As an adult, I know myself and my relationship to tasks enough to say, "I need to have the TV on while I grade papers" (CSI and Law and Order work really well for that, for me). That kind of noise helps me block out the noise in my head long enough to get a grunt task done. I even have a mix on my iPod called "Music for Quiet Productivity". It has lots of music with some rhythmic texture, with no singing, or singing in a language I don't understand.
Or, "I need to have silence now, so I can concentrate on this problem." Or even, "I'm getting that creative, visual design urge, so I'm going to work on a dorm design in Sims2 before I go into the classroom this weekend."
A kid could figure this kind of thing out in middle school or high school with some guidance and a little bit of freedom to experiment.
