Derivational Morphology in L2 English: Investigating the Role of Affixal Neutrality Through the Lens of Linguistic Theory

This study investigates how second language (L2) learners acquire morphologically complex English words, focusing on affixal neutrality—whether suffixes preserve the phonological form and semantic transparency of the base (e.g., -ness in happiness) or trigger phonological/orthographic changes (e.g., -ity in activity). Drawing on linguistic theories of morphological decomposition and lexical representation, we examine how this property influences different dimensions of derivational knowledge. Fifty-four Mandarin-speaking secondary school EFL learners completed three receptive tasks targeting relational knowledge (morphological relatedness), syntactic knowledge (category awareness), and distributional knowledge (contextual appropriateness). Lexical items varied in affixal neutrality, and participants’ accuracy and response times were analysed across three L2 proficiency levels. Affixal neutrality significantly affected performance in the relational knowledge task, with neutral suffixes facilitating accuracy and faster responses. Effects were attenuated in syntactic and distributional tasks, suggesting domain-specific sensitivity to neutrality. L2 Proficiency was associated with higher accuracy across all three domains but did not substantially affect processing speed. These findings highlight the selective role of a theoretically motivated morphological property in L2 lexical acquisition and show how linguistic concepts such as affixal neutrality can form the basis of targeted hypotheses, bridging theoretical linguistics and empirical research in second language learning.