Abstract
Our experiences in the world support memories not only of specific episodes but also of the generalities (the 'gist') across related experiences. It remains unclear how these two types of memories evolve and influence one another over time. In two experiments, 173 human participants encoded spatial locations from a distribution and reported both item memory (specific locations) and gist memory (center for the locations) across 1-2 months. Experiment 1 demonstrated that after 1 month, gist memory was preserved relative to item memory, despite a persistent positive correlation between them. Critically, item memories were biased toward the gist over time. Experiment 2 showed that a spatial outlier item changed this relationship and that the extraction of gist is sensitive to the regularities of items. Our results suggest that the gist starts to guide item memories over longer durations as their relative strengths change.
Highlights
Our experiences in the world are perceived and remembered both as individual items, events, and episodes, and as aggregated collections or sets of related items with common properties
All three delay groups performed above chance on both the item memory test and the gist memory test at both Session 1 and 2
We demonstrated that the accuracy of item memory decreased more compared to the accuracy of gist memory over time, though there was a persistent positive correlation between these them
Summary
Our experiences in the world are perceived and remembered both as individual items, events, and episodes, and as aggregated collections or sets of related items with common properties. Studies of long-term memory in both humans and animals have demonstrated that gist memory persists or even improves over time, whereas memory for the individual items from which the gist is built fades (Posner & Keele, 1970; Richards et al, 2014). What do these observations of temporal dissociations tell us about the relation between item memory and gist memory? A persisting gist memory with less accurate item memory is not sufficient evidence for the independence of a gist representation: Even when item memories become noisy and less accurate, they still can retain enough information to support a relatively intact memory of gist at retrieval (Alvarez, 2011; Squire, Genzel, Wixted, & Morris, 2015)
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