Template:Ariely daycare quote
Before the fine was introduced, the teachers and parents had a social contract, with social norms about being late. Thus, if parents were late — as they occasionally were — they felt guilty about it — and their guilt compelled them to be more prompt in picking up their kids in the future. But once the fine was imposed, the daycare centre had inadvertently replaced the social norms with market norms. Now that the parents were paying for their tardiness, they interpreted the situation in terms of market norms. In other words, since they were being fined, they could decide for themselves whether to be late or not, and they frequently chose to be late.