We study whether and why the mode of decision making affects reciprocation in a binary trust game, using three preregistered online experiments. Trustees—some of whom were exogenously induced to be surprised by trust—either decided whether to reciprocate after observing their partner’s choice (hot mode) or committed in advance to a contingent response plan (cold mode). In our Baseline experiment, once participants gained experience, reciprocation became more likely under hot than under cold decision making, especially when trust was unlikely—consistent with a model in which positive surprise at being trusted increases the utility of reciprocating. Results from the other two experiments show that surprise promotes reciprocation only when trust reflects an intentional choice by the trustor and when cognitive load in the decision environment is not too high.

A lab experiment was conducted to investigate whether people are more inclined to reciprocate trust when their partner faces a larger opportunity cost of trusting. Participants played a series of binary trust games with varying sizes of opportunity cost. Trustees were more likely to reciprocate when the opportunity cost was higher. Additionally, trustors’ beliefs about the reciprocation rate also increased with the opportunity cost. Two psychological mechanisms could explain this effect: Intention—a higher opportunity cost makes the trusting action seem kinder, and Guilt Aversion—trustors may expect to receive more when forgoing a larger opportunity, leading trustees to reciprocate more to avoid disappointing them. In a treatment where trust choices were determined by a lottery, neither reciprocation nor beliefs responded to the opportunity cost, suggesting intention as a key mechanism. In another treatment, where trustees made choices conditional on each possible belief of the matched trustor, their reciprocation was responsive neither to opportunity cost nor to belief, providing no evidence for guilt aversion.