Inter-individual Variability in CAF: A Case Study of Two Individuals and Two Pairs’ Written Productions [PP: 61-74] Mahboobeh Saadat Sahar Zahed Alavi (Corresponding author) Department of Foreign Languages and Linguistics Shiraz University, Iran ABSTRACT The present study tracked the development of general measures of complexity, accuracy and fluency (CAF), and specific measures of accuracy and complexity in the writings of two EFL learners writing individually, and those of two pairs of EFL learners writing in pairs within the framework of dynamic systems theory. The individuals and the pairs were similarly asked to do 7 tasks during a semester. The learners’ developmental pathways as well as the differences between individuals and pairs in terms of general and specific measures of CAF across the 7 tasks were depicted through graphs. Results indicated that the performance of learners in each of the measures was non-linear during the semester. Moreover, concerning general measures of CAF, learners writing individually outperformed in terms of fluency and complexity features. However, no clear distinction emerged in terms of general accuracy measures of their writings. Furthermore, development of general and specific accuracy measures in the writings was consistent. However, although it was found that the learners writing individually outperformed in terms of general measure of complexity, this developmental pattern was not evident in their performance in terms of specific complexity measures. Keywords: Accuracy, Fluency, Complexity, Development, Dynamic Systems Theory ARTICLE INFO The paper received on Reviewed on Accepted after revisions on 25/03/2017 15/04/2017 09/06/2017 Suggested citation: Saadat, M. & Alavi, S. (2017). Inter-individual Variability in CAF: A Case Study of Two Individuals and Two Pairs’ Written Productions. International Journal of English Language & Translation Studies. 5(2), 61-74. 1. Introduction Learners’ language proficiency in writing can effectively be evaluated through three measures of complexity, accuracy, and fluency (CAF) (Abrams & Rott, 2016; Biber, Gray & Staples, 2014; Bulté & Housen, 2012; Housen & Kuiken, 2009; Housen, Kuiken & Vedder, 2012; Révész, 2011; Shehadeh, 2011; Spoelman & Verspoor, 2010; Thai & Boers, 2016; Trebits, 2014). Complexity is pertinent to the restructuring of the performance. However, accuracy deals with controlling one’s production and avoiding errors. Fluency is related to one’s ability both to connect words to their meanings, and to attend to what one is presenting (Ellis, 2008). Despite the fact that CAF measures are used to assess learners’ proficiency, indicating the multi-componential nature of language use and development, dynamic systems theory explicates developmental differences within an individual as well as across groups. In other words, there is variation due to both intra-individual and inter-individual differences. Therefore, the theory advocates that learning a second language is an individualized nonlinear endeavor (Larsen-Freeman & Cameron, 2008). Although much of language performance is conducted individually, collaborative language performance combines individuals’ problem-solving with social orientation. Indeed, collaborative performance helps individuals pay attention to their choice of syntax, semantics and discourse in collaboration with each other (Wigglesworth & Storch, 2012). Pedagogically speaking, collaborative language production can facilitate learners’ performance by providing them with more time and