Unknown Vocabulary Density and Reading Comprehension: Replicating Hu and Nation (2000)

Hu and Nation's (2000) study, which stipulated that second language (L2) readers need to be familiar with 98% of lexical items for adequate text comprehension, has become highly influential in L2 vocabulary research and pedagogy. However, the 98% critical threshold figure is based on findings from a research project in which a regression analysis was conducted with only 66 university students in New Zealand. The present study replicated Hu and Nation's research in a context different from a typical Western, educated, industrialized, rich, and democratic context with a sample of 104 Sri Lankan adult L2 learners in a nonacademic context. They each took a Vocabulary Levels Test and read one of five versions of two reading texts at different levels of density of unknown words before answering comprehension questions. The results of the original study could not be fully replicated. A one-page Accessible Summary of this article in nontechnical language is freely available in the Supporting Information online and at