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.
I've seen an article on LW about Santa Claus and most people were very keen on not lying to their kids (and I agree). I have a little kid who is generally quite truthful, innocent enough not to lie in most cases. I noticed recently that when someone asks him, "How are you", he usually answers in detail because, well, you asked, didn't you? When I was a teenager I hated people who lied and I tended to ignore these unwritten social rules to the extent I could. I.e. I didn't ask if I didn't want to know and people thought I was rude. So, my question is, should I teach him to lie upon these occasions?
More broadly, I was thinking, why am I committed to being truthful, in general? I guess because I would hate to be lied to myself. This is a kind of magical thinking maybe, or maybe it's a part of the social contract. This sort of lying in fact promotes the social well-being because to answer truthfully creates an unwelcome burden on my interlocutor who asked out of politeness and is not in truth interested. But it still feels wrong to lie. Even more wrong to teach your kid to do so.