Question tags — "did you" vs. "didn't you"
Typically, when we ask for confirmation/denial of a statement, we say something like the following:
We turn left here, don't we?
You have a cat, don't you?
We've met before, haven't we?
pairing a positive statement with a negative question, or
We don't need that, do we?
You don't know anything about this, do you?
pairing a negative statement with a positive question.
However, sometimes positive statements are paired with a positive question
We take a left, do we?
You had to be a big shot, did you?
You've been to Prague, have you?
Is this correct? Does it change the meaning in any way? Are the three forms interchangeable?
Solution 1:
No, they aren't interchangeable.
A tag question is a device used to turn a statement into a question. It nearly always consists of a pronoun, a helping verb, and sometimes the word not. Although it begins as a statement, the tag question prevails when it comes to the end-mark: use a question mark. Notice that when the statement is positive, the tag question is expressed in the negative; when the statement is negative, the tag question is positive. (There are a few exceptions to this, frequently expressing an element of surprise or sarcasm: [examples omitted])
Source: Capital Community College Foundation, Guide to Grammar & Writing (2004).
Solution 2:
Tag questions always swap negative values; like multiplying by minus one.
Although tags with two negatives are impossible:
- *You never went there, didn't you?
- *She isn't coming tonight, isn't she?
Tags with two positives do occur, as noted.
However, they are a different construction; they're not questions, but challenges:
- She's coming tonight, is she?
- We turn left here, do we?
Each of these will be delivered with quite different intonation than what a genuine question would have. In addition, each of these can be preceded by a very dramatic So, ...
- So, she's coming tonight, is she?
- So, we turn left here, do we?
In effect, instead of actually asking for information, the speaker in this construction is challenging the addressee to a confrontation of some sort; one might be said by a wife to a husband about an ex-wife, for instance, and the other by a passenger to a driver while lost.