Linguistic complexity and writing proficiency in assessing L2 Spanish writing

Abstract Although linguistic complexity is widely used to assess second language (L2) writing proficiency, the linguistic correlates of L2 Spanish writing proficiency remain relatively underexplored. This study addresses this gap by examining how selected lexical, syntactic, and morphological complexity indices predict L2 Spanish learners’ standardized proficiency scores. We analyzed a corpus of 3,034 essays from L2 Spanish learners, utilizing their standardized placement test scores as a continuous measure of proficiency. A multiple linear regression model identified a concise set of complexity indices that effectively predicted proficiency scores, explaining a significant portion of the variance ( R 2 = .557). Results reveal a clear proficiency-based linguistic profile: advanced writing was significantly predicted by greater phrasal complexity, sustained clausal subordination, and higher lexical sophistication. In contrast, beginners’ writing was characterized by simpler syntactic strategies. These findings provide a robust, empirically derived profile of L2 Spanish writing development, offering valuable implications for pedagogical instruction, assessment rubrics, and automated evaluation tools.