Student talk as a source for incidental vocabulary learning: what can corpora tell us?

While experimental studies have confirmed the value of student talk for incidental L2 vocabulary learning, no studies have evaluated it from the corpus linguistics perspective. Taking the Vietnamese EFL university context as a case, this study used corpus linguistics to investigate the value of student talk for incidental vocabulary learning. Three corpora were created: a cross-sectional corpus of 381 student-student interactions in tertiary English language courses, and two longitudinal corpora derived from all lessons in each course. The analyses of words, represented by Nation’s (2012) BNC/COCA lists, and core formulaic sequences, represented by Martínez and Schmitt’s (2012) Phrasal Expressions List, were respectively undertaken with RANGE and Sketch Engine. Results show that knowledge of the most frequent 1000-word families is needed for reasonable comprehension of student talk. 5.23%−23% of the high-frequency word families and 0.59%−13.47% of the core formulaic sequences were encountered multiple times during each course. The results suggest student talk is an excellent source for learning and reinforcing high-frequency vocabulary and a good source for learning and reinforcing core formulaic sequences. Our study highlights the value of student talk as an input source for low-proficiency learners to learn vocabulary incidentally and showcases how corpus linguistics can inform L2 pedagogy.