Promises, like contracts, are inherently incomplete and rarely specify what the promisor ought to do in different possible contingencies, thereby being apt to be interpreted differently by the promisor and promisee, with their conflicting interests, and in a self-serving manner whenever circumstances change. This article studies the effect of the incompleteness of a promise on the decision to keep the promise and on individual beliefs that are relevant for the social norm of keeping promises. It investigates, in a laboratory experiment, how individuals form beliefs about how promisors behave, how promisees expect promisors to behave, and how neutral individuals evaluate the immorality of breaking promises when a contingency that was not explicitly addressed by the promise materializes. Promisors distort their beliefs to breach without incurring guilt or moral costs when the promise is incomplete, but even neutral individuals believe that breach is more socially acceptable in this case. Results further reveal substantial heterogeneity in individual beliefs, providing insights into why people do not always respect a fundamental social norm such as keeping promises, at times violating it and at times keeping it.

中文翻译：

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不完全的承诺与守信的规范

与合同一样，承诺本质上是不完整的，并且很少具体说明承诺者在不同可能的意外情况下应该做什么，因此很容易被承诺者和受诺者以利益冲突的方式做出不同的解释，并且每当情况发生变化时就会以自私的方式进行解释。本文研究了承诺的不完整性对信守承诺的决定以及与信守承诺的社会规范相关的个人信念的影响。它在实验室实验中研究了个人如何形成对承诺者行为方式的信念，承诺者如何期望承诺者的行为，以及当承诺未明确解决的意外事件发生时，中立的个人如何评估违背承诺的不道德行为。当承诺不完整时，许诺者会歪曲他们的信念来违背，而不会招致内疚或道德成本，但即使是中立的个人也认为，在这种情况下，违背行为更容易被社会接受。结果进一步揭示了个人信念的显着异质性，提供了关于为什么人们并不总是尊重基本社会规范（例如信守诺言）、有时违反它、有时遵守它的见解。