Siros Izadpanah - English Language Department, Islamic AZAD University, Zanjan branch, Zanjan, Iran
Esmaeil Shajeri - English Language Department, Islamic AZAD University, Zanjan branch, Zanjan, Iran

Based on Robinson’s Cognition Hypothesis, this study explored the effects of task complexity on the lexical complexity of Iranian EFL students’ argumentative writing.This study was designed to explore the manipulation of cognitive task complexity along +/-single task dimension (a resource dispersing dimension in Robinson’s triadic framework) on Iranian EFL learners’ production in term of lexical complexity. To this end, based on the results of the writing test of TOFEL (۲۰۰۴), ۴۸ learners were selected and assigned to two groups, simple task group (STG, n = ۲۴) and complex task group (CTG, n= ۲۴) randomly. The participants in the STG were given an eight-frame picture which had been arranged in the correct sequence before its administration (+single task). These participants were required to order the frames in the right sequence first, before starting writing (- single task). Their output was encoded based on the measures of lexical complexity. The null hypothesis was nullified since the results indicated positive significant impact of +/-single dimension on lexical complexity. Regarding the results of the present study, it can be stated that when the participants were engaged putting the pictures in their correct order in the complex task, they carried out deeper semantic processing in order to find the reasonable order, which might lead to the better activation of their exemplar-based system and made them browse it more deeply. It was found that, at least in the Iranian context, Robinson’s (۲۰۰۵) predictions were more convincing.

Iranian EFL students, lexical complexity, +/-single task dimension, task complexity, triadic componential framework