A snippet from an article at Future Hi about selective vision: "The number I've learned is that we can pay conscious attention to at the most 5-7 different items at the same time, and even that is a stretch. If we're exposed to more items, we'll start dropping some of them from our awareness. Naturally, if we've been asked to pay attention to a certain set of items, it is the other ones that we're likely to drop."
The whole article is worth reading, as is the one that he quotes from at The Telegraph.
Future Hi goes on to say "If a certain problem space involves more than a handful of simultaneous inter-connected factors, we're in trouble. Chances are that a majority of people will refer to some simplified political or religious ideology or belief system, containing less than a handful of key points, rather than dealing with the actual complexity in front of them."
Ah.. yes, I can think of tangents upon tangents that follow this line of thought.
A blog to note who apparently linked to the original story at The Telegraph is Puzzlepieces. I think this is one I will go back and wander through a while.