XLinguae Journal, Volume 10 Issue 3, June 2017, ISSN 1337-8384 57 The development of complexity, accuracy, and fluency in ESP learners’ writing: A dynamic systems theory Alireza Ahmadi – Hussein Meihami DOI: 10.18355/XL.2017.10.03.05 Abstract There is a paucity of research on the writing complexity, accuracy, and fluency (CAF) of English for specific purposes (ESP) learners. Hence, the purpose of this study was to investigate the development of CAF in the ESP learners’ writing quality while they wrote essays requiring their topical knowledge and the ones requiring their general knowledge. The study benefited from a dynamic systems theory to investigate the development trends of four ESP learners’ writing quality. During the two months, the essays of the ESP learners were examined through different indicators of complexity, accuracy, and fluency. The results revealed that the complexity index of both topical and general essays written by the ESP learners went through the same trends of development. However, this was not the case for the ESP learners’ writing fluency and accuracy. Furthermore, the findings revealed that the ESP learners had higher index of complexity, accuracy, and fluency in topical essays at the beginning of the program and at the end of it when compared with the general essays. Additionally, some variations had been observed among the participants. Key words: topical knowledge, ESP learners, complexity, accuracy, fluency Introduction Second language acquisition (SLA) is not a static process, but a dynamic one. Accordingly, the challenges one may encounter in this process are dynamic; meaning that the practitioners of the field cannot solve the issues through making static decisions. During the recent decades, one of the research ground drawing the attention of SLA researchers (e.g., Lambert & Kormos, 2014; Larsen-Freeman, 2006; Norris & Ortega, 2009; Revesz, Ekiert, & Torgersen, 2014) is how to examine the emergence of these challenges in terms of complexity, accuracy, and fluency (hereafter CAF). In the word of Thelen and Smith (1994), the conduction of such research is due to the desire of the SLA researchers to find the direction of “motor change” and its role in intensifying the complexity of the challenges. The SLA researchers use the assumptions they receive from the linguists and from the “first and early language acquisition research” (Larsen-Freeman, 2006; p. 590) to formulate the theoretical underpinnings of CAF which are Emergentism and dynamic systems theory (Spoelman & Verspoor, 2010). As an approach to cognition, emergentism follows the principles which highlight the role of interaction between environment and individuals. To touch the issue in SLA, Ellis (1998) believes that the complexity of language is due to having a massive and a complex environment which the development processes are exposed to. It is a metaphorical trick to use emergentism since the development process of language learning is an ever-lasting one. From that perspective, we may establish a relationship between emergentism approach and usage-based language learning (Spoelman & Verspoor, 2010) in which the external factors such as the frequency of language development factors are crucial in the complexity of the language learning. Owing to this, Tomasello (2003) posits that the type and the token frequency of language structures specify the language structure emergent.