Choice quotes from the link:
"Yeah... it's that whole "own
little world" thing. Every day is sort of this struggle to keep in
your own little world... when you're on the subway, even in a large
crowd, it's this odd personal commute time. I've seen people
totally flip out when their "personal time" was interrupted on the
subway. People in NYC hate being brought out of their personal
bubble, so by and large as far as most of us are concerned we're
walking the streets alone, not surrounded by other creatures. You
just kinda put yourself into that zone after a while..."
"
In general, Manhattanites are in their own little world. Most walk
around with little regard for the person walking or standing
alongside us. Most seem to act as if they are the only person
alive, or like they are in their own homes. Money is king here, and
that is what most people respond to - not out of the goodness of
their hearts or because that was they way they were raised (despite
the quote in the article). In fact, whenever I act in a gentlemanly
manner (which I try to do as much as possible) I am met with
extreme surprise (and usually appreciation)."
I think both the comments apply Singapore as well. And most other
overcrowded cities in the world. 
