The article explores how different types of rewards influence the behavior of buyers and sellers in long-term contracts. They tested their ideas using experiments and found that both formal rewards (like bonuses) and informal rewards (like promises) can work together to improve outcomes. While some thought formal rewards might replace informal ones, the experiments showed they can actually enhance each other. However, the study also found that people don't always punish bad behavior as expected, which could affect how these rewards work in real life.