Dynamic assessment of L2 argumentative writing: Understanding the effectiveness of ZPD-based instructional enrichment

Argumentative writing has long been recognized as challenging for English second language (L2) writers yet central to their academic success in educational settings. This article investigates the effectiveness of a writing instructional enrichment program informed by diagnoses from dynamic assessment (DA) in promoting L2 learners’ argumentative writing abilities. Grounded in Vygotskian Sociocultural Theory, DA introduces mediation into the assessment procedure, so that learner emerging abilities are diagnosed through observing their responsiveness to mediation when difficulties arise. In this study, prior to and following the instructional programs, a three-step, interactionist DA procedure was implemented where participants composed argumentative essays in response to reading–writing integrated tasks. Following the initial DA procedure, participants were assigned to either an enrichment program that received individualized instruction on integrated argumentative writing targeting their Zone of Proximal Development (ZPD), or a non-enrichment program, where generic and standard instruction uninformed by DA diagnoses was provided. Finally, the study implemented a transfer assessment to ascertain the participants’ ability to transfer their learning to a more challenging, complex integrated task. The essays completed independently by both enrichment and non-enrichment groups during the assessments were analysed in terms of stance taking and stance support. Stance taking was examined through writers’ establishment of their own position and their engagement with opposing positions, whereas stance support was investigated in four sub-aspects: type of evidence, number of source ideas, non-transgressive/transgressive intertextuality, and content accuracy. The findings revealed that the enrichment group outperformed the non-enrichment group in stance taking and stance support at both the DA procedure implemented following the writing instructional programs and the transfer assessment. The article concludes by highlighting the effectiveness of tailoring writing instruction towards learners’ ZPD as diagnosed through DA in promoting their development of integrated argumentative writing.