IntroductionFor productby practicing language items. Besides, theybelieve that learners

IntroductionFor many years, researchers have been eagerto find out whether different levels of taskstructure and cognitive complexity have anynoticeable impact on learners’ oralproduction. This subject has always beencontroversial since the degree to adjust thetask, according to learners’ ability, has always attracted the researchers’ attention. There is general consensus on the claim that planning and other factors such as cognitivecomplexity of the task might have crucialimpact on oral production (Ahmadian, 2012;Ahmadian, 2011; Ellis, 2000;Skehan & Foster, 1996; Wendel, 1997; Ellis2003).  Jeon and Hahn (2006) express that taskbasedlanguage teaching has a substantialimplication for the area of languagelearning. They maintain that learning is adevelopmental process with the aim ofpromoting communication and socialinteraction rather than acquiring a productby practicing language items. Besides, theybelieve that learners learn the targetlanguage more effectively when they arenaturally exposed to meaningful task-basedactivities. Although early empirical studiesstrongly support the use of task as abeneficial way to conceptualize languageteaching, the amount of research in this areais still not sufficient. Preparing suitable tasksdemand a great deal of exploration in relatedstudies and a deep insight through theinfluence of the task type on learners’ oral   42                                                                                                    The effect of increase in task cognitive complexity production in terms of accuracy andlinguistic complexity. Therefore, the use oftask-based programs will be open to moreresearch (Skehan, 1998). According to Revesz (2011), taskcomplexity can affect attentional allocationand the focus on second language (L2)constructions during task performance, andthis can influence the quality of learning.However, there were some inconsistenciesamong the findings of applied linguisticsregarding the impact of task type onaccuracy and linguistic complexity. Tobridge the gap and to understand theimportance of selecting appropriate tasks, itis necessary to conduct more studies in thefield. Literature review   Since 1980, second language acquisition (SLA) researchers have been interested toexplore the impact of task cognitivecomplexity on oral production. A clearunderstanding of the load of cognitivedemands on participants can help materialproducers to design appropriate tasks forlearners. Hence, tasks’ management is acrucial basis for communicative languagesyllabus. Skehen’s model of task complexityTo Skehan (1998), three factors areassociated with task difficulty: codecomplexity (the syntactic and lexicaldifficulty of input), cognitive complexity(the processing demands of the tasks), andcommunicative stress (time pressure and themodality demand). These factors canproduce different demands, and thereforecan influence the quality of learners’performance (Taguchi, 2007).Another factor included in Skehan’s modelis planning time. Previous research hasexplored the effect of planning time on L2output. Planning time would help learners to produce more accurate as well as greaterlevel of lexical complexity. However, incase of accuracy, results could be different.Some studies showed that certain task typesmay lead to more accurate speech whileothers proved that task condition is aninfluential factor which determines thedegree of accuracy. Skehan (1998), asreiterated in Iwashita, McNamara, and Elder(2001), believes that different numbers offactors have impact on task difficulty. Tohim, task dimensions such as abstractnessand familiarity of task information caninfluence the difficulty of the task. Hemaintains that performance conditions (e.g.,concrete vs. abstract information) play acrucial role in determining the level of taskdifficulty. Iwashita, McNamara, and Elder’s taskdimensionsAccording to Iwashita et al. (2001),Skehan’s framework was encouraging;however, some aspects of the frameworkwere questionable such as: (1) the notion ofdifficulty, (2) assessing the candidate’sperformance, (3) inconsistent results, and (4)the complexity of task performance. Iwashita et al. (2001) consider fourdimensions for narrative tasks, with twodifferent performance conditions (+ or -).These task dimensions and performanceconditions are defined as follows:Perspective: When a story is told as if ithappened to the participant, more accuratebut less complex response is produced.However, telling the story from others’viewpoint will make a task more difficultand the result would be different.  Immediacy:If learners have access to thepictures while telling a story, their speechwould be more accurate, but less complex.On the other hand, telling a story withoutpictures in view would be less accurate;hence, narrative tasks considering there-and-