Get Rhythm: Comorbidity between Dyslexia, SLI and Dysgraphia
Although Developmental Dyslexia (DD) is defined as a reading problem, children with DD have often undiagnosed problems with oral language and display a typical behavior and typical ERP responses observed in children with Specific Language Impairment (SLI).
Based on Italian, I report some data showing that children with DD fail in those areas in which also children with SLI fail (data will come from the investigation of clitic production, relative clauses comprehension, subject_verb_agreement processing).
In order to pin down the source of this comorbidity, I move to another area, in which children with DD appear to be weak. Subtle motor and handwriting problems have been observed in children with DD, although the issue is hotly disputed. In our study, we compared the handwriting performance of 17 children with Developmental Dyslexia (DD) (M age = 8;9, SD = 0,6), to that of 22 children with both DD and Dysgraphia (DD&DY) (M age = 9;05, SD = 1,14) and to that of 39 typical developed children (TD) (M age = 9;2, SD = 0,84). We also administered various language tasks. We found that children with DD were similar to children with DD&DY and were slower in writing and more dysfluent than TD children. We found that handwriting measures and language measures correlated. Interestingly, the analysis of the total duration of single letters in handwriting revealed that both children with DD and with DD&DY exhibited more variability than TD children.
We propose that handwriting difficulties stem from the interface between language and motor planning, and more specifically from impairment related to time estimation, that is crucial in order to transpose a linguistic structure into a sequence of motor events. We will speculate on the idea that children with DD (and likely SLI) may impaired in aspects of rhythmic activities that require time estimation for the production of linguistic events (syllable, phrases).