An Analysis of Text Difficulty across Grades in Korean Middle School English Textbooks Using Coh-Metrix

This study aims to investigate the text difficulty of the reading materials of Korean middle school English textbooks with Coh-Metrix, a software developed by the Institute for Intelligent Systems at the University of Memphis to analyze the linguistic and psycholinguistic features of English text and textbooks with a wide range of indices on cohesion and language.In this study, the textbook corpus consisted of the text files extracted from 13 English textbooks.These files were used for analyzing the text difficulty among grades with Coh-Metrix.The Coh-Metrix indices selected for this study contained basic counts, word frequency, word features, lexical diversity, pronouns, connectives, readability, syntax complexity, syntax similarity, reference cohesion, semantic cohesion, and situation model measures.The results showed that there were significant differences among grades for basic counts, word features, first pronouns, causal and temporal connectives, readability, reference and semantic cohesion, the number of words before main verbs, syntactic similarity, and situation model measures.The differences among grades, however, were not significant for word frequency, lexical diversity, second and third person pronouns, additive connectives, and NP density measures.The findings have educational implications for textbook design and language learning for English learners.