On the Interaction of Chance and Promise

Résumé : It is commonly accepted that promises with open-ended text increase trust and trustworthiness. One of the theories explaining this behavioral pattern relies on shame. To mitigate shame, it is a common feature in experiments exploring promise to add a chance event to the trust game such that the trustor is unable to discern whether a bad outcome is caused by the trustee’s action or bad luck. In a series of experiments, we vary the chance event’s presence and location—placing it before or after the trustee’s choice. We also vary the possibility of making a promise. We find that while the presence of the chance event moves trust and trustworthiness in the direction predicted by shame theory, moving the location of the chance event in a strategically isomorphic fashion can drastically alter the outcome. That means the shame can be ruled out as an explanation, at least not without other factors. We further show that while an affirmative promise makes a positive difference over a non-affirmative promise, the negative impact on trust by the non-affirmative promise far outweighs the positive impact on trust by an affirmative promise, meaning that the mere possibility of making a promise has an overall negative impact on welfare.