How Memory Crystallizes the Past: Memories Become More Consistent Over Time Due to Differential, Nonconstant Change

Abstract

How do memories of real-life events change over time, and why do some aspects persist while others fade? We propose that two basic properties of memory-nonconstant change and differential decay across dimensions-jointly give rise to "crystallization," a process by which memories become increasingly stable and selected over time. Under the crystallization account, changes in all dimensions of memory occur disproportionately early, but different dimensions of memory change at different rates. Taken together, these processes lead to systematic transformations of memories over time. Across five studies, we examine how event memories evolve using the Memory Experiences Questionnaire (MEQ), a multidimensional measure that captures qualities such as vividness, coherence, emotional intensity, and sensory detail. We find that change is concentrated in the early period following an event and that dimensions associated with reliving-vividness, sensory detail, and coherence-decline more quickly than others. In three studies, we also find that, consistent with our account, multiple reports of the same event become more similar to each other over time. These findings extend existing theories of memory change and suggest a mechanism for the emergence of stable long-term representations from complex, multidimensional experiences.

Keywords: memory, temporal discounting, power functions