"For months, an old man endured the insults of a group of boys as they ran across his yard. One afternoon, after listening to another round of jeers, the man came up with a plan. He met the children on his lawn and announced that anyone who came back the next day and yelled rude comments about him would receive a dollar. Amazed and excited, they showed up even earlier on Tuesday, hollering insults with enthusiasm. The old man came out and paid everyone saying, "Do the same tomorrow and I'll pay you twenty-five cents." The kids thought that was still pretty good and came out on Wednesday to taunt him. At the first catcall, the man again paid his hecklers. "From now on," he announced, "I can give you only a penny for doing this.’" The kids looked at each other in disbelief. "A penny?" they repeated scornfully. "Forget it!" And they never came back again."
(from Alfie Kohn, Punished by Rewards - The Trouble with Gold Stars, Incentive Plans, A's, Praise, and Other Bribes, 1993, Houghton Mifflin, pg. 71-72)