AoA effects in reading aloud and lexical decision: Locating the (semantic) locus in terms of the number of backward semantic associations

In the present study, we analyse data from the English Lexicon Project to assess the extent to which age of acquisition (AoA) effects on word processing stem from the number of semantic associations tied to a word. We show that the backward number of associates (bNoA; that is, the log transformed number of words that produce the target word in free association) is an important predictor of both lexical decision and reading aloud performance, and reduces the typical AoA effect as represented by subject ratings in both tasks. Although the AoA effect is reduced, it remains a significant predictor of performance above and beyond bNoA. We conclude that the semantic locus of AoA effects can be found in the number of backward connections to the word, and that the independent AoA effect is due to network plasticity. We discuss how computational models currently explain AoA effects, and how bNoA may affect their processing.