When you first arrive in Japan, you're hyper-aware of everything and note all sorts of curious differences. For instance, many people carry around paper shopping bags in addition to their regular complement of handbags, backpacks and briefcases. It looks like they've all been on shopping sprees but the truth is that they just carefully store and re-use the bags to carry random things. One of my students told me she did this for things which were on a one-way ride so she could toss the bag away when it reached its destination.
These little things often make up more of the framework of cultural differences than the big things. Most small differences are not arbitrary and are motivated by some less trivial factor if you scratch a bit and look under the surface. Personally, I think the omnipresent shopping bags are social camouflage for carrying boring, ugly, or possibly embarrassing things. They look like they've just been out shopping at a nice, semi-posh department store, but they're really carrying a bag full of old books to take to "Book Off" (a book exchange shop where you can get new books for 100 yen, about a dollar, and return old ones) or a wad of clothes to see them through a night at a love hotel with a paramour.
I've become so accustomed to a lot of these small things that they have little or no impact on me these days, which is rather a shame. Occasionally though, I'll be inconvenienced enough to notice or one of my students will tell me something that they notice. Recently, one of my students related a story of an experience she had at Costco which brought one of these small differences to mind and how transplanting an American way of doing something into Japan can have unexpected consequences.
This particular student mentioned that, in America, doors in public lavatories don't go all the way down to the floor while Japanese doors in public toilets nearly touch the ground. I had forgotten about this, but I think the U.S. ones have a large gap at the bottom. Costco branches in Japan appear to have adopted the American style, perhaps because they felt it was in keeping with all of the other Costco conventions (like selling food in quantities large enough for healthy Mormon broods to live off of until the apocalypse).
My student was using the facilities when she heard a mother and her little boy talking. Obviously, the boy was too young to stand outside alone or to use the men's room on his own. Suddenly, the little boy's head popped out from under her stall's door and he was looking at my student as she sat on the toilet. In a state of shock, embarrassment and anger, she rapped on the door and the little boy withdrew. She told me later that she was furious at the invasion of privacy and wanted to let the mother have it for not controlling her son or keeping a better eye on him in the lady's room, but the mother and son had disappeared by the time she left the stall. She told me she had been carrying around the tension from this unreleased frustration for a day.
I concluded, and she concurred, that the boy's mother was probably using an adjacent stall and he though he was catching his mother's attention rather than getting a head start on a career as a pervert. When asked if this ever happened to me, I told her that it had not. This might be because I was lucky, but I think that circumstances which are common in a culture, such as toilet doors with gaps, tend to develop behavioral conventions to deal with them in a manner which is appropriate or those circumstances are removed promptly. That is to say, if a situation where privacy can be invaded is everywhere, the vast majority will not take advantage or that avenue of invasion will be shut down.
Since doors with big gaps are not a part of Japanese culture, the situation unfolded rather unfortunately for my student. I think a mother in the U.S. would have taken the child into the stall with her or he would have knocked on the door or spoken through it rather than stick his head under the gap to check for his mother. This was a reminder, once again, of how incidental environmental factors shape behavior in unexpected ways and how transplanting a situation wholesale from one culture to another may have unpredictable results.