Inconsistent Speech Categorization in School-Age Children with Language and Reading Disabilities

Both Developmental Language Disorder (DLD) and Reading Disorder (RD or dyslexia) have been proposed to derive in part from low-level speech perception deficits which may affect downstream language/reading processes. However, DLD and RD are comorbid, raising questions of whether the deficits in one group are driven by the other. Moreover, methodological limits of traditional forced-choice categorizations create uncertainty regarding the nature of the deficits. We examined speech categorization in children with language/reading disabilities, using a visual analog scaling task that overcomes these limits. Participants hear tokens from a speech continuum and indicate the degree of correspondence between the stimulus and each word by selecting a point on a continuous rating scale. Results revealed that children with poor language/reading exhibited similar long-term category structure to their peers with better abilities, but greater trial-to-trial categorization inconsistency. The categorization inconsistency has a unique effect on language/reading abilities, even after controlling for the potential mediating effect of phonological processing on language/reading. Importantly, children with poor reading showed high inconsistency specifically for vowels. These suggest that children’s language/reading abilities are more associated with the consistency of the perceptual processes.