The relationship between lexical sophistication and independent and source-based writing

Lexical sophistication is an important component of writing proficiency. New lexical indices related to range, n-gram frequency, psycholinguistic word information, academic language, polysemy, and hypernymy have yielded new insights into the construct of lexical sophistication and its relationship with second language (L2) acquisition and writing. For example, recent studies have suggested that range and bigram indices are stronger indicators of lexical sophistication than frequency in the context of L2 acquisition and L2 writing and speaking proficiency. This study explores the relationship between these newly developed indices of lexical sophistication and holistic scores of writing proficiency in both independent and source-based writing tasks. The results suggest that range and bigrams are important predictors of essay quality in independent tasks, but that lexical sophistication indices are not strong predictors of essay quality in source-based tasks. The results also indicate that responses to source-based tasks tend to include more sophisticated lexical items than responses to independent tasks. Implications for second language writing assessment and pedagogy are discussed.