We just watched the Freakonomics movie, which describes among other things how co-author Steven Levitt tried to motivate his three-year-old daughter to learn how to be potty trained. As an economist, he surmised an incentive scheme: he would give her candy every time she used the toilet successfully. Before long, though, the daughter began gaming the system, increasing her frequency of bathroom trips by peeing just a little each time in order to pad her candy haul.
Contrast this with the recent excerpt in the Wall Street Journal from Amy Chau's book in an article titled "Why Chinese Mothers Are Superior" (you really have to read the whole thing to get the full effect):
I rolled up my sleeves and went back to Lulu. I used every weapon and tactic I could think of. We worked right through dinner into the night, and I wouldn't let Lulu get up, not for water, not even to go to the bathroom. The house became a war zone, and I lost my voice yelling, but still there seemed to be only negative progress, and even I began to have doubts.
It shouldn't be surprising to anyone that you get better results (at least from the parents' perspective) by brandishing a hefty stick than you do by offering a carrot of trivial value.