cognitive task complexity and iranian efl learners’ written linguistic performance across writing proficiency levels

recently tasks, as the basic units of syllabi, and the cognitive complexity, as the criterion for sequencing them, have caught many second language researchers’ attention. this study sought to explore the effect of utilizing the cognitively simple and complex tasks on high- and low-proficient efl iranian writers’ linguistic performance, i.e., fluency, accuracy, lexical complexity, and structural complexity. at first, based on their scores on the writing test of tofel (2003), participants were assigned to high- and low-proficient writers. participants in both groups first accomplished the simple task which was the narration of a story based on a set of pictures. one week later, they were asked to perform the complex task which was writing about a topic requiring reasons. then the written productions were encoded on the measures of fluency, accuracy, lexical complexity, and structural complexity. four two-way mixed-design anovas were conducted. the results revealed that the learners significantly generated less accurate, more structurally complex, and more fluent language in the complex task. no significant effect was found for the lexical complexity measure. the high-proficient group performed significantly better in the four measures. the interaction between task complexity and writing proficiency did not yield any significant results. on the whole, based on the findings, the ‘limited attentional model’ was shown to be more accurate in comparison with ‘cognition hypothesis’ and the ‘threshold level hypothesis’ was not confirmed.