So the key phrase is "explicitly socially acceptable"?

I often see people napping in all of the above, both here in Russia, around Eastern Europe and in South America. And it's no big deal most of the times.

And things like sleeping on the bus/train or sitting on a bench seem to be normal all over the world.

The catch is, i never been to either Japan or USA, so i can't set the zero properly.

In my experience in most parts of the USA and Canada at least (and I'd guess in many places in Northern Europe), napping in public places is frowned on except in pretty specific cases - parks, beaches, etc where the purpose of being there is to relax.

Of course you do see it on public transit in the early and late hours at times, and it's not a big deal, but its definitely not 'normal'. Napping at work is especially frowned upon, with perhaps the exception of someone going out to the park during lunch time.

The general feeling/culture (not necessarily my personal opinion) is that you should have had enough sleep the night before so that you can be productive for the day's work. If you've stayed up so late (partying or whatever) the night before such that you need rest during the day, you're short-changing your employer and teammates. A nap might be the right thing to do to restore your energy, but you should not have put yourself in that position to start with.

Of course these days I don't need to stay up half the night to feel like I need a nap in the afternoon... :)

[edit] After reading the article, I see that the Japanese culture connects the tiredness with working hard/late, which changes the perception. I think in the US and Canadian culture this can happen in some extreme cases - we've all heard (or lived) stories of people working like crazy to meet project deadlines, and sleeping in the office, etc. And road-warriors fighting jet lag are often given some credit for that tired/haggard look. Blue collar workers are more prone to given respect for being particularly tired at the end of the day, but napping or dozing off is still not really rewarded/honored like it seems to be in Japan, because of the quite different work-time expectations.

I spent a year studying in university in Japan, taking engineering classes with regular students. The number of people sleeping in class was sometimes impressive - in the worst instance I remember it was about a third of the class (but thankfully, usually a lot less). The professor just ignored them and kept going.

The real shock for me was when I went back to Canada and realized I'd picked up the habit inadvertently! I would naturally fall asleep in some boring classes and had a lot of difficulty stopping that. Generally the prof would notice and call me out to everyone's amusement, or a neighbor would give me a nudge. It really did not feel acceptable to sleep in class as in Japan.

Sleeping in public is pretty weird in the US. Napping at work is definitely frowned upon, and napping in a coffee shop, public transportation, etc, is unusual but happens. It's not necessarily socially discouraged, just odd.

Honestly, it never really occurred to me that people sleep in public in other parts of the world.

And when it does happen in the US, you start to worry if the person is having difficulties, and whether you should help them by waking them up. Especially on trains.

I used to set my alarm on the Caltrain and sleep during my commute to the south bay every day. If someone like you had ever woken me up, I'd have been pissed. In months of commuting before I moved down to Mountain View, nobody ever did see fit to rob me of my precious last hour of morning sleep though...

Nah, it's all good, I probably would have just stolen from you :)

That's right. I live in the US and never saw any problem with napping in the college library, but one time I fell asleep out in my car while waiting for my child's class to end, and someone woke me to see if I was ok. Well I was just fine until you woke me, thanks!