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Learning Disabilities, Vocabulary, and Reading Comprehension


By: Daniel J. Dunleavy

The ability to read is an essential skill that can greatly impact educational and professional success. Reading ability, however, is not one distinct phenomenon. It can be broken down into several smaller, related skills. This includes, but is not limited to, word recognition, connection of a written word to its verbal equivalent, and the comprehension of written materials. How these skills relate to one another and impact overall reading comprehension is of great interest to schools, teachers, and educational researchers. A deficit in any one skill could serve as an important marker for continued deficits in overall reading ability as the child ages. In this case, early identification of such deficits could be used by educators to help get students extra help and resources, before their educational success is impacted.

More formally, we can ask whether there is a relationship between vocabulary knowledge and reading comprehension. In other words, does one help predict the other? Do they support and reinforce one another? Or do they both grow together, as children progress through school? What about children with learning disabilities? Are there differences in these skills among these children, compared to their classmates without learning disabilities?

A study recently published in the Journal of Educational Psychology sought to explore these types of questions. A team of psychologists, led by Dr. Jamie Quinn, a researcher at the Florida Center for Reading Research, analyzed data from nearly 15,000 students. Data was collected from 440 lower-performing schools in Florida during the 2002-2003 school year, while the students were in kindergarten, through the 2007-2008 school year, when they were in the fourth grade. A portion of these students were identified by their school systems as having a learning disability. Tests of vocabulary knowledge and reading comprehension were given to students in the Spring of each school year.

The authors of the current study were able to use these test scores to see how student vocabulary and reading comprehension changed over time and how each of these skills influenced the other. In other words, they created a statistical model that revealed how scores on a vocabulary test, for instance, changed as the child aged, and how change in those vocabulary test scores might have impacted their performance on reading comprehension tests. The authors also attempted to take into account other factors, such as how enrollment in a particular school might impact their test performance.

Returning to our original questions, the study yielded several key findings. First, the authors identified a bidirectional influence between vocabulary knowledge and reading comprehension. Strong vocabulary skills seem to lead to strong growth in reading comprehension skills. Similarly, strong reading comprehension skills seem to lead to strong growth in vocabulary knowledge. The same claims could be said to be true, though to a lesser extent, of children with poor vocabulary and reading comprehension skills. These findings, however, were only shown to be present among children without a learning disability.

Second, students with a learning disability started out with lower scores on vocabulary and comprehension tests. In this study, despite having an initial deficit, these students showed greater growth between the kindergarten and fourth grade, than those without a learning disability. Though an important finding, these students still scored lower on each set of tests, on average, than those without a learning disability. This highlights the need for continued support and development of more effective educational interventions for students with learning disabilities. While greater growth between kindergarten and fourth grade is to be welcomed, the findings show that there is still work to be done to help these students succeed.

The study by Dr. Quinn and colleagues is a welcome advance of our understanding of student reading comprehension and factors that impact it. Future research will need to explore how learning disabilities relate to reading comprehension. Different disabilities, whether related to reading or not, may have different effects on vocabulary skill and overall reading ability. Additionally, researchers will need to take into account how specific differences in the classroom, school, and school district can impact those with and without learning disabilities.

Citation: Quinn, J. M., Wagner, R. K., Petscher, Y., Roberts, G., Menzel, A. J., & Schatschneider, C. (2020). Differential codevelopment of vocabulary knowledge and reading comprehension for students with and without learning disabilities. Journal of Educational Psychology, 112(3), 608–627. https://doi.org/10.1037/edu0000382