Lexical and Syntactic Complexity across Adjacent IELTS Writing Task 2 Band Levels: A Corpus-Based Study
Authors
- Truong Van Uyen Independent researcher
Abstract
Lexical and syntactic complexity are important indicators of second language writing proficiency, particularly in assessment-oriented contexts such as IELTS Writing Task 2. However, limited attention has examined whether selected complexity measures can distinguish closely related IELTS band levels. A small-scale learner corpus of 30 essays, with 10 essays per band level, was analyzed quantitatively. Lexical diversity was measured using the Measure of Textual Lexical Diversity (MTLD), lexical sophistication was operationalized as the percentage of Academic Word List (AWL) items, and syntactic complexity was assessed through mean sentence length (MSL). One-way ANOVA showed a significant difference in lexical diversity, whereas AWL percentage and MSL showed non-significant upward trends. Post-hoc comparisons indicated that the significant MTLD difference occurred between Bands 6 and 8 rather than between immediately adjacent bands. Because the corpus consists of band-labeled instructional essays, the findings should be interpreted as exploratory rather than generalizable evidence of IELTS band distinctions.
References
Aljburi, M. A., & Khaghaninejad, M. S. (2024). Exploring the efficiency of associative vocabulary teaching strategies to foreign language learners. International Journal of Instruction, 17(3), 291–314. https://doi.org/10.29333/iji.2024.17316a
Ayadi, M. (2023). Lexical richness and syntactic complexity as predictors of academic writing performance. Journal of English Studies in Arabia Felix, 2(1), 23–33. https://doi.org/10.56540/jesaf.v2i1.43
Bachman, L. F. (1990). Fundamental considerations in language testing. Oxford University Press.
Biber, D., Gray, B., & Staples, S. (2016). Predicting patterns of grammatical complexity across language exam task types and proficiency levels. Applied Linguistics, 37(5), 639–668. https://doi.org/10.1093/applin/amu059
Boers, F., Dang, T. C. T., & Strong, B. (2017). Comparing the effectiveness of phrase-focused exercises: A partial replication of Boers, Demecheleer, Coxhead, and Webb (2014). Language Teaching Research, 21(3), 362–380. https://doi.org/10.1177/1362168816651464
Bulté, B., & Housen, A. (2012). Defining and operationalising L2 complexity. In A. Housen, F. Kuiken, & I. Vedder (Eds.), Dimensions of L2 performance and proficiency: Complexity, accuracy and fluency in SLA (pp. 21–46). John Benjamins. https://doi.org/10.1075/lllt.32.02bul
Canale, M. (1983). From communicative competence to communicative language pedagogy. In J. C. Richards & R. W. Schmidt (Eds.), Language and communication (pp. 2–27). Longman.
Canale, M., & Swain, M. (1980). Theoretical bases of communicative approaches to second language teaching and testing. Applied Linguistics, 1(1), 1–47. https://doi.org/10.1093/applin/I.1.1
Coxhead, A. (2000). A new academic word list. TESOL Quarterly, 34(2), 213–238. https://doi.org/10.2307/3587951
Crossley, S. A., & McNamara, D. S. (2012). Detecting the first language of second language writers using automated indices of cohesion, lexical sophistication, syntactic complexity and conceptual knowledge. In S. Jarvis & S. A. Crossley (Eds.), Approaching language transfer through text classification (pp. 106–126). Multilingual Matters. https://doi.org/10.21832/9781847696991-005
Dinh, T. N. (2025). Complexity, fluency, and accuracy in written works of Vietnamese learners of English: A replication study. International Journal of TESOL & Education, 5(2), 29–56. https://doi.org/10.54855/ijte.25522
Do, N. H. M., & Le, Q. T. (2023). Lexical collocation errors in essay writing: A study into Vietnamese EFL students and their perceptions. International Journal of Language Instruction, 2(2), 1–20. https://doi.org/10.54855/ijli.23221
Du, M., Lu, M., Dai, Y., & Wang, F. (2025). A corpus-based analysis of verb collocations in human and AI-generated IELTS writing. Journal of Educational Technology and Innovation, 7(2), 67–80. https://doi.org/10.61414/mzmmrq74
Ellis, R. (2003). Task-based language learning and teaching. Oxford University Press.
Estaji, M., & Hashemi, M. (2022). Phraseological competence in IELTS academic writing task 2: Phraseological units and test-takers’ perceptions and use. Language Testing in Asia, 12, Article 34. https://doi.org/10.1186/s40468-022-00180-7
Hawkey, R. (2006). Impact theory and practice: Studies of the IELTS test and Progetto Lingue 2000. Cambridge University Press.
