In the late 1980s Batia Laufer worked with teachers who believed that to understand a text it was enough to understand 80% of the text's word tokens. In response, Laufer set out to calculate the minimal text coverage, i.e., percentage of running words in a text the reader should understand to comprehend it reasonably well. In 1992, she explored…

Opportunities for incidental vocabulary acquisition were explored in a 121,000-word corpus of teacher talk addressed to advanced adult learners of English as a second language (ESL) in a communicatively-oriented conversation class. In contrast to previous studies that relied on short excerpts, the corpus contained all of the teacher speech the…