A Method to Measure the Reading Difficulty of Japanese Words

In this paper, we propose an automatic method to measure the reading difficulty of Japanese words. The proposed method uses a statistical transliteration framework, which was inspired by statistical machine translation research. A Dirichlet process model is used for the alignment between single kanji characters and one or more hiragana characters. The joint probability of kanji and hiragana is used to measure the difficulty. In our experiment, we carried out a linear discriminate analysis using three kinds of lexicons: a Japanese place name lexicon, a Japanese last name lexicon and a general noun lexicon. We compared the discrimination ratio given by the proposed method and the conventional method, which estimates a word difficulty based on manually defined kanji difficulty. According to the experimental results, the proposed method performs well for scoring Japanese proper noun reading difficulty. The proposed method produces a higher discrimination ratio with the proper noun lexicons (14 points higher on the place name lexicon and 26.5 points higher on the last name lexicon) than the conventional method.