Each year, I conduct an unscientific test of "teenagerism" by leaving an item in a spot that would require the boys to move it out of the way, step over it... OR, put the item away in its proper place.
A couple of years ago I left a basket of the boys' clean clothes at the bottom of the stairs. The clothes were easily identified as theirs and neatly folded. The two boys stepped over the basket or moved it to the side for 48 hours straight.
The test this week with Jan and Simon consisted of a package of toilet paper. I left it at the bottom of the stairs for the first 8 hours. Nothing. For the next 40 hours I put the TP on their toilet; they took it off... maybe 20 times. I left it on their sink... they took it off. This morning I opened the vanity door and put the TP away.
This unscientific test proves ... well, absolutely nothing. But I had a good time watching them be them.