Exploring whether and when acquisition order interacts with exposure frequency during lexical learning: Evidence from behavioral and electrophysiological findings

Production and comprehension research has shown that words acquired earlier and encountered more frequently are responded faster and more accurately, reflecting the effects of age of acquisition (AoA) and word frequency (WF). Both effects are interpreted as the quality of lexical-semantic/phonological representations and the structure of lexical network. However, it remains unclear how the processing advantages associated with earlier acquisition and frequent occurrence develop in the vocabulary learning. To address these issues, this study investigated whether and how acquisition order and exposure frequency of to-be-learnt pseudowords, mirroring AoA and WF of real words, affect Chinese spoken word production over four consecutive days. ERP recordings on Day4 further explored the time courses of acquisition order and exposure frequency effects for newly-acquired pseudowords. Results illustrated an overall benefit of earlier acquisition regardless of the degree of consolidation, while higher exposure frequency merely modulated early formation of episodic representations. Moreover, the acquisition order effect was localized to more positive waveforms occurring around 148–578 ms after pictures onset. No interaction was observed between acquisition order and exposure frequency at either behavioral or electrophysiological levels. Our findings therefore have implications for the dominant role of acquisition order over exposure frequency in shaping the development of lexical network in adults.