Dichotic listening and school performance in dyslexia

This study focused on the relationship between school performance and performance on a dichotic listening (DL) task in dyslexic children. Dyslexia is associated with impaired phonological processing, related to functions in the left temporal lobe. DL is a frequently used task to assess functions of the left temporal lobe. Due to the predominance of the contralateral neuronal pathways, a right ear advantage in the DL task reflects the superior processing capacity for the right ear stimulus in the left hemisphere (Kimura, 1963). Previous studies using DL in dyslexia are, however, inconclusive, and may reflect degree of severity of dyslexia. The aim of the present study was therefore to investigate lateralized processing in two sub-groups of dyslexia, differing in symptom severity. Two groups of dyslexic 12-year-old children and an age-matched control group were tested with a consonant-vowel DL task. The two dyslexia groups differed in severity through how they responded to training efforts being made in their schools, while otherwise being matched for age, IQ and diagnosis. The D1 (respondent group) group showed a DL performance pattern similar to the control group, i.e. a right ear advantage, while the D2 (non-respondent) group failed to show a right ear advantage on the DL task. The performance on the DL task by the two dyslexia groups may provide better insight as to the degree of reading and writing impairment in dyslexia. 'Cracking the code' and acquiring automatized literacy skills may seem harder for the D2 group children compared to the D1 children. Also, the present study points to the use of DL as a valid assessment tool in clinical work to improve differential diagnoses, particularly in relation to measures of school performance.