Dutch Dyslexia in Adulthood: Core Features and Variety

Abstract

This study tested the phonological core deficit hypothesis among Dutch dyslexic adults and also evaluated the pattern of individual differences among dyslexics predicted by the phonological-core variable-orthographic differences (PCVOD) model (van der Leij & Morfidi, 2006 Bekebrede, J. I., van der Leij, A., Plakas, A. and Schijf, T. 2006. Interactieve Dyslexie Test [Interactive Dyslexia Test]: Experimental version, Uithoorn, , the Netherlands: Muiswerk Educatief. [Google Scholar]) in a sample of 57 control adults and 56 dyslexic adults. It was confirmed that Dutch adult dyslexics share a phonological core deficit. As predicted, there was significantly larger variability among dyslexics in orthographic coding relative to phonological coding. Orthographic coding also explained additional variance in word reading fluency after phonological coding was partialled out. Consistent with the PCVOD model, when two subgroups were selected, which differed in levels of orthographic coding, the high-scoring subgroup outperformed the low-scoring subgroup on almost all reading and reading-related tasks. As anticipated, the high-scoring subgroup had near-normal levels of orthographic abilities. These advantages were not attributable to differences in general cognitive competence, print exposure, or educational attainment.