The effects of event structure and duration on the temporal compression of daily life activities in episodic memory

Mentally replaying past events (e.g., having breakfast, doing the laundry) generally takes less time than the actual event duration, a phenomenon known as the temporal compression of events (TCE) in episodic memory. In this study, we evaluated the extent to which rates of TCE depend on the structure and duration of events by manipulating both dimensions orthogonally. Thirty-seven participants were presented with movie clips of everyday activities that lasted 30 or 60 s and that included few or many event boundaries (EBs; moments within activities corresponding to the transitions between sub-events). For each movie, participants had to mentally replay the unfolding of the event they just watched in as much detail as possible. TCE was computed as the ratio between the actual event duration to the duration of mental replay. Results showed that TCE was higher for long than short movies and for movies that contained few EBs. In addition, there was a significant interaction between event structure and duration, showing that the TCE difference between long and short movies was smaller when the number of event boundaries was high. These results are consistent with the view that the unfolding of events is represented in episodic memory as a succession of experience units that are formed by the perception of EBs. With increased temporal distance between EBs, the experience units encoded in episodic memory would fail to include the entire segment duration between EBs, leading to temporal discontinuities in the representation of the event’s unfolding and consequently higher TCE.