Guess What: TV is Bad
This makes lots of sense. I only wonder the age range for which it remains true that background TV might distract from the brain's development. Why think it effects only the little kids?

[I]n the new study, researchers say the disruptive effects were "real but small," amounting to a few seconds in many cases. For instance, kids played about 90 seconds less in the half hour with the TV on — they looked momentarily at the screen, then went back to their toys.

But researcher Daniel Anderson, a psychologist at the University of Massachusetts-Amherst, says he's concerned the effects could be cumulative.

"It's that situation that I'm most concerned about, when you look at TV as being a disruptive influence hour after hour, day after day, week after week, year after year," he says.

Perhaps most significant: When the TV was on, kids of all ages played with a given toy — a jack-in-the-box, a baby doll, blocks, a toy telephone, a school bus with toy passengers — for about 30 seconds, on average. Without TV, it was 60 seconds.

Researchers say solitary play, especially with toys, offers many benefits. It allows children to practice planning ahead and develop cognitive skills.

Obviously it's even more important with very young children to remove that distraction, but since we know that the brain continues to develop for several years, it makes you wonder if background distractions can hamper you later in life as well. I also wonder if music can have the same disruptive impact.