It's Amazing, Isn't It?

I never cease to be amazed that small children are like sponges. They soak up any and all information, bad or good. The other night, we had gotten home particularly late. I popped the girls into bed and they were sound asleep. David stayed up a bit later, though, because he had taken a three hour nap just a little before. On top of being off schedule, he was not feeling well and sporting a runny nose. So, he and I were snuggling on the couch watching PBS. It was a Sunday night, so there was a program on involving a chamber orchestra and the most beautiful music. I should back up to say that we have studied (briefly) the orchestra and it's parts. Anyway, I comment to David:

"Isn't this music just beautiful, David?"
"Yes, mama-that's the strings."
Me, looking a little shocked that he remembered that violins are indeed part of the strings "Yes, that's right! Those are violins."

If he can remember that, just how come he can't remember not to grab the toilet paper and run through the house trailing it behind him?