Temporal compression of naturalistic events in episodic memory: Effects of environmental familiarity and action involvement

Episodic memories are temporally compressed summaries of past experience, with the degree of compression varying with event characteristics. This study examined how two such characteristics—environmental familiarity and action involvement—influence temporal compression, objective recall content, and subjective memory quality. Across three experiments, participants viewed first-person videos of navigation (walking) in familiar or unfamiliar places, with goal-directed action videos (e.g., buying a notebook) also included in two of the experiments. Participants then mentally replayed each video to derive a compression measure, alongside subjective ratings and recall descriptions. Action involvement consistently reduced compression and enriched both subjective and objective aspects of remembering. Environmental familiarity effects on compression were context-dependent: absent when videos were recalled immediately after viewing (Experiment 1), present — with unfamiliar videos remembered in less compressed form — when familiarity was blocked across separate lists (Experiment 2), and eliminated when familiar and unfamiliar videos were mixed within the same lists (Experiment 3). Familiar videos were nonetheless consistently rated as more detailed and easier to remember, independent of list composition. Overall, environmental familiarity shaped the subjective experience of remembering without altering objective recall content, revealing a partial dissociation between subjective and objective memory measures, whereas action involvement consistently benefited both, underscoring the structuring role of actions in event memory. These results are discussed in relation to schema-based encoding, working-memory resource, and scene-construction accounts of temporal compression.