Effects of task complexity on the fluency and lexical complexity in EFL students’ argumentative writing

Based on Cognition Hypothesis and Skehanʹs (1998) Limited Attentional Capacity Model, this study explored the effects of task complexity on the fluency and lexical complexity of 108 EFL students’ argumentative writing. Task complexity was manipulated using three factors: (1) availability of planning time; (2) provision of ideas and macro-structure; and (3) draft availability. All participants were randomly assigned to the above three factors in which the availability of the planning time factor had 4 levels (extended pre-task, pre-task, free-writing, and control); the provision of the ideas and macro-structure factor had 3 levels (topic, ideas, and macro-structure given; topic and ideas given; and topic given); and the draft availability factor had 2 levels (draft available vs. draft unavailable) using their writing task proficiency scores as a measure. Results showed that: (1) increasing task complexity, with respect to the planning time continuum, produced significantly greater fluency II (mean number of words produced per minute of the total time spent on the task) and lexical complexity; (2) increasing task complexity, through the provision of ideas and macro-structure, produced significantly greater lexical complexity but no effect on fluency I (mean number of words produced per minute of transcription) or fluency II; and (3) increasing task complexity, through draft availability, produced no significant differences in fluency and lexical complexity. Implications of these findings are discussed.