Flexibility in the recall of autobiographical memories, from highly detailed and unique episodes to more abstract and decontextualised personal knowledge, depends on control processes and contextual factors, including the specific task demands. Here, we investigated the costs of switching between different types of autobiographical retrieval in young and older adults. In the task, participants were asked to recall specific (unique events) and categoric events (repeated events) in separate blocks of trials, and were then instructed to switch between specific and categoric retrieval. We analysed autobiographical memory recall in term of accuracy (percentage of memories consistent with instructions), and elaboration (count of different types of details produced). Our results revealed switch costs in memory accuracy, with older adults recalling fewer memories consistent with instructions after a switch occurred, but no age differences in accuracy at baseline, when specific and categoric memories were retrieved in separate blocks. Age difference in memory elaboration were identified, with older adults producing a lower proportion of episodic details when instructed to describe specific past events, as well as a lower proportion of repeated event details and a higher proportion of semantic details when instructed to retrieve categoric memories. Together these results reveal that autobiographical memory retrieval in ageing is highly dependent on the specific task demands, intertwined with a general episodic-to-semantic shift.

Most measures of naturalistic human memory instruct participants to recall personally-experienced episodes in narrative format. These narratives contain non-episodic details, such as general knowledge of the world, or personal knowledge about one’s life circumstances that are elevated with aging. As this non-episodic content is incidental to the instructions, it is difficult to interpret. We modified the widely used Autobiographical Interview (AI) to create a Semantic Autobiographical Interview (SAI) that explicitly targets personal semantic (P-SAI) and general semantic memories (G-SAI). We tested the SAI in young and older adults, alongside with the original AI. Older adults produced a higher proportion of off-task utterances (i.e., details not probed by instructions) across all sections of the interview. Specifically, older adults produced more autobiographical facts in the AI, more episodic and general semantic details in the P-SAI, and more self-knowledge in the G-SAI than did young adults. However, older adults also consistently produced more probed autobiographical facts than did young adults on the P-SAI. These findings suggest that the increased production of semantic details in ageing reflects a bias towards age differences in autobiographical recall that goes beyond episodic remembering, as reflected by an age-associated abundance of semantic details across sections of the interview, findings that are not accommodated by accounts of aging and memory emphasizing reduced cognitive control or compensation for episodic memory impairment.

A cardinal feature of episodic memory is the ability to generalize knowledge across similar experiences to make inference about novel events. Here, we tested if this ability to apply generalized knowledge exists for experiences that are similar in terms of underlying concepts, prior knowledge, and if this comes at the expense of another feature of episodic memory: forming detailed recollection of events Over three experiments, healthy participants performed a modified version of the acquired equivalence test in which they learned overlapping object-scenes associations (A-X, B-X and A-Y) and then generalized the acquired knowledge to indirectly learned associations (B-Y) and novel objects (C-X and C-Y) that were from the same conceptual category (e.g. A - pencil; B - scissors) and different categories (e.g. A - watch; B - fork). In a subsequent recognition memory task, participants made old/new judgements to old (targets), similar (lures) and novel items. Across all experiments, we found that indirect associations that were rooted in conceptual similarity knowledge led to higher rates of generalisation but reduced detailed object memory. Our findings suggest that activating prior conceptual knowledge emphasizes the generalization function of episodic memory at the expense of detailed recollection. We discuss how this trade-off between generalization and recollection functions of episodic memory result from engaging different representations during learning.