Why do people keep their promises? An experimental test of two explanations

Numerous psychological and economic experiments have shown that the exchange of promises greatly enhances cooperative behavior in experimental games. This paper seeks to test two theories to explain this effect. The first posits that individuals have a preference for keeping their word. The second assumes that people dislike letting down others' payoff expectations. According to the latter account, promises affect behavior only indirectly, because they lead to changes in the payoff expectations attributed to others. I conduct an experiment designed to distinguish between and test these alternative explanations. The results demonstrate that the effects of promises cannot be accounted for by changes in payoff expectations. This suggests that people have a preference for promise keeping per se.

大量心理学与经济学实验均已证实，承诺交换可显著提升博弈实验中的合作行为。本文旨在检验两种用以解释该效应的理论。第一种理论假定个体具有信守承诺的偏好；第二种理论则认为，人们不愿辜负他人的收益预期。依据第二种理论，承诺仅通过间接路径影响行为，即承诺会改变他人被赋予的收益预期。为此，笔者设计并开展了一项实验，以区分并检验这两种竞争性解释。实验结果表明，承诺的效应无法通过收益预期的变化得到解释，这意味着人们确实具有信守承诺本身的偏好。