The temporal contiguity effect (TCE) is the tendency for the recall of one event to cue recall of other events originally experienced nearby in time. Retrieved context theory proposes that the TCE results from fundamental properties of episodic memory: binding of events to a drifting context representation during encoding and the reinstatement of those associations during recall. If these processes are automatic, the TCE should not be dependent on any encoding strategy and should, in fact, be present regardless of encoding intentionality. Here, we ask whether this theory is compatible with recent findings that the TCE is dramatically reduced under incidental encoding, even though memory accuracy is only modestly reduced. We begin by attempting to replicate this finding in a new large-scale study with over 5,000 participants in which we manipulated encoding intentionality between participants in both delayed free recall and continual distractor free recall. A small, but reliable, TCE was observed in all conditions, although the effect was dramatically reduced in incidental encoding. In a simulation study, we demonstrated that retrieved context theory can simultaneously account for both overall recall and the strength of the TCE in incidental encoding conditions. Additional analyses revealed that the incidental TCE is not an artifact of theoretically uninteresting factors, such as recency, and is consistent with being generated by the core contextual dynamics of retrieved context theory.

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Memory tends to be better when items are processed for their meaning (deep processing) rather than their perceptual features (shallow processing). This levels of processing (LOP) effect is well-replicated and has been applied in many settings, but the mechanisms involved are still not well understood. The temporal contiguity effect (TCE), the finding that recalling one event often triggers recall of another event experienced nearby in time, also predicts memory performance. This effect has given rise to several competing theories with specific contiguity-generating mechanisms related to how items are processed. Therefore, studying how LOP and the TCE interact may shed light on the mechanisms underlying both effects. However, it is unknown how LOP and the TCE interact—the various theories make differing predictions. In this preregistered study, we tested predictions of three theoretical explanations: accounts which assume temporal information is automatically encoded, accounts based on a trade-off between item and order information, and accounts which emphasize the importance of strategic control processes. Participants completed an immediate free recall task where they either engaged in deep processing, shallow processing, or no additional task while studying each word. Recall and the TCE were highest for no-task lists and greater for deep than shallow processing. Our results support theories which assume temporal associations are automatically encoded and those which emphasize strategic control processes. Both perspectives should be considered in theory development. These findings also suggest temporal information may contribute to better recall under deeper processing with implications in determining which situations benefit from deep processing.

Remembering one item in free recall often triggers recall of other items encoded nearby in time to the initial item. Retrieved Context Models can account for this temporal contiguity effect (TCE) but cannot account for how various experimental manipulations modulate the size of the TCE. We attempt to model the finding that orthographic distinctiveness dramatically reduces the TCE. Across six experiments, we found that the TCE is sometimes attenuated (though never eliminated) by distinctiveness. We developed a model of the distinctiveness effect by integrating the item-order framework with Retrieved Context Models. This model assumes orthographic distinctiveness increases the amount of processing devoted to items themselves, thereby reducing the functionality of the model mechanisms that generate temporal contiguity: context drift rate during study and the formation of new associations between items and experimental context. This model was fit to recall and TCE data from pure-list conditions and accounted for the data quite well. We then used the parameter values resulting from pure-list fits to simulate mixed-list data. Despite the substantial differences between pure- and mixed-lists, the model fit the mixed-list data quite well. The results support an item-order account of the distinctiveness effect.

In free recall, temporal information is often used to guide memory search, such that remembering one event tends to cue retrieval of other events that occurred nearby in time (temporal contiguity effect Kahana, 1996). Although temporal information may be automatically encoded (Mundorf et al., 2021), is it also automatically retrieved? We utilized repetition priming to determine if temporal information can influence implicit retrieval. Across 30 trials, subjects (n = 602) read words aloud as they appeared onscreen. In each trial, two words were repeated (cue and target). On their first presentation, the repeated words were separated by |lag| = 1, 2, or 5. On their second presentation, the cue was always presented first, immediately followed by the target. We found temporal contiguity in surprise final free recall, replicating previous work with incidental encoding and explicit retrieval. To test for temporal effects in implicit memory, we compared repetition priming for cue and target words, asking if repeating the cue facilitated processing of the target and if this facilitation varied depending on initial lag. The repetition priming effect was overall greater for targets than primes, demonstrating an implicit contiguity effect whose magnitude differed depending on initial lag.