Discourse Modeling of Non-Native Spontaneous Speech Using the Rhetorical Structure Theory Framework

This study aims to model the discourse structure of spontaneous spoken responses within the context of an assessment of English speaking proficiency for non-native speakers. Rhetorical Structure Theory (RST) has been commonly used in the analysis of discourse organization of written texts; however, limited research has been conducted to date on RST annotation and parsing of spoken language, in particular, non-native spontaneous speech. Due to the fact that the measurement of discourse coherence is typically a key metric in human scoring rubrics for assessments of spoken language, we initiated a research to first obtain RST annotations on non-native spoken responses from a standardized assessment of academic English proficiency. Afterwards, based on the annotations obtained, automatic parsers were built to process non-native spontaneous speech. Finally, a set of effective features were extracted from both manually annotated and automatically generated RST trees to evaluate the discourse structure of non-native spontaneous speech, and then employed to further improve the validity of an automated speech scoring system.