Making sense of learner performance on tests of productive vocabulary knowledge

This paper offers a solution to a significant problem for teachers and researchers of language learning that confounds their interpretations and expectations of test data: the apparent simplicity of tests of vocabulary knowledge masks the complexity of the constructs they claim to measure. We first scrutinise task elements in two widely cited productive vocabulary measures, Lex30 (Meara and Fitzpatrick, 2000) and the Lexical Frequency Profile (LFP, Laufer and Nation, 1995), in order to gain a more precise understanding of the relationship between test performance and learner knowledge. Next, in three empirical studies (N = 80, 80, 100) we compare L2 learners’ performance on Lex30, as the static point of reference, with LFP and with two new tests designed to investigate specific elements of the vocabulary test tasks. Correlation analyses indicate systematic differences in the tests’ capacity to capture information about the quality of learners’ word knowledge and the size of their vocabulary resource. Using the findings from this empirical work, we formulate a model of vocabulary ‘capture’ onto which test tasks can be mapped. We demonstrate how capturing key elements of the relationship between test scores and lexical competence can guide teachers and researchers in applying and interpreting vocabulary tests.