Familiarity and heightened perception

Spartan: the loneliness of the business traveller, Stavanger, January 2008
Inspired by Doug Stockdale's Insomnia: Hotel Noir series

So I'm back in Norway (Stavanger) for the week - first time back in four years (thereabouts). It's all so familiar (even the work, which is follow-up to stuff I did just before I left).

This had me thinking about the nature of perception, the relationship we have with the familiar (in general) and the relationship I have with my surroundings as a photographer. Let me explain.
This is actually the first time in a while that I've returned to a location after a long time away, certainly the first time since I seriously got back into photography. One thing I have been noticing are the little details - e.g. walking out of the wrong door of the airport because they've restructured the interior. When so much is familiar, the small differences stand out. I am unsure, though, as to the source of my observations. Is this simply the fact that one does notice small differences amongst the familiar? Or is it something more fundamental to someone who looks at the world photographically - constantly noticing small things, thus more likely to observe the differences? On a personal note, have I really got that degree of sensitivity to the world around me that it would be the case?

No answers but plenty to ponder over a beer of an evening.