Lexical analyses of native and non-native English language instructor speech based on a six-month co-taught classroom video corpus

We developed and analyzed a videotaped corpus of Japanese and English instructors who taught a high school English language class together over a 6-month period. Distributions of lexical items spoken by native and non-native speakers show they are (1) both concentrated within the 2000 most common words found in written language, (2) both skewed towards classroom context, but (3) unequal with regards to interrogative forms (such as what and why) and verbs (such as imperatives used in directing student behavior). These findings respectively suggest that (1) non-native instructors desiring to teach wholly in the target language should focus on common words, (2) students expect classroom context, and (3) native instructors favor content-oriented instruction that demands higher proficiency of students, while non-native instructors prefer step-wise instruction suited for learners across various levels. The last finding in particular may benefit the training of both kinds of instructors.