Let's play guess the picture!
a poorly drawn polar bear, clenching his teeth in a snowstorm?
a poorly drawn set of translucent beads on a string?
a poorly drawn version of the function y = |sin x|, reflected about the x axis?
No, it's not any of the above (well, except poorly drawn). It's the poorly drawn aerial view of an uncleared walking path on a snowy day. The thick black line represents the main walking path, made relatively easy to traverse by repeated walkings--but still not big enough for two people to walk side by side. The curves off to the side represent what happens whenever two people walking in opposite directions meet each other.
It's fascinating to watch. Generally, each person goes off the path to their right, and walks forward through untrod snow until they pass each other, then gradually return to the main path. What I find so interesting is that it's not one person standing to the side, so someone else can get by, like you'd do in a hallway--nobody gets to walk on the "good" portion. It's the equivalent of two people reaching for the last chocolate at the same time, and instead of one taking it, or sharing it, or starting a brawling smackdown over it, both decide to tactfully leave the box forever unfinished.
There's a certain level of basic politeness to it, but I think there's also a level of un-intimacy, and expediency. If you know the person in question, then such a situation is resolved by compromise based on your relationship with them. If you come across a colleague, you come face-to-face, and chat. If it's a superior, you move to the side and make way. But for a stranger, there's no real point in seeing who moves first, unless you're throwing around some deep-seated alpha male issues. Further, it's significant that both people are in transit; it's not like the chocolate scenario, because there's no immediate reward for "winning" the engagement. The fastest resolution is for both people to move off the trail and continue on their way.
Every now and then, someone, like my perennial favorite, Jean Jacques Rousseau, puts forward the idea that society is formed based on some tacit social contract. I don't agree with most articulations of this contract, because, like in Rousseau's case, they tend to take a specific society (18th century continental Europe) and universalize their theory based on that. That doesn't work. Even for my snow example: when I lived in the rural community of Wherever, many sidewalks wouldn't be clear until spring (usally in May). Thus, I deliberately walked slightly outside the "set" path, in order to enlarge it over a course of multiple weeks. Where I am now, in Blank, that action wouldn't make sense, since the city or the university cleans most of the side-walks on my path on a daily basis. So even within this very specialized case of snow walking, there's some diversity in behaviour. But once we recognize that diversity, we can still appreciate the shared commonalities.
Why have I thought so much about snow paths? Put it this way: I'm in my mid-twenties, I've never owned a car or taken a bus regularly, and I've lived through Canadian winters every year of my life. I HAVE SOME EXPERIENCE IN THIS AREA.