Are There Age Differences in Consolidated Episodic Memory?

Background/Study Context: While most aging research on memory uses a retention interval of one hour or less, episodic consolidation takes longer (e.g., 6-24 hours for synaptic consolidation). In three experiments, we examined age differences in recall followed by recognition in which the retention interval was varied in younger and older adults.

In Experiment 1 (n = 24 for both age groups), zero-, 1- and 24-hour retention intervals were used for recall for all participants, and a 24-hour retention interval was used for recognition. In Experiment 2 (n = 24 for both age groups), just a 24-hour retention interval was used. In Experiment 3 (n = 20 for both age groups), a within-subjects design was used in which participants recalled one word list after one hour and again after 24 hours, and recalled another word list just after 24 hours (with recognition for both conditions after the 24-hour recall).

In Experiment 1, older adults recalled fewer words at both the 1- and 24-hour retention intervals, but the magnitude of the age difference did not differ. In Experiment 2 (just 24-hour retention interval), there were no age differences in recall. In Experiment 3, in the two-recall condition, older adults showed lower recall at both 1-hour and 24-hour retention intervals (but the magnitude of the age difference remained constant across retention interval). In the single-recall just 24-hour retention condition, there were no age differences. There were no age differences in recognition in any of the three experiments.

These results suggest that recall declines for a 24-hour retention interval relative to a zero or one-hour retention interval (Experiments 1 and 3) for both age groups. However, when the first recall attempt occurs after a 24-hour retention interval, there are no age differences. These replicated results suggest that older adults do not benefit as much as younger adults from pre-consolidated rehearsal, but that rehearsal-based age differences do not increase in magnitude from the last rehearsal to memory consolidation. Furthermore, (along with), the present results indicate that there are no age differences in recall when the first recall attempt occurs after a long retention interval - when memory consolidation is likely to have occurred before the first retrieval attempt.