The way that you stop your kid from lying is the same way that you change anything.
You have to make the wanted behavior the product of inner responsibility.
For the same reason, you are not going to permanently lose fifty pounds, become a runner, or keep a journal based on someone shaming you.
Any parent knows this, but the second you make a desired behavior the force of an authoritarian, “Because I said so, or else.” the battle is lost.
You see, instilling personal responsibility changes behavior.
Rules create rebellion.
Adults facing the child-rearing experience can take a cue from the Freedman study. Suppose a couple wants to impress upon their daughter that lying is wrong. A strong, clear threat (“ It’s bad to lie, honey; so if I catch you at it, I’ll cut your tongue out”) might well be effective when the parents are present or when the girl thinks she can be discovered. But it will not achieve the larger goal of convincing her that she does not want to lie because she thinks it’s wrong. To do that, a much subtler approach is required. A reason must be given that is just strong enough to get her to be truthful most of the time but is not so strong that she sees it as the obvious reason for her truthfulness. It’s a tricky business, because exactly what this barely sufficient reason will be changes from child to child. For one little girl, a simple appeal may be enough (“ It’s bad to lie, honey; so I hope you won’t do it”); for another child, it may be necessary to add a somewhat stronger reason (“… because if you do, I’ll be disappointed in you”); for a third child, a mild form of warning may be required as well (“… and I’ll probably have to do something I don’t want to do”). Wise parents will know which kind of reason will work on their own children. The important thing is to use a reason that will initially produce the desired behavior and will, at the same time, allow a child to take personal responsibility for that behavior. Thus, the less detectable outside pressure such a reason contains, the better. Selecting just the right reason is not an easy task for parents. But the effort should pay off. It is likely to mean the difference between short-lived compliance and long-term commitment.
-Robert Cialdini, Influence