Remembering an event typically takes less time than experiencing it, suggesting that episodic memory represents past experience in a temporally compressed way. Little is known, however, about how the continuous flow of real-life events is summarised in memory. Here we investigated the nature and determinants of temporal compression by directly comparing memory contents with the objective timing of events as measured by a wearable camera. We found that episodic memories consist of a succession of moments of prior experience that represent events with varying compression rates, such that the density of retrieved information is modulated by goal processing and perceptual changes. Furthermore, the results showed that temporal compression rates remain relatively stable over one week and increase after a one-month delay, particularly for goal-related events. These data shed new light on temporal compression in episodic memory and suggest that compression rates are adaptively modulated to maintain current goal-relevant information.

Although healthy aging has been related to a decline in recollection as indexed by objective measures, the subjective experience of recollection sometimes remains stable. To date, however, these age-related differences have only been examined using aggregated data across trials. In the current study, we investigated the relationship between subjective and objective measures of recollection on a trial-by-trial basis to determine whether the magnitude of this relationship was similar in young and older adults. Young and older participants were presented with pictures that were associated with descriptive labels at encoding. At retrieval, they were cued with the labels and were asked to rate the vividness of their memory for the associated picture and to recall as many details of the picture as possible. On average, older adults assigned higher vividness ratings but recalled fewer episodic details than young adults. Mixed-effects modeling revealed that the relationship between subjective (vividness) and objective (number of recalled details) recollection across trials was stronger in young than in older participants. These findings provide evidence that older adults not only retrieve fewer episodic details but also rely on these details to a lesser extent than young adults for judging the subjective quality of their memories.

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The age-related associative memory deficit can be alleviated, under some conditions, when to-beremembered associations are semantically related. In this study, we explored the experimental conditions in which older adults benefited from semantic relatedness and those that hindered any associative memory improvement. We did so by manipulating the level of semantic support within the associations presented at encoding and within the recombined pairs (i.e., the lures) at retrieval, such that pairs with high semantic support at encoding were recombined into pairs with equally high or with lower level of semantic support, and vice versa. We predicted that semantic relatedness would benefit older adults' associative memory when there was a decrease in semantic support from encoding to retrieval. Conversely, older adults' associative memory would be hindered when a recombination was equally or more familiar than the studied association. In Experiment 1, we manipulated the presence versus absence of semantic relatedness within associations both at encoding and at retrieval. In Experiment 2, we manipulated the frequency of related associations at encoding and at retrieval. Taken together, the results showed that older adults' associative memory was better in conditions in which associations closely matched semantic knowledge at encoding and were recombined into associations with no or less semantic support at retrieval. In contrast, older adults' performance was worse for semantically poorer associations at encoding, that were recombined into associations with greater semantic support at retrieval. This suggests that older adults' associative memory can be improved by semantic support under specific experimental conditions only.

While age differences in episodic memory are well documented, the impact of age on the structure of memories for real-world events has not been investigated in detail. Recent research has shown that the continuous flow of information that constitutes daily life events is compressed in episodic memory, such that the time needed to mentally replay an event is shorter than the actual event duration. To examine whether this process of temporal compression of prior experience in episodic memory is affected by aging, we asked young and older adults to engage in a series of events that simulated daily life activities while their experience was automatically recorded using a wearable camera. Subsequently, participants were asked to mentally replay these events in as much detail as possible and then to verbally report recalled contents and to rate the subjective qualities of their memories. Results revealed that the rates of temporal compression of events during mental replay were similar in young and older adults. In both age groups, rates of temporal compression were predicted by the density of recalled moments of prior experience per unit of time of the actual event duration. Interestingly, however, the number of recalled moments predicted the subjective vividness of memories in young but not in older adults. Taken together, these results suggest that the process of temporal compression of events in episodic memory is unaffected by age but that the subjective experience of memory vividness becomes less tied to recalled moments that represent the unfolding of events.