Hierarchical Context Guides Human Memory Search

A fundamental property of human memory is its ability to organize a continuous stream of information into discrete, searchable events. Although empirical work supports hierarchical memory representations in the brain, we lack a formal theory of how humans search this structure. Here, we present a hierarchical model of memory search that unifies a wide range of phenomena under a single framework. By tracking mental contexts at multiple levels, the model captures memory behavior across different timescales, from recalling single lists of information to navigating materials consisting of a series of lists. It explains enhanced recall at list boundaries by proposing a top-down hierarchical search: higher-level contextual cues are retrieved before activating lower-level item information. This mechanism also accounts for recall transition patterns across list boundaries, reproducing effects observed in the event memory literature. Taken together, these results provide a unified account of how humans efficiently organize and search their memories.