What divides and unites our memories: multi-factor trial-wise predictions of memory across 6+ million trials

A majority of memory research examines a single or a few factors that influence memory, but a broader perspective is needed to form a comprehensive understanding of the mechanisms of memory. Broadly, prior work has largely focused on observer effects (e.g., individual differences, internal states) and environmental effects (e.g., task, context), with only more recent work focusing on item effects (e.g., the typicality or memorability of stimuli). Here, I analyze 6,223,953 memory decisions made by 13,946 participants on a continuous recognition task for 26,107 naturalistic object images to test how these different factors influence long-term episodic memory. The individual subject and the memorability of the stimulus emerge as the most important factors for predicting successful hits, with surprisingly little influence of the experimental context. In contrast, while less variance is captured by these factors for false alarms, a wider variety of factors are important, including image factors, observer factors, and experimental context. These results suggest that much of what drives our memory is shared and predictable, and demonstrate the need for more research that focuses on multiple factors simultaneously in more representative and naturalistic tasks.