Specific Language Impairment and Reading Disability: Categorical Distinction or Continuum?

Specific language impairment (SLI) and reading disability (RD) are familial, moderately heritable comorbid developmental disorders. The key deficit of SLI is oral language, whereas children with RD exhibit impairment in learning to read. The present study examines the possible co-occurrence of RD and SLI and the nature of this co-occurrence at a linguistic and a cognitive level in an orthographically consistent language. Four groups of children participated in the study: an RD group (n = 10), an SLI group (n = 13), a possible comorbid group (n = 9), and a control–no deficit group (n = 20). Analysis showed that all three clinical groups in our sample performed similarly in phonological awareness and naming-speed tasks. However, significant group differences were observed in orthographic processing, reading, semantics, and phonological memory measures, thus supporting the view that SLI and RD are distinct disorders. Results are in line with previous findings indicating that SLI and RD share common characteristics, although the two conditions are manifested with different symptoms