Adaptive memory: Source memory is positively associated with adaptive social decision making.

The key insight behind the adaptive memory framework is that the primary function of remembering is not to help us to relive the past but to inform adaptive behavior in the future. However, the beneficial effects of memory on the individual's fitness are often difficult to study empirically. In the case of social cooperation, it is comparatively easy to derive testable predictions about the relationship between specific types of memory (e.g., source memory) and specific types of adaptive decision making (e.g., direct reciprocity). In the present study, we examined both the participants' behaviors in a Prisoner's Dilemma game and their memory performance in a source-monitoring test. Participants showed evidence of adaptive decision making. Their willingness to cooperate was strongly determined by their partners' behaviors in previous rounds. Individual parameter estimates of old-new recognition, source memory, and guessing were obtained via hierarchical multinomial processing tree modeling. Source memory was positively associated with adaptive decisions in the Prisoner's Dilemma game. The better participants' source memory, the more often they cooperated with cooperators and the less often they cooperated with cheaters. Guessing in the memory test, by contrast, was unrelated to cooperation. The results underline the importance of source memory in adaptive decision making.