A few years ago I was visiting some friends in Germany and we were going for a walk along a nearby nature trail after lunch. There were five of us trooping along; my wife, our host, his two adult daughters and myself. On the whole, I don't think we looked too disreputable. You need to understand that walking after lunch – or dinner – is a very common activity in Germany, and there were various other people on the trail as well. I noticed a middle-aged couple walking towards us on the trail, with their pet Dachel (Dachshund) tagging along at their heels. I was looking forward to meeting the dog and getting a quick pet fix. I've been partial to these sleek little dogs since owning one as a youngster. However, as we came closer I realized that this was not going to happen. The couple kept their gaze stolidly a head and completely ignored us as we passed each other. To be fair, the members of our party kept up their own conversation with no indication that they noticed the other people on the path. Only the Dog seemed to give us a quick sideways glance before hurrying after his humans.
Glancing at my wife, I wondered if she had found anything curious about the lack of polite exchange, and she returned my look with a shrug. As I waited for a break in the conversation to ask why no-one had responded to the other people, a younger couple came towards us on the path. They were in an animated conversation of their own, but they also offered no acknowledgement as we passed one another. Curiouser and curiouser. Just as I was going to break in on the discussion of what was and was not appropriate to decorate a Christmas tree with, yet another person came walking towards us. This was a middle-aged man, who immediately hailed Detlev – our host – and proceeded to introduce himself to us and exchange pleasantries with Suzanna and Lisa. "Ah!" I thought. "I see! It is only people they already know that they greet."
Finally, when we arrived back at the house, and Detlev had told his wife about them running into Herr what-ever-his-name-was, I asked them why they didn't greet the other people we passed. Detlev's only response was an almost offended "But that would have been rude!" I didn't pursue it, but it did teach me a valuable lesson. It really hadn't occurred to me that something as simple and seemingly obvious as nodding "hello" to a stranger could be perceived in such different ways by different cultures – especially ones that seem, at least superficially – to have so much in common.
This of course can be taken much further. There are so many things that are embedded deeply in our minds, so that we don't question them. For instance, we take for granted that "grass is green" and "sky is blue". It doesn't occur to us to questions something that is so "obvious"; something we learned so long ago that we no longer remember learning it, and yet there is grass that is not green and there are skies that are not blue.
We humans have a great capacity to screen out what would otherwise overwhelm us. Our limbic system takes in the huge amount of data from our senses and then passes onto our conscious awareness a small part of that data which we experience as information about our surroundings. If we had to deal consciously with the fullness of all our sensory input, we would probably not be able to function very well. It seems that we have a means of doing something similar with other data as well.
I think that's about far enough on this train of thought for now. There's a big snow storm blowing in tonight, and I may have lots of time for deep thoughts tomorrow.