Oh, for God's sake. Locator, please. Original thoughts, have any? Highlandspring already asks these questions as a part of her job (which means she has access to the same articles you do; probably more). She just hasn't made that fact clear to people reading her 'questions' (although I wish she would).
Highlandspring, the action a parent must take will differ depending upon the age of the child and the child's understanding of what it means to tell a lie.
If the child is old enough to know right from wrong, then I suggest limiting discussion of the matter.
Plain and simple, let the child know you are aware s/he lied and that lying is unacceptable, period. No analyzing why s/he did it. No endless talking it over. Just identify it, mark it unacceptable and give one warning.
If it happens again, enforce whatever punishment is merited and go from there. Usually, consistency and follow through will work to deter the undesirable behavior relatively quickly; especially if you don't allow it to become habit.
Good luck to you and your readers.
Excellent and to the point.