"Pretend to not" vs. "Pretend not to" [duplicate]

Possible Duplicate:
Order of “not” with infinitive

The following are both accepted as grammatically correct, right?

You pretend to not notice.

You pretend not to notice.

However, if I think about it, it seems like the first one is correct but not the second. Why would that be?

It's almost as if the second one is saying "You don't pretend to notice," which means something different from the first.

Both forms are grammatically correct.

In this example, I slightly prefer the second — it flows a little better, to my ear; and pragmatically, people who believe that split infinitives are Wrong might hold the first form against you.

The second form doesn’t seem ambiguous to me in this example, since I pretend not isn’t an idiomatic way to negate I pretend in modern English. There are analogous examples where it certainly would be ambiguous, though; for instance:

My intention in writing this is not to offend grammarians.

Here, not could be negating either was or to offend, giving two quite different meanings: perhaps I have some quite unrelated intention, or perhaps I’m specifically trying to be inoffensive. So in this case, to give the latter meaning, I should rather use the first form:

My intention in writing this is to not offend grammarians.

Language Log has a couple of similar examples.