I would like to add that for some people, this kind of thing seems VERY much to be an executive issue-- which means that those people simply need to learn to write MORE of their work out, and check it more meticulously, than those whose executive function develops earlier.
I was not one of those people, incidentally, but DH and DD both are.
DH made far, far fewer of these mistakes when a graduate student (he was older), and DD makes a ton of them and always has. It's greatly exacerbated by her acceleration, which places those executive demands under significantly higher load than "age appropriate" if that makes sense.
This is one of those quirky results, IMO.
