for too long a period without taking a break. I can assure you that the 5 mistakes on a single page happened after 3 hours of continuous reading. It is important to give the eye and brain a break even if the voice is holding strong.