  Everyone has done this. Someone has just said something to you, and you heard and understood it, yet you have to stop, re-process what was just said to you, just to form a lucid response.
To frequently we have our shilds up - so strong that that we can't even pay attention to what is going on outside of it. I asked at least sixty people a very simple question last night, so obvious as to be cliche', just in a different way. Instead of asking people, 'Paper or Plastic? ', I asked if people had a bag prefferance. 46 of them required a restatment of the question to understand it.
28 needed the question explained. A good number of them apologized, and stated variouse things explaning thier lack of attention. This little experiment verified a nasty habit that a good portion of the population is acustomed to. We seem to all be on auto-piolet. we prepare to answer the questiones that we exspect will come, not the ones that are asked. This lack of living beyond ones-self was what I exspected, but to a degree I didn't see comming.
Oddly enogh, it was another customer that brought the next idea to mind. A young girl, who reportedly never stopped talking before, had shaved her head and apparently taken a vow of silence. The concept of bending your whole will to listening and contemplatling that wich surrounds you is very enticing. Then eventually only speaking when you've got something that isn't automatic and empty to say. It sounds obvious and yet, impossible at the same time. 
