I’ve written a lot about the dangers of using rewards with students and the dangers of using merit pay with teachers.

And I’ve written about economists and schools — Part Two Of “Can’t Economists Stay Away From Schools?” — My Worst Fears Realized.

So what happens if you combine an economist, incentives and toilet training?

Here’s how NPR describes it:

On today’s Planet Money, we talk to economist Joshua Gans and his 11-year-old daughter.

Gans, who wrote a book called Parentonomics, tried to create a toilet-training economy for his young children. He rewarded them with candy for sitting on the toilet — and the older ones got candy if they helped the younger ones.

But, like tiny Wall-Street bankers, the kids figured out how to work the system for maximum advantage.

His daughter managed to go to the bathroom every 20 minutes, all day long. For a while, she got a treat every time.

She also wrung everything she could out of her brother:

“I realized that if I helped my brother go to the toilet, I would get rewarded, too. And I realized that the more that goes in, the more comes out. So I was just feeding my brother buckets and buckets of water.”

Thanks to Barking Up The Wrong Tree for the tip.