Understanding Vocabulary: Making Sense of What We Measure, Who We Measure, and How We Measure

Abstract

This dissertation investigates how lexical features relate to vocabulary knowledge in diverse student groups. It consists of three empirical articles that use exploratory factor analysis (EFA) and explanatory item response theory (eIRT) to model the relationship between student proficiency, target word lexical characteristics, different vocabulary assessments, and the interactions between ability and difficulty across dimensions. Paper I identifies five stable latent factors across three word lists: Frequency, Complexity, Proximity, Polysemy, and Diversity. The second and third papers demonstrate the methodological utility of these latent dimensions by modeling target-word characteristics as a predictor in item difficulty. Paper II reports cross-classified interactions between monolingual English speaker reading proficiency scores and lexical dimensions on a synonym task, while Paper III report interactions between the lexical dimensions and English Language Learner classification, while also comparing between synonym and definition tasks. These studies indicate that vocabulary performance varies as a function of student and target word characteristics, and that the relationships interact with one another. In Paper II, monolingual students with low reading comprehension scores were less sensitive to the word frequency advantage and more sensitive to morphologically complex words. In Paper III, English Language Learners with limited proficiency were less sensitive to both the word frequency and morphological complexity. Similarly, students on average found synonym identification tasks less challenging, but limited proficiency ELLs did not show a preference. These findings highlight the importance of considering lexical characteristics and linguistic backgrounds when learning, teaching, and assessing vocabulary. The findings have significant implications for improving vocabulary learning, teaching, and assessment, especially given diverse educational contexts.