Masked morphological priming tracks the development of a fully mature lexical system in L2
Visual word identification is based on an early morphological analysis in one’s native language; how these mechanisms apply to a second language is much less clear. We recruited L1 Italian–L2 English speakers in a masked priming task where the relationship between prime and target was morphologically transparent, e.g., employer–EMPLOY, morphologically opaque, e.g., corner-CORN, or merely orthographic, e.g., brothel–BROTH. Critically, participants underwent a thorough testing of their lexical, morphological, phonological, spelling and semantic proficiency in their second language. By exploring a wide spectrum of L2 proficiency, we showed that this factor critically qualifies L2 priming. Genuine morphological facilitation only arises as proficiency grows; and opaque and orthographic priming shrink as L2 competence increases. Age of acquisition was also evaluated, and did not affect the priming pattern. Furthermore, we showed that L2 priming is modulated by sensitivity to probabilistic relationships between form and meaning. Overall, these data illustrate the trajectory towards a fully consolidated L2 lexicon, and show that masked priming is a key tracker of this process.