The first-person narrator

You need to be very skilled to speak and think in the voice of someone unlike yourself. So, when a novelist writes for her characters in the first person, the danger of slipping up is great. Of course, it can happen that, even when writing in the third person, the writer ascribes thoughts to her protagonists that they are unlikely to have, given the kind of protagonists they've been set up as being. That's an occupational hazard for any novelist. But in first-person narrative the danger is more acute. The writer's own diction can suddenly pop up in the mouth of the character - who will say 'inflection' or use a well-turned literary allusion when he's not been built as the sort of guy who would do that. It gets in the way.