Probing the Origins of Subjective Confidence in Source Memory Decisions in Young and Older Adults: A Sequential Sampling Account

Subjective confidence is an important factor in our decision making, but how confidence arises is a matter of debate. A number of computational models have been proposed that integrate confidence into sequential sampling models of decision making, in which evidence accumulates across time to a threshold. An influential example of this approach is the relative balance of evidence hypothesis, in which confidence is determined by the amount of evidence for the choice that was made compared to the evidence for all possible choices. Here, we modify this approach by mapping distance from a decision threshold to confidence via a sigmoid function. This allows for individual differences in bias toward lower or higher levels of confidence, as well as sensitivity to differences in evidence between choices. We apply several variants of the model to assess potential age differences between young and older adults in source memory decision making in an existing data set (Dodson, Bawa, & Slotnick, 2007). We compare our model to the relative balance of evidence approach, and the results indicate that the sigmoidal method substantially improves model fit. We also consider models in which memory errors can arise from a misrecollection process that involves associating items with the incorrect source, a process that has been proposed to account for age differences in source memory confidence and accuracy, but find no evidence that misrecollection is necessary to account for the results. This work provides a viable model of subjective confidence that is integrated with well-established models of decision making and provides insights into effects of aging on source memory decisions. Public Significance Statement This study presents a theory of how subjective levels of confidence in memory decisions are determined in young and older adults by comparing evidence for different choice options. The findings suggest that the way confidence is calculated differs between people and may change across the lifespan