Vocabulary Usage and Intelligibility in Learner Language

In verbal communication, the primary purpose of which is to convey and understand messages, speakers need to make intelligible utterances. The intelligibility of an utterance depends on the sentence structure, discourse, and the vocabulary usage. In foreign-language utterances, “errors” can reduce the intelligibility. The correct and appropriate use of vocabulary is essential for successful message conveyance especially in foreign language communication where people often have difficulty in constructing sentences precisely, and where they rely more on vocabulary because of their lower grammatical competence. Vocabulary skill development has become one of the high-priority issues in recent foreign language education. We analysed on the correlation between vocabulary usage and the intelligibility of utterances made by Japanese learners of English by investigating to what extent lexical errors interfere with the intelligibility of utterances. We did this based on the error-coded learner corpus in which each sentence is labelled with its levels of intelligibility. More precisely, we calculated lexical semantic relatedness between an erroneous word and a correct word, and then observed how the relatedness values are distributed across different levels of intelligibility and different proficiency levels as well. The remainder of this paper is as follows. In Section 2, we discuss how intelligibility is positioned in foreign language learning and teaching. Section 3 explains the corpus data used in the experiment, focusing especially on data annotation of intelligibility as evaluated by humans and the analysis of the relationship between intelligibility and learner errors. Section 4 describes our further investigation into the correlation between lexical errors and intelligibility conducted by focusing on lexical semantic relatedness between an erroneous word and a correct word. In Section 5, we draw some general conclusions.