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This systematic review examined whether building content knowledge in science and/or social studies topics during English Language Arts (ELA) instruction enhances vocabulary and comprehension. It also described how ELA instruction has been leveraged to build content knowledge in the elementary years. A systematic search of the extant literature identified eight (quasi)experimental studies. Five of the eight studies met standards of research quality for validating causal inferences. The results of the meta-analysis of the five studies showed that supporting content knowledge in ELA strengthened vocabulary related to content being taught (effect size g = 0.29). The average effect size for comprehension was positive and significant when standardized comprehension measures and researcher-developed comprehension measures were considered together (g = 0.24). In addition, we found common and different patterns of content-rich ELA instruction regarding the use of texts, reading, writing, discussion, and/or hands-on activities.

This study synthesized impacts of integrated literacy and content-area instruction (i.e., science, social studies) on vocabulary and comprehension outcomes in the elementary years (i.e., kindergarten through fifth grade). A systematic search of the extant literature identified 35 (quasi)experimental studies. Random-effects models were used to combine effect sizes across studies. Results of meta-analysis revealed that the overall effects were positive and significant for vocabulary (effect size [ES] = 0.91) and comprehension (ES = 0.40). Moreover, a significant positive effect was observed for standardized comprehension outcomes (ES = 0.25), but not for standardized vocabulary outcomes. Supplementary analysis including studies with content knowledge outcomes demonstrated the positive and significant overall effect for content knowledge (ES = 0.89). In addition, no significant moderators of the effect sizes were found among features of research design and characteristics of interventions, perhaps partly due to the small number of studies. The results of our meta-analysis indicate that integrated literacy and content-area instruction has potential to enhance vocabulary words taught to students and comprehension in the elementary years, with the additional benefit of simultaneously cultivating science and social studies knowledge.

Despite the importance of identifying individuals with reading disabilities, existing operational definitions of reading disability do not result in reliable identification. A large part of the problem arises from measurement error when a cut-point is imposed on a continuous distribution, especially for low base-rate conditions. One way to reduce measurement error is to include additional predictors in reading disability models. The present study examined co-occurring math disability as a possible additional criterion for predicting reading disability. Meta-analysis was used to examine the probability of individuals with reading disability also having a comorbid math disability. The main result was an average weighted odds ratio of 2.12, 95% confidence interval [1.76, 2.55], indicating that students with a math disability are just over 2 times more likely to also have a reading disability than those without a math disability. The purpose of the present study was to use meta-analysis to examine the extent to which the presence of math disability was associated with greater risk of reading disability.

How prevalent is dyslexia? A definitive answer to this question has been elusive because of the continuous distribution of reading performance and predictors of dyslexia and because of the heterogeneous nature of samples of poor readers. Samples of poor readers are a mixture of individuals whose reading is consistent with or expected based on their performance in other academic areas and in language, and individuals with dyslexia whose reading is not consistent with or expected based on their other performances. In the present article, we replicate and extend a new approach for determining the prevalence of dyslexia. Using model-based meta-analysis and simulation, three main results were found. First, the prevalence of dyslexia is better represented as a distribution that varies as a function of severity as opposed to any single-point estimate. Second, samples of poor readers will contain more expected poor readers than unexpected or dyslexic readers. Third, individuals with dyslexia can be found across the reading spectrum as opposed to only at the lower tail of reading performance. These results have implications for screening and identification, and for recruiting participants for scientific studies of dyslexia.

Despite decades of research, it has been difficult to achieve consensus on a definition of common learning disabilities such as dyslexia. This lack of consensus represents a fundamental problem for the field. Our approach to addressing this issue is to use model-based meta-analyses and Bayesian models with informative priors to combine the results of a large number of studies for the purpose of yielding a more stable and well-supported conceptualization of reading disability. A prerequisite to implementing these models is establishing informative priors for dyslexia. We illustrate a new approach for doing so based on the known distribution of the difference between correlated variables, and use this distribution to determine the proportion of poor readers whose poor reading is unexpected (i.e., likely to be due to dyslexia) as opposed to expected.

This study examined the effects of reading modality (oral vs. silent) on comprehension in elementary school students with a specific learning disability in reading (N = 77). A 2 (development-level) × 2 (reading modality) × 2 (time) mixed factorial analysis of variance (ANOVA) was conducted to determine the influence of these variables on comprehension. Significant main effects were found for reading modality and time on comprehension, but the main effect for developmental level was not significant. Students understood more of what was read orally than silently and showed improved comprehension across the year. The development-level by modality interaction was significant. Early elementary students benefited from oral reading in terms of comprehension, whereas equivalent comprehension was observed for late elementary students across modalities. No other two- or three-way interactions were significant. Results from this study suggest that reading modality is an important variable to consider for researchers and educators who are interested in the construct of reading comprehension.