The habit of asking "how are you" when one is not really interested in the answer is not a human universal; it's a distinctly Western phenomenon.
You can see this pointed out, for example, in Brat 2 (although the scene in question also goes on to engage in some rather less-accurate anti-American stereotyping).
It accords with my own experiences in Russia, which are that you should not ask this unless you are ready to accept an earful.
distinctly Western phenomenon
The exact phrase is specific to few languages, not universal in the West. The literal translation would work e.g. in Spanish or Serbian, not in French (there the equivalent "(comment) ça va" means "(how) does it go", I am not sure how a Frenchman would interpret "comment es-tu") or Polish ("jak sie masz" = "how do you have yourself", direct "jak jesteś" would be ungrammatical). Each language usually has an arbitrary set of standard questions used for greeting, every...
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.