Nobody ever actually told me, as a kid, that I should try modeling people, try getting inside their heads, as a mode of navigating social situations and understanding the world in general. Empathy develops gradually on its own in children, and we are generally left to just figure out that it's good for something other than making us feel guilty.

I suggest you do not say to your child, "Lie more." Instead say, "Try to imagine you are other people. Ask what states of mind they might be in that could make them say what they say and do what they do."

This could lead to the child understanding when lies actually matter in an instinctive way.