The use of tasks, as an effective tool to improve quality of foreign language teaching, has significantly grown in recent years (Ellis, 2003; Nunan, 1991, 2004; Skehan, 1996, 2003). A variety of definitions have been given for pedagogical tasks (for example Bygate, Skehan, & Swain, 2001; Ellis, 2003; Skehan, 1998). Nunan (2004, p. 4) defines pedagogical task as “a piece of classroom work which involves learners in comprehending, manipulating, producing or interacting in the target language while their attention is principally focused on mobilizing their grammatical knowledge in order to express meaning, and in which the intention is to convey meaning rather than to manipulate form”.

     According to Ellis’ (2003) definition, task is “a workplan that requires learners to process language pragmatically in order to achieve an outcome that can be evaluated in terms of whether the correct or appropriate propositional content has been conveyed”. Although there have been a lot of disagreements among researchers about the efficiency of tasks (DeKeyser, 1998; Doughty, 1991; Lightbown, 1998; Lightbown & Spada, 1990; Norris & Ortega, 2001; Pawlak, 2006; Robinson, 1996; Spada & Lightbown, 1993; Swain, 1985 ), they have remained a major part of language teaching profession across the world.

      Nunan (1991) says that communicative tasks help bridge the gap between language learning in an educational setting and authentic language use in the real world; therefore, they are believed to contribute incidentally to fluency and accuracy of language use (Ellis, 1997). Hyland (2002) believes that there are generic skills and forms of language that are shared by a range of disciplines, professions, or purposes, and that ESP involves teaching general skills and forms that can be transferred across contexts and purposes.

     This study aimed to investigate how tasks can be employed to improve writing ability of language learners in ESP courses. To achieve this objective, two types of tasks were employed in two separate ESP courses. Two groups of undergraduate student of Economics were selected for this study. Throughout these courses, the first group of language learners was given a number of one-way tasks and the second group was taught by two-way tasks. The writing proficiency of learners was examined by a pretest and a posttest.

2. Literature review

Among various task categorizations, one of them divides tasks into one-way and two-way tasks. Two-way tasks allow for interaction among participants and share of responsibility to get involved in a learning activity in order to achieve a goal. There is a variety of two-way tasks such as jigsaw and text reconstruction. Ellis (2003), Izumi and Izumi (2004), and Mackey (2012) pointed out that two-way tasks allow participants to share information with the aim of fulfilling a goal. In the one-way task approach, no interaction takes place between or among learners in a learning environment to complete a task or achieve a goal (Ellis, 2003; Izumi & Izumi, 2004; Mackey, 2012). In other words, there is no share of responsibility between two individuals or among learners as a collective work plan to complete a task. When a one-way task is performed, information is held by a single person and there is no chance for negotiation or interaction between students. According to Mackey (2012), one-way tasks involve no transfer of information or interaction, and learner individually takes the burden of completing the task. Examples of one-way tasks include listen-and-do tasks, fill-in-blanks exercises, translation, and telling a personal story. According to Iwashita (2001), one-way tasks offer a higher chance of producing more modified output than two-way tasks.

     According to Krahnke (1987, p.61) task-based instruction is appropriate in ESP because learners “have a clear and immediate need to use language for a well-defined purpose.” Long and Porter (1985) and Long (1989) suggest that group work and task can produce a higher quality of talk among language learners. Grosse (1988) states that small-group work for the ESP classroom can improve the quality of learning among language learners and address the affective needs of the learners, resulting in an increased level of motivation among them.

    The role that is given to each learner in one-way and two-way tasks might have some impact on the effectiveness of the tasks. Yule and McDonald (1990) experimented with adult mixed ability pairs in one-way tasks and found if the weaker learner is placed in the sender’s position, the task promoted far richer interaction than if the stronger learner was the sender. Therefore, the assignment of roles in task-based language teaching must be done carefully.

     Having given two types of tasks (one-way and two-way) to two groups of undergraduate students of Economics, researchers of this study tried to examine the effectiveness of these tasks in teaching writing skills to ESP students. Proficiency levels of the groups in general English was tested by a sample of Michigan TOEFL test. Also, a pretest and a posttest of writing were administered before and after the treatment period in order to compare the two groups with each other. In this way, the study tried to answer the following question:

Is there any difference between the effectiveness of one-way and two-way tasks for teaching writing skills to L2 learners in ESP courses?  

3. Methodology

3.1 Participants

Participants of the study were 32 undergraduate students of Economics at Chabahar Maritime University. All of them were at low-intermediate level general English proficiency. A sample of Michigan TOEFL test was used to select these participants from a larger group of undergraduate students. All of them were Persian native speakers. They were between 19 and 23 years old, including 19 males and 13 females.

3.2 Materials

In addition to a sample of Michigan TOEFL test, a pretest and a posttest was used to examine writing ability of the participants. Each test included three topics. Participants were expected to write a paragraph about each topic in Economics. The aim of these tests was to examine grammatical ability of participants and their ability to communicate about a special subject in Economics. These tests were scored by researchers of the study and professor in Economics.

3.3 Procedure

Participants of the study were selected from a larger group of 71 undergraduate students of Economics. After the selection of 32 participants for the main part of the study, they were given a pretest. In this test, they were expected to write three paragraphs about three subjects in Economics. Then, participants were divided into two groups, each one consisting of 16 participants. These two groups attended two separate courses of 15 sessions. Throughout the treatment period, participants of the first group were given a number of one-way tasks in writing. In these tasks, participants were expected to write a paragraph about special subjects in Economics. In each task, one of the participants was given some information about a topic. This participant had to transfer this information to his/her partner. Then, the partner had to write a paragraph about that subject. Therefore, one participant of each pair was responsible for providing information and the other participant was responsible for writing. After the treatment period, participants took the posttest. Pretest and posttest were scored by researchers of the study and a university professor in Economics.

3.4 Data analysis

Two paired t-tests were used to compare the scores of each group in pretest and posttest. The aim was to find whether the groups had a significant improvement throughout the course. Also, two unpaired t-tests were used to compare scores of the groups. The aim of the first unpaired t-test was compare scores of the two groups in the pre-test, and the second one was used to compare the scores of the two groups in the posttest. Results obtained by these two tests could reveal any significant difference between the performances of the two groups.