Lifespan accumulated differences in semantic memory structure contribute to increases in episodic false memories

Semantic memory grows across the lifespan with experience, scaffolding episodic memory processes while potentially contributing to memory errors when memory representations overlap. Prior work has attributed age-related increases in false recognition memory to executive dysfunction, but little is known about how lifelong semantic knowledge accumulation affects these episodic errors. In the current study, we recorded EEG while younger (n = 36) and older adults (n = 41) completed an episodic memory task in which study list-lure similarity was systematically varied using distributional model-derived measures of semantic similarity. We found older adults’ endorsement of lures was less dependent on semantic similarity than those of younger adults. Older adults also demonstrated reduced coupling of neural similarity to model-derived semantic similarity, and reduced encoding-retrieval reinstatement for accurate lure rejections. Together, these findings suggest that age-related increases in false memory reflect both altered semantic representational structure and reduced source monitoring, highlighting how semantic knowledge accumulated across the lifespan may simultaneously support episodic memory while increasing susceptibility to semantically driven distortions.