Revisiting the predictive power of traditional vs. fine-grained syntactic complexity indices for L2 writing quality: The case of two genres

This study investigated the extent to which traditional vs. fine-grained indices of syntactic complexity could predict second language (L2) raters’ quality ratings of 581 application letters and 595 argumentative essays produced by college-level Chinese English as a foreign language (EFL) learners. Our results showed that fine-grained indices explained a larger proportion of variance in both letter and essay quality than traditional indices. More importantly, however, our results revealed substantial genre effects on the explanatory power of traditional and fine-grained indices as well as on the specific types of indices that significantly predicted L2 writing quality. Furthermore, our results differed from previous findings with respect to the effect size of traditional indices for essay quality as well as the relative importance of fine-grained phrasal and clausal complexity indices in essay quality. These findings call for the need to systematically assess the predictive power of syntactic complexity indices across different genres.