A recent study on how to encourage honesty in children found that showing negative consequences for lying did not work, but showing positive consequences for being truthful did. Just throwing that out there. Otherwise, no advice. I have one of these, and the other likes to copy her just to drive me closer to the brink. I assume.

I may be tired. Ahem. I recently instituted a "Do one request without arguing per day" rule, if that gives you an idea.