Episodic memory abilities predict lexical diversity in spontaneous speech across languages and the adult lifespan

Abstract

Previous research has linked episodic memory to word learning and processing, but its role in broader lexical behaviors, such as lexical diversity, is still not well-understood. The present study leveraged existing data from a community-based sample of 564 adults (ages 27–89) who completed an episodic memory task and provided spontaneous speech in English or Spanish. Episodic memory abilities were measured on an immediate and delayed test and lexical diversity in spontaneous speech was measured using root type-token ratio and hapax legomena. Regression analyses revealed that both immediate and delayed memory scores were associated with lexical diversity metrics, even after adjusting for age, sex, education, and language, with small, yet largely consistent, overall effect sizes ranging from R ²  = .087 to R ²  = .122. These findings provide novel evidence that episodic memory contributes to the lexicon by supporting the flexible retrieval of diverse lexical items in natural speech. The results are consistent with recent theoretical accounts proposing that episodic memory continues to shape the mental lexicon throughout the lifespan.