心理学家德西做过一个实验：让一些孩子解答一些妙趣横生的智力难题。开始他对所有的孩子都不奖励，尔后，他把孩子分成两组，一组每解答一道难题就奖励一美元，另一组则没有任何奖励。在安排孩子休息和自由活动的时间里，他发现，尽管有奖励那一组的孩子在有奖励解答的时候解 Psychologist Dixie did an experiment: Let some children answer some of the most entertaining intellectual puzzles. At the beginning he did not reward all children, then he divided the children into two groups, one for each reward a puzzle for a dollar, the other group did not receive any reward. In arranging for rest and free time for children, he found that while the children in the group who rewarded had solutions when there was a rewarding solution