Narratives bridge the divide between distant events in episodic memory

Abstract

Many studies suggest that information about past experience, or episodic memory, is divided into discrete units called “events.” Yet we can often remember experiences that span multiple events. Events that occur in close succession might simply be linked because of their proximity to one another, but we can also build links between events that occur farther apart in time. Intuitively, some kind of organizing principle should enable temporally distant events to become bridged in memory. We tested the hypothesis that episodic memory exhibits a narrative-level organization, enabling temporally distant events to be better remembered if they form a coherent narrative. Furthermore, we tested whether post-encoding memory consolidation is necessary to integrate temporally distant events. In three experiments, participants learned and subsequently recalled events from fictional stories, in which pairs of temporally distant events involving side characters (“sideplots”) either formed one coherent narrative or two unrelated narratives. Across participants, we varied whether recall was assessed immediately after learning, or after a delay: 24 hours, 12 hours between morning and evening (“wake”), or 12 hours between evening and morning (“sleep”). Participants recalled more information about coherent than unrelated narrative events, in most delay conditions, including immediate recall and wake conditions, suggesting that post-encoding consolidation was not necessary to integrate temporally distant events into a larger narrative. Furthermore, post hoc modeling across experiments suggested that narrative coherence facilitated recall over and above any effects of sentence-level semantic similarity. This reliable memory benefit for coherent narrative events supports theoretical accounts which propose that narratives provide a high-level architecture for episodic memory.

Building bridges: the hippocampus constructs narrative memories across distant events

“…Although some models have suggested that semantic relatedness can determine whether words or sentences become integrated in memory (e.g. Reder & Anderson, 1980), we found that the memory advantage for coherent narrative events was over and above any advantage that could be observed at the word or sentence level (Cohn-Sheehy et al, 2021). Our findings suggested that episodic memory might be organized at a level above and beyond individual words, sentences, or events, on the basis of narrative coherence: the degree to which individual units of information can be interrelated within a single narrative representation (Bartlett, 1932;Graesser et al, 1994).…”

“…The ability to organize events into a narrative can be beneficial for memory (Bransford & Johnson, 1972;Kintsch, 1992;Rumelhart, 1977;Thorndyke, 1977;Trabasso et al, 1984). For example we recently demonstrated that, when temporally separated events could be assimilated into a narrative, they were recalled in greater detail than overlapping events involving the same character in different narratives (Cohn-Sheehy et al, 2021). Furthermore, narratives are more than the semantic information conveyed in words and sentences alone (Graesser et al, 1994;Kintsch, 1992;Trabasso et al, 1984;van Dijk & Kintsch, 1983).…”

“…Recent models have attempted to describe the conditions under which the hippocampus supports memory integration versus differentiation (Chanales et al, 2017(Chanales et al, , 2019Horner et al, 2015;Kumaran, 2012;Ritvo et al, 2019). These models generally focus on simple associations between items and do not address any role for narrative coherence-though, as our recent behavioral findings suggest (Cohn-Sheehy et al, 2021), the ability to form a narrative might determine whether or not events become integrated in memory.…”

“…For example, you might subsequently encounter Sandra at a café, slapping an unnamed man as she walks out. Although Sandra appears in temporally separated events, they coalesce to form a narrative: a larger unit of information which encompasses multiple events, and in which one's understanding of each event is dependent on information from other events (Bartlett, 1932;Cohn-Sheehy et al, 2021;Graesser et al, 1994;Trabasso et al, 1984;van Dijk & Kintsch, 1983;Willems et al, 2020).…”

Narrative thinking lingers in spontaneous thought

“…The finding that deeply processed stories linger in mind (immediately after an experience) is also consistent with the behavioural finding that stories and situations persist in the form of lasting memories. Information presented in story form is better remembered than non-narrativized information (37), narrative coherence benefits memory for naturalistic events (38), and the act of studying a word-list as if it were a story markedly improves recall (39) (for review, see (40)). Beyond improving memory, stories also have lasting consequences on how we behave and what we believe (41)(42)(43)(44).…”