Parallels between the reading and spelling deficits of two subgroups of developmental dyslexics

The spelling errors of third graders who fit phonological andsurface profiles of developmental dyslexia were analyzed, alongwith the errors of younger (reading level matched) andchronologically age matched non-dyslexic comparison groups. InStudy 1, errors were analyzed as phonologically constrained,unconstrained, or inaccurate and as either orthographicallyacceptable or unacceptable. Study 2 extended the errorclassification system to nonword spellings. The main finding wasthat different types of dyslexics produced different types oferrors. Both studies found that children produced spelling errorsconsistent with their type of dyslexia. The phonological groupshowed poor knowledge of phoneme-grapheme correspondences,consistent with the existence of a phonological deficit. Thesurface group's spelling error profile differed from thephonological group and closely resembled the younger normalcomparison group. This pattern is consistent with other evidencethat surface dyslexia represents a general delay in acquiringliteracy skills. The studies provide converging evidence, from aspelling task, that developmental dyslexia is a non-homogeneouscategory consisting of at least two major subtypes with distinctetiologies and behavioral sequelae.