Can you spell dyslexia without SLI? Comparing the cognitive profiles of dyslexia and specific language impairment and their roles in learning

Abstract

The aim of the present study is to explore whether those with Specific Language Impairment (SLI) and dyslexia display distinct or overlapping cognitive profiles with respect to learning outcomes. In particular, we were interested in two key cognitive skills associated with academic performance - working memory and IQ. We recruited three groups of children - those with SLI, those with dyslexia, and a control group. All children were given standardized tests of working memory, IQ (vocabulary and matrix), spelling, and math. The pattern of results suggests that both children with dyslexia and SLI are characterized with poorer verbal working memory and IQ compared to controls, but preserved nonverbal cognitive skills. It appears that that these two disorder groups cannot be distinguished by the severity of their cognitive deficits. However, there was a differential pattern with respect to learning outcomes, where the children with dyslexia rely more on visual skills in spelling, while those with SLI use their relative strengths in vocabulary. These findings can have important implications for how intervention is tailored in the classroom, as disorder-specific support could yield important gains in learning.

Keywords: Academic attainment; Dyslexia; IQ; Learning needs; Specific language impairment; Working memory.