I'm not tired, am I?

[keannu]

I think A is correct, but what about B? Is it also correct?

gz209
A : I'm tired, aren't I?
B : I'm not tired, am I?

[probus]

A is ungrammatical but idiomatic. A person might use it as an excuse for a mistake just made.

B is grammatically perfect and could be used by someone musing over why he or she just made a mistake. The assertion is that fatigue was not the cause, but an element of doubt is implied.

[5jj]

A is ungrammatical but idiomatic.

'Aren't I' may not appear logical, but it is grammatical.