A multidimensional approach to assessing the effects of task complexity on L2 students’ argumentative writing

The issue of how manipulating task-design factors may impact second language writing needs further exploration. In this study, task complexity was manipulated by changing the number of argument elements and reasoning demands within two argumentative writing tasks. This study firstly triangulated three sources of data (i.e., dual-task methodology, expert judgements, and post-task questionnaire) to offer separate evidence for validating the putative task-complexity manipulations. Results obtained by the three measures consistently supported the efficacy of the task-complexity manipulations; that is, the complex task version, as intended, was more cognitively demanding than the simple version. Next, 65 Chinese L2 learners were recruited to examine the effects of the verified task complexity on their writing performance. Learners’ writing was multidimensionally assessed in terms of syntactic complexity, lexical complexity, accuracy, fluency, and functional adequacy. The results showed no significant differences in syntactic complexity, accuracy, or fluency between the simple and complex tasks, although an increasing tendency occurred in the mean values of accuracy. Increasing task complexity led to a decrease in lexical complexity and functional adequacy, which supports the Limited Attentional Capacity Model that learners with a limited and single-resource attentional capacity prioritize their attention when limits are reached. The findings underline the importance of validating task complexity of the writing tasks for teaching and assessing writing and providing guidance for teachers and test designers on grading and sequencing tasks. Theoretical and methodological implications are also discussed.