Consonant-vowel lateralization in dyslexic children: deficit or compensatory development?
Two studies with the same subjects examined dyslexic children's puzzling superiority in forced left ear (LE) dichotic recall with consonant-vowel (CV) combinations. Thirty dysphonemic dyslexics were compared to 30 age-matched and 30 younger reading-matched normal readers. The children were tested in directed attention dichotic listening and in pseudoword decoding, word recognition, reading comprehension, spelling, arithmetic, and general intelligence (IQ). Failure to replicate the LE effect in the first experiment or in free-recall trials suggests its probable origin in aberrant attention/arousal rather than in deviant verbal lateralization. Experiment two replicated the superior LE effect in comparison to both control groups but also found the dyslexics poorer at the right ear (RE). Laterality coefficients confirmed that the dyslexics were more weakly lateralized. Corrections for stimulus dominance revealed that the uncorrected scores (1) concealed the extreme difficulty of the task and (2) obscured floor effects in the LE performance of the normals. Correlations suggest cautiously that CV lateralization may be associated inversely with reading comprehension and word decoding in the dyslexics and normal readers. The results provide mild support for the hypothesis that weak attentional lateralization for CVs in dyslexia may result from the precocious development of posterior right hemisphere attentional systems in compensation for presumed posterior left hemisphere lesions. No support was found for the competing hypothesis that such weak lateralization may be a component of the dyslexics' primary, correlated, or secondary deficit symptomatology.
Kershner
J
J
Ontario Institute for Studies in Education, University of Toronto, Canada.
Micallef
J
J
D001921:Brain / Q000503:physiopathology; D002648:Child; D003337:Corpus Callosum / Q000503:physiopathology; D004007:Dichotic Listening Tests; D004410:Dyslexia / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007804:Language Development; D008297:Male; D013060:Speech / Q000502:physiology*; D013063:Speech Discrimination Tests; D013067:Speech Perception / Q000502:physiology*; D014888:Wechsler Scales