Influence of word age-of-acquisition, vocabulary size, formal-lexical similarity and semantic richness of words on lexical recognition and production: A study on foreign-word training.

This article investigates the age-of-acquisition (AoA) effect—the phenomenon where words learned earlier are accessed more quickly than later-learned words—by examining how vocabulary size, formal-lexical similarity (neighbourhood density), and semantic richness (number of meanings) influence AoA in lexical recognition and production. Through three controlled laboratory experiments with Spanish-speaking participants learning Welsh words, the study found that vocabulary size showed a marginal modulatory effect on AoA in lexical decision accuracy, formal-lexical similarity did not affect AoA, and semantic richness modulated AoA effects in a task-dependent manner: AoA effects appeared only for two-meaning words in lexical decision and only for one-meaning words in picture naming. Overall, the results provide mixed evidence for AoA effects, primarily supporting the mapping hypothesis—which attributes AoA to the arbitrary connections between word forms and meanings—while challenging some predictions of the semantic hypothesis and integrated accounts. These findings highlight the complex interplay of lexical and semantic factors in word learning and processing, with implications for understanding AoA effects in both first and second language acquisition contexts.