Dissociating the time courses of age of acquisition effect and word frequency effect during Chinese spoken word production.

Comprehension and production research robustly demonstrates a processing advantage of early-acquired and more frequent words than late-acquired and infrequent words separately. Because age of acquisition (AoA) and word frequency (WF) are correlated in nature, to what extent both factors jointly and independently affect speech production remains unclear. This study aimed to investigate underlying mechanisms behind AoA and WF effects in Chinese spoken word production with electrophysiological measures. We orthogonally manipulated AoA and WF to examine when and how these variables jointly affect spoken production. Results illustrated an interaction between AoA and WF in a time window of conceptual preparation (around 78-170 ms after picture onset) and subsequently an independent AoA effect at lexical selection (240-322 ms) and a WF effect at phonological encoding (462-566 ms). Our findings therefore provide supports for interactive and isolated origins for AoA and WF effects in speech production.