Tag question intonation

We vary the intonation of a question tag depending on whether we are asking a real question, or just using the question tag to keep the conversation flowing. See below:
Real question - rising intonation

You will do it quickly, won't you?

  John and Mark aren't English, are they?
Checking information or making conversation - falling intonation

We've seen that film, haven't we?

  Paul doesn't like mushrooms, does he?