Different topics, different discourse: Relationships among writing topic, measures of syntactic complexity, and judgments of writing quality

• Topic affects syntactic complexity of ESL writing.
• Topic plays a role in the relationship between syntactic complexity and writing quality.
• Global-level syntactic complexity positively correlates with scores across topics.
• Local-level syntactic complexity may not correlate with scores across topics.
• Variety of complex structures used is associated with higher ESL writing quality.

This study examined the relationship between syntactic complexity of ESL writing and writing quality as judged by human raters, as well as the role of topic in the relationship. Syntactic complexity was conceptualized and measured as a multi-dimensional construct with interconnected sub-constructs. One hundred and ninety ESL graduate students each wrote two argumentative essays on two different topics. It was found that topic had a significant effect on syntactic complexity features of the essays, with one topic eliciting a higher amount of subordination (finite and non-finite) and greater global sentence complexity and the other eliciting more elaboration at the finite clause level (in particular, coordinate phrases and complex noun phrases). Local-level complexity features that were more prominent in essays on one topic (i.e., subordination and elaboration at the finite clause level) tended not to correlate with scores for that topic. Rather, a reversed pattern was observed: the less prominent local-level complexity features for essays on one topic tended to have a stronger correlation with scores for that topic. Regression analyses revealed global sentence and T-unit complexity as consistently significant predictors of scores across the two topics, but local-level features exhibited varied predicting power for scores for the two topics.