A corpus-based analysis of grammatical complexity as a measure of international teaching assistants’ oral English proficiency

Oral English proficiency is one among several crucial factors to help determine the eligibility of international teaching assistants (ITAs) for various tasks associated with teaching undergraduate students at U.S. universities. The oral English proficiency test (OEPT) is a test used to screen prospective ITAs whose TOEFL speaking scores were below the cutoff required for admission and to determine whether they need additional support courses. Drawing on previous studies conducted in the context of oral assessment and university settings, ten grammatical features were selected to investigate grammatical complexity in the responses of the OEPT test takers. Our study explores which grammatical features are more frequently used by the test takers who passed and failed the test. The results show that the OEPT tasks elicited grammatical features commonly found in academic university registers (e.g., classroom teaching). Highly proficient test takers also used grammatical features commonly found in written texts and more extended spoken discourse (e.g., relative clauses) more frequently than lower proficiency ones. We hope that the findings of this study will inform the ongoing rating scale validation for ITA contexts by providing test developers and raters with specific evidence of grammatical features used by test takers at particular scores.