Braze, D., Kukona, A., Magnuson, J. S., Mencl, W. E., Pugh, K. R., Tabor, W., Van Dyke, J. A., & Shankweiler, D. P. (2009, June 26). Vocabulary makes an independent contribution to reading comprehension in young adults' reading skills. Poster presented at the Sixteenth Annual Meeting of the Society for the Scientific Study of Reading. Boston, MA. [abstract] [PDF]
Purpose: Braze et al. (2007) found decoding together with listening comprehension (Lcomp) account for considerable variance in reading comprehension (Rcomp) among young adults, per the Simple View (Gough & Tunmer, 1986). However, vocabulary made an independent contribution. This new study makes three points. First, earlier conclusions regarding vocabulary generalize to new samples and different stimulus materials. Second, commonality analysis provides a refined picture of the contributions of component skills. Third, we refine our model of lexical representation and access, grounded in the Lexical Quality Hypothesis (LQH, Hart & Perfetti, 2002).
Method: We recruited two cohorts (combined N=135) of young adult poor readers (per Braze etal., 2007). Each cohort was assessed for Rcomp and related abilities (Lcomp, PA, decoding, vocabulary, verbal memory, print experience, IQ). Samples include a wider range of reading skills than would be found in studies of university students. Regression modeling and commonality analysis (CA, Seibold & McPhee, 1979) are used to determine unique and overlapping variances associated with each factor.
Results: Regression models grounded in the Simple View account for substantial, but incomplete portion of non-random variance in Rcomp. As predicted, vocabulary makes an independent contribution to Rcomp, above Lcomp and decoding skill. Moreover, CA supports the specificity of vocabulary in supporting Rcomp.
Conclusions: Details of shared variances of Rcomp predictors, as revealed by CA, have important practical and theoretical significance. These relationships are key to understanding the etiology of poor reading comprehension because efficient comprehension requires that all components of word knowledge become available at the right time for integration. Specificity of vocabulary supports the LQH.