Ho, T. L. U. (2024). Problems with academic writing encountered by EFL postgraduate students at a university in the Mekong Delta. International Journal of Language Instruction, 3(1), 1–16. https://doi.org/10.54855/ijli.24311
Housen, A., Kuiken, F., & Vedder, I. (Eds.). (2012). Dimensions of L2 performance and proficiency: Complexity, accuracy and fluency in SLA. John Benjamins. https://doi.org/10.1075/lllt.32
Huong, P. T. T., & Phúc, T. H. (2023). Lexical features and the quality of Vietnamese EFL students’ online English writings. Journal of University Teaching & Learning Practice, 20(2). https://doi.org/10.53761/1.20.02.06
Hyland, K. (2003). Second language writing. Cambridge University Press.
IELTS. (2023). IELTS writing band descriptors. https://ielts.org/cdn/Guides/ielts-writing-band-descriptors.pdf
Ilyas, D., Mimenbayeva, A., & Kadirbayeva, A. (2025). Neural network with fine-tuned BERT for IELTS writing evaluation. In Proceedings of the 2025 International Conference on System Integration and Smart Technologies (pp. 234–241). IEEE. https://doi.org/10.1109/sist61657.2025.11139356
Imaz Agirre, A., Arias-Hermoso, R., & Ipiña, N. (2025). The effect of an intervention focused on academic language on CAF measures in the multilingual writing of secondary students. International Review of Applied Linguistics in Language Teaching, 63(2), 1373–1396. https://doi.org/10.1515/iral-2023-0137
Jarvis, S. (2013). Capturing the diversity in lexical diversity. Language Learning, 63(s1), 87–106. https://doi.org/10.1111/j.1467-9922.2012.00739.x
Khudaverdiyeva, T. (2025). The importance of writing in language acquisition: A cognitive, communicative and pedagogical perspective. Global Spectrum of Research and Humanities, 2(3), 127–138. https://doi.org/10.69760/gsrh.0203025014
Khushik, G. A., & Huhta, A. (2020). Investigating syntactic complexity in EFL learners' writing across Common European Framework of Reference levels A1, A2, and B1. Applied Linguistics, 41(4), 506–532. https://doi.org/10.1093/applin/amy064
Kim, M., Kim, Y. J., & Kang, S. (2025). The dynamics of changes in linguistic complexity and writing scores in timed argumentative writing among beginning-level EFL learners. International Review of Applied Linguistics in Language Teaching, 63(4), 2891–2925. https://doi.org/10.1515/iral-2023-0287
Kyle, K., & Crossley, S. A. (2015). Automatically assessing lexical sophistication: Indices, tools, findings, and application. TESOL Quarterly, 49(4), 757–786. https://doi.org/10.1002/tesq.194
Kyle, K., & Crossley, S. A. (2018). Measuring syntactic complexity in L2 writing using fine-grained clausal and phrasal indices. The Modern Language Journal, 102(2), 333–349. https://doi.org/10.1111/modl.12468
Lahuerta Martínez, A. C. (2024). The role of syntactic and lexical complexity in undergraduate writing quality. Ibérica, 47, 251–274. https://doi.org/10.17398/2340-2784.47.251
Larsen-Freeman, D. (2019). On language learner agency: A complex dynamic systems theory perspective. The Modern Language Journal, 103(S1), 61–79. https://doi.org/10.1111/modl.12536
Laufer, B., & Nation, P. (1995). Vocabulary size and use: Lexical richness in L2 written production. Applied Linguistics, 16(3), 307–322. https://doi.org/10.1093/applin/16.3.307
Le, D. M. T., & Pham, T. S. (2026). Lecturers’ perceptions of Google Docs for e-portfolios to improve students’ IELTS writing. International Journal of Language Instruction, 5(1), 18–44. https://doi.org/10.54855/ijli.26512
McCarthy, P. M., & Jarvis, S. (2007). vocd: A theoretical and empirical evaluation. Language Testing, 24(4), 459–488. https://doi.org/10.1177/0265532207080767
McCarthy, P. M., & Jarvis, S. (2010). MTLD, vocd-D, and HD-D: A validation study of sophisticated approaches to lexical diversity assessment. Behavior Research Methods, 42(2), 381–392. https://doi.org/10.3758/BRM.42.2.381
Nguyen, H. N., & Nguyen, D. K. (2022). Vietnamese learners’ performance in the IELTS Writing Task 2: Problems, causes, and suggestions. International Journal of TESOL & Education, 2(1), 170–189. https://doi.org/10.54855/ijte.222111
Nguyen, H. V., Nguyen, M. X. N. C., & Dao, P. (2020). The impact of IELTS on English language teachers in Central Vietnam (IELTS Research Reports Online Series No. 1). British Council, Cambridge Assessment English, and IDP: IELTS Australia. https://www.ielts.org/teaching-and-research/research-reports
O'Leary, M., & Steinkrauss, R. (2022). Syntactic and lexical complexity in L2 English academic writing: Development and competition. Ampersand, 9, Article 100096. https://doi.org/10.1016/j.amper.2022.100096
