The double-deficit hypothesis in Spanish developmental dyslexia

Abstract

This study was designed to explore the double-deficit hypothesis (DDH) of developmental dyslexia in a sample of 133 Spanish children between the ages of 7 and 12 years. Four groups were formed on the basis of their performance in phonemic awareness and rapid automatized naming (RAN): (1) one group with low performance in naming speed (NS), but average in phonological awareness (PA; naming deficit subtype); (2) a second group with low performance in PA, but normal in NS (phonological deficit subtype); (3) a third group with low performance in both variables (double-deficit subtype); and (4) a fourth group with no deficit in PA and NS (control group). The four groups were compared on measures of lexical access (naming word and pseudowords), fluency, orthographic abilities, and reading comprehension. The double-deficit subtype showed the most difficulties with reading, and the presence of deficit in RAN in naming deficit subtype affected measures of fluency but not orthographic abilities. However, fewer differences were noted between single-deficit subgroups. These results are partially consistent with the predictions of the DDH.