The second deficit: An investigation of the independence of phonological and naming-speed deficits in developmental dyslexia

An increasing body of dyslexia researchdemonstrates, in addition to phonologicaldeficits, a second core deficit in theprocesses underlying naming speed. Thehypothesized independence of phonologicalawareness and naming-speed variables inpredicting variance in three aspects of readingperformance was studied in a group of 144severely-impaired readers in Grades 2 and 3. Stepwise regression analyses were conducted onthese variables, controlling for the effects ofSES, age, and IQ. Results indicated thatphonological measures contribute more of thevariance to those aspects of reading skill thatinvolve decoding or word attack skills;naming-speed measures contribute more to skillsinvolved in word identification. Subtypeclassification findings were equally supportiveof the independence of the two deficits: 19%of the sample had single phonological deficits;15% had single naming-speed deficits; 60% had double-deficits; and 6% could not be classified. The implications of these findingsfor diagnosis and intervention are discussed.