Students diagnosed with specific learning disabilities struggle with spelling accuracy, but they do so for different reasons. For instance, students with dysgraphia, dyslexia, and oral-written language learning disability (OWL-LD) have distinct areas of weakness in cognitive processing and unique difficulties with the linguistic features necessary for accurate spelling (Silliman & Berninger, 2011). This project considered the spelling errors made by such students to determine if their unique learning profiles lead to distinct misspelling patterns. Academic summaries handwritten by 33 students diagnosed with dysgraphia (n=13), dyslexia (n=15), and OWL-LD (n=5) were analyzed for type/complexity and number of spelling errors. Additionally, the differences in error frequency and complexity were analyzed based on whether academic material had been listened to or read. Misspellings were extracted from the students' essays and evaluated using an unconstrained linguistic scoring system (POMAS). Then, the complexity/severity of the misspelling was computed using a complexity metric (POMplexity). Statistical results revealed that children within the diagnostic categories of dysgraphia, dyslexia, and OWL-LD appear to produce errors that are similar in complexity and frequency. Hence, students with specific learning disabilities do not appear to make patterns and numbers of errors specific to their diagnosis. Additionally, statistical results indicated that all students produced similar numbers of errors in both the reading and listening conditions, indicating that the mode of presentation did not affect spelling accuracy. When spelling errors were analyzed qualitatively, some differences across diagnostic categories and variability within groups was noted. Students with dysgraphia produced misspellings involving a phoneme addition or omission. Phonological and orthographic errors typical of younger children were characteristic of misspellings produced by students with dyslexia. Individuals with OWL-LD tended to omit essential vowels and were more likely to misspell the same word in multiple different ways. Overall, these results indicate that the subcategories of dysgraphia, dyslexia, and OWL-LD represent of gradients of impairment within the overarching category of specific learning disabilities. However, even within those subcategories, there is a wide degree of variability. Diagnostic categories, then, may suggest areas of linguistic weakness, but subcategories alone cannot be used for determining the nature of spelling intervention.

In order to spell fluently and accurately, phonology, orthography, and morphology must be integrated and stored into long term memory (Berninger & Richards, in press; Berninger, Nagy, Tanimoto, Thompson, Abbott, 2015). Children with dysgraphia, dyslexia, and OWL-LD have specific deficits in linguistic processing that impede the cross-mapping of these linguistic elements. This study analyzes the frequency and nature of spelling errors produced by children with dysgraphia, dyslexia, and OWL-LD during an academic writing task in order to determine if known deficits in linguistic processing affect the type and severity of spelling errors made by these children. The present study analyzed error severity and frequency of spelling errors produced by children with dysgraphia (n=13), dyslexia (n=17), or OWL-LD (n=5) during the academic writing tasks obtained in the Berninger et al. (2015) study. In the previous study, students read or listened to computerized lessons about basic mathematical concepts and then typed summaries of what they learned. For the current study, all spelling errors made during the typed summary writing tasks were extracted and analyzed using the Phonological, Orthographic, Morphological Assessment of Spelling (POMAS) and then recoded with POMplexity (a measure of error severity) to determine the severity and frequency of spelling errors made in the linguistic categories of phonology, orthography, and morphology. Results indicated that the students did not differ in error severity by diagnostic category. However, a qualitative analysis using the POMAS revealed that children from different diagnostic categories produced different types of errors. With respect to error frequency, only students with dysgraphia made significantly fewer errors than students with OWL-LD, and all participants, regardless of diagnostic category produced more errors in typed summaries following the reading condition. These results are consistent with previous research indicating that children with learning disabilities do not produce deviant spelling errors when compared to typically-developing, age-matched peers or typically-developing, spelling-matched peers (Silliman, Bahr, and Peters, 2006, among others). The current results demonstrate that the spelling errors of children with learning disabilities reflect the expected linguistic breakdowns in cross-code mapping, and that children with learning disabilities may display these spelling deficits beyond an appropriate age.