I would shake my head for 'no'.
Rover
My daughter has done the same, but then my daughter enjoys being deliberately perverse at times. I think you'd agree, Bob, that most native speakers would have said 'no' in that situation?(Even between two English speakers, though, there is room for confusion. Last Christmas I asked my daughter 'Don't you want some tea?'. assuming she did. She answered 'Yes', and then looked at me like a madman when I brought her some.)
Same in Polish... Whereas the preference is for "no" in such situations, "yes" is possible too. We often say, "Yes, you do or yes, you don't?" after getting our resopnse. I think I've heard it in English too.(Even between two English speakers, though, there is room for confusion. Last Christmas I asked my daughter 'Don't you want some tea?'. assuming she did. She answered 'Yes', and then looked at me like a madman when I brought her some.)