I think part of the reasoning behind this type of response is that each response is dealing with a different level of abstraction. > A: Did you see any birds at the park? > B: Yeah, no - I didn't see any. B is first acknowledging the question and it's intent - as well implying that maybe he did look for birds - which then flows into the fact that 'no' - he did not see any. This can be done with the 'No, totally' exam…
Someone : "I thought you really wanted to use the paintbrush. Did you see the if there were any rollers?"
Me (mental response): "No (I didn't want to use the paintbrush). Yes (I did see the rollers) but they looked bad".
Me (actually said out loud): "No. Yes, but they looked bad"