When I was in high school, several of my classmates had jobs as tomato pickers. The interesting thing was that some of them got paid per tomato while others got paid by the hour. The ones that were paid per tomato definitely seemed to work a lot harder. So much so that they didn't want to waste time on bathroom breaks and just peed between the tomato plants instead.

This essentially taught me two things: 1) performance pay really works and 2) always wash your vegetables.