Organizational Dynamics of Memory Across Days

When individuals repeatedly study and recall information across multiple learning trials their responses exhibit increasing levels of subjective organization. Whereas classic studies investigated the evolution of organization across lists within the short-time span of a single session, here we ask how memory changes over many days. Specifically, we examine how semantic, temporal, and subjective organization during a recall period shapes memory after days of intervening cognitive activity. Analyzing data from two multi-session free recall experiments, we find that subjects demonstrate a strong tendency to cluster recalls based on previous output order, with this effect strengthening across sessions. In line with the idea that thoughts become memories, we show that even false memories produced on a given session tend to re-occur on subsequent days. Our results attest to the crucial role that retrieval plays in shaping long-term episodic memory.