Two experiments are reported that examined the temporal structure of recall for categorizable word lists by younger and older adults. All participants showed response bursting, in which recall order is clustered by semantic category, with longer interresponse times (IRTs) appearing between categories than within categories. Experiment 1 demonstrated that older adults, even when matched to younger adults in overall accuracy, differed in the rate of increase of between-category IRTs with output

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... sition, but not in within-category IRTs. Experiment 2 showed that this interaction is eliminated when the names of the response categories are provided to the participants. Results are interpreted in terms of combined effects of an age-compromised episodic memory system (betweencategory IRTs) accompanied by a comparatively preserved semantic system (within-category IRTs) in healthy aging.