Lexical Complexity as a Function of Task Type and Proficiency Level in the Speech Monologs of Iranian EFL Learners

Despite the abundance of research evaluating the effects of task complexity, task types, and planning on the complexity, accuracy, and fluency of the language produced by learners, most studies have focused on the syntactic aspect of complexity, with very few studies investigating the lexical part of complexity. Such studies explored the lexical performance of learners through using merely one measure of lexical complexity (namely diversity). The present study is an attempt to further explore the effects of task type and proficiency level on different aspects of lexical complexity of spontaneous speech monologs produced by intermediate and advanced Iranian EFL learners. To this end, 35 intermediate and advanced Iranian learners of English performed three different speaking tasks: an argumentation, a description and a narration task. The speech monologs were coded for three different aspects of lexical complexity: diversity, density, and sophistication. Two-way repeated-measures ANOVAs were conducted to evaluate the main effects of task type (the within-subjects variable) and proficiency level (the between-subjects variable) on lexical complexity. The results showed that task type and proficiency level both significantly affect lexical complexity in the participants’ task performance. The argumentation task yielded the highest scores for diversity and density, while the highest sophistication score was obtained for the narration task. There was no interaction between task type and proficiency level for the diversity and sophistication scores, and the advanced learners consistently got higher diversity and sophistication scores for all the three tasks, while there was an interaction between the two variables for the density scores; the advanced learners got higher density scores for the description and narration tasks but not on the argumentation task.