Unique and common effects of decoding and language factors in predicting reading comprehension in grades 1-10

This investigation examined unique and common effects of decoding and language factors that explain variance in reading comprehension in grades 1-10. Participants were 2938 students in 18 schools in two large districts in Florida. The dimensionality of decoding measures (i.e., phonological awareness and decoding fluency) and language measures (i.e., listening comprehension, vocabulary, and syntax) was examined with confirmatory factor analysis and related to a reading comprehension factor comprised of national and state tests. The resulting R2 was compared to the sum of the R2 of decoding-only and language-only models to obtain the unique and common variances explained by language and decoding. Across grades 1-10, most of the variance was explained by either the common variance between the decoding and language factors or the unique effect of the language factor. Results are discussed in the context of an expanded interpretation of the simple view of reading and educational implications are provided.