Modeling item-level variance of polysyllabic word reading in developing readers: Exploring semantically related child, word, and child-by-word predictors

•Emphasizes relatively underexplored semantic contributions of word-level features.•Item-level familiarity increased the likelihood that a word was read correctly.•Set for variability, age of acquisition, and morphemes were significant predictors.•The effect of age of acquisition varies across word reading efficiency.•Results support the importance of word knowledge for reading polysyllabic words. Across word reading development, there are important and evolving relationships between oral and written semantic knowledge. Recent research has focused on these relationships, with accumulating evidence supporting the role of word knowledge and related word characteristics as important factors influencing polysyllabic word reading abilities. The purpose of this study was to investigate how semantic-related effects across child-level skills (e.g., general vocabulary knowledge), word-level properties (e.g., age of acquisition), child-by-word-level familiarity (e.g., item-level familiarity), and interactions between key child attributes and word characteristics (e.g., word reading skill by age of acquisition) contribute to polysyllabic word reading. Specifically, we emphasize the semantic contributions of word-level features to word reading development, which have been relatively underexplored in the literature. A sample of elementary school students oversampled for word reading difficulty (N = 92) in Grades 3 to 5 read a set of polysyllabic words (J = 45) and completed a battery of reading and language-related measures. Using cross-classified random-effects models and accounting for various control variables, semantic-related variables representing item-level familiarity; child-level set for variability; and word-level age of acquisition and number of morphemes were significant predictors in the main-effects model. A significant interaction between sight word efficiency and age of acquisition indicated higher probabilities of correctly reading polysyllabic words at lower levels of acquisition for better readers. Results indicate important semantic-related influences on polysyllabic word reading at the child, word, and child-by-word levels, suggesting meaningful relationships between knowledge of the orthographic form of a word and semantic knowledge in developing readers.