This morning, I used the phrase
I didn't sleep very well, I don't think.
when speaking to my Colombian friend and he asked me what on earth I was talking about.
I thought about it and realised that this is idiomatic usage and that despite saying "I don't think" you are actually expressing what you do think.
Generally the form is
[expression of negative opinion using negative grammar] + "I don't think".
I didn't sleep very well, I don't think. => I think I slept poorly.
I won't get there very early, I don't think. => I think I will arrive late.
The first part is an opinion about what something is not, rather than what it is, i.e. my sleep was not good; my arrival will not be early. You wouldn't say:
I slept badly, I don't think.
It seems like "I don't think" is a way of intensifying the sentence, because it doesn't modify the meaning of the initial statement in any way. We seem to use it to express disappointment with a situation, but there might be more reasons.
- Is there a name for this usage?
- Do you use it to express anything other than disappointment?