Ortega, L. (2003). Syntactic complexity measures and their relationship to L2 proficiency: A research synthesis of college-level L2 writing. Applied Linguistics, 24(4), 492–518. https://doi.org/10.1093/applin/24.4.492
Ortega, L. (2012). Epilogue: Exploring L2 writing–SLA interfaces. Journal of Second Language Writing, 21(4), 404–415. https://doi.org/10.1016/j.jslw.2012.09.002
Panagopoulos, P., Andria, M., Mikros, G., & Varlokosta, S. (2024). Writing in L2 Greek: Exploring the effect of L2 proficiency and learning context on complexity, accuracy, and fluency. Journal of Second Language Writing, 64, Article 101111. https://doi.org/10.1016/j.jslw.2024.101111
Pham, Q. N., & Pham, V. P. H. (2024). Common syntactic errors in the writing skills of the 3rd year students at Van Lang University. International Journal of TESOL & Education, 4(2), 118–144. https://doi.org/10.54855/ijte.24427
Phuoc, N. N., & Barrot, J. S. (2022). Complexity, accuracy, and fluency in L2 writing across proficiency levels: A matter of L1 background? Assessing Writing, 54, Article 100673. https://doi.org/10.1016/j.asw.2022.100673
Polat, N., Mahalingappa, L., & Mancilla, R. (2024). IELTS and written syntactic complexity as predictors of GPA of multilingual international graduate students. AERA Open, 10, 1–16. https://doi.org/10.1177/23328584241258729
Read, J. (2000). Assessing vocabulary. Cambridge University Press.
Suzuki, S., & Kormos, J. (2020). Linguistic dimensions of comprehensibility and perceived fluency: An investigation of complexity, accuracy, and fluency in second language argumentative speech. Studies in Second Language Acquisition, 42(1), 143–167. https://doi.org/10.1017/S0272263119000421
Tran, T. D. (2015). An exploratory study of current assessment practices for improving the learning of English as a foreign language (EFL) in two Vietnamese universities [Doctoral dissertation, Queensland University of Technology]. https://eprints.qut.edu.au/84622/
Truong, T. V. (2024). Analyzing lexical characteristics in IELTS Writing Task 2 essays: A study of Vietnamese students from non-English majors. International Journal of Research Publication and Reviews, 5(12), 3233–3245. https://doi.org/10.55248/gengpi.5.1224.250102
Wang, Y. (2023). The interplay of linguistic complexity measures and their relation to the quality of L2 argumentative writing. Communications in Humanities Research, 11, 31–39. https://doi.org/10.54254/2753-7064/11/20231365
Wolfe-Quintero, K., Inagaki, S., & Kim, H.-Y. (1998). Second language development in writing: Measures of fluency, accuracy, and complexity. University of Hawai‘i Press.
Wu, J. (2025). Comparing linguistic features between human-written high-scoring IELTS essays and AI-generated ones. Journal of Humanities and Social Sciences Studies, 7(8), 68–77. https://doi.org/10.32996/jhsss.2025.7.8.8
Yang, Y., Yap, N. T., & Ali, A. M. (2023). Predicting EFL expository writing quality with measures of lexical richness. Assessing Writing, 57, Article 100762. https://doi.org/10.1016/j.asw.2023.100762
Zhang, S., Zhang, H., & Zhang, C. (2022). A dynamic systems study on complexity, accuracy, and fluency in English writing development by Chinese university students. Frontiers in Psychology, 13, Article 787710. https://doi.org/10.3389/fpsyg.2022.787710
Downloads
This work is licensed under a Creative Commons Attribution 4.0 International License.
The copyright of all articles published in the International Journal of TESOL & Education (ijte) remains with the Authors, i.e. Authors retain full ownership of their article. Permitted third-party reuse of the open access articles is defined by the applicable Creative Commons (CC) end-user license which is accepted by the Authors upon submission of their paper. All articles in the ijte are published under the CC BY-NC 4.0 license, meaning that end users can freely share an article (i.e. copy and redistribute the material in any medium or format) and adapt it (i.e. remix, transform and build upon the material) on the condition that proper attribution is given (i.e. appropriate credit, a link to the applicable license and an indication if any changes were made; all in such a way that does not suggest that the licensor endorses the user or the use) and the material is only used for non-commercial purposes.
Authors retain copyright and grant the journal the right of first publication with the work simultaneously licensed under a Creative Commons Attribution 4.0 International License that allows others to share the work with an acknowledgment of the work's authorship and initial publication in this journal.
Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository, in a journal or publish it in a book), with an acknowledgment of its initial publication in this journal.
