Relationships among cognitive deficits and component skills of reading in younger and older students with developmental dyslexia.

Processing speed deficits along with phonological awareness deficits have been identified as risk factors for dyslexia. This study was designed to examine the behavioral profiles of two groups, a younger (6-8 years) and an older (10-15 years) group of dyslexic children for the purposes of (1) evaluating the degree to which phonological awareness and processing speed deficits occur in the two developmental cohorts; (2) determining the strength of relationships between the groups' respective mean scores on cognitive tasks of phonological awareness and processing speed and their scores on component skills of reading; and (3) evaluating the degree to which phonological awareness and processing speed serve as concurrent predictors of component reading skills for each group. The mean scaled scores for both groups were similar on all but one processing speed task. The older group was significantly more depressed on a visual matching test of attention, scanning, and speed. Correlations between reading skills and the cognitive constructs were very similar for both age-groups. Neither of the two phonological awareness tasks correlated with either of the two processing speed tasks or with any of the three measures of reading. One of the two processing speed measures served as a concurrent predictor of word- and text-level reading in the younger, however, only the rapid naming measure functioned as a concurrent predictor of word reading in the older group. Conversely, phonological processing measures did not serve as concurrent predictors for word-level or text-level reading in either of the groups. Descriptive analyses of individual subjects' deficits in the domains of phonological awareness and processing speed revealed that (1) both linguistic and nonlinguistic processing speed deficits in the younger dyslexic children occurred at higher rates than deficits in phonological awareness and (2) cognitive deficits within and across these two domains were greater in the older dyslexic children. Our findings underscore the importance of using rapid naming measures when testing school-age children suspected of having a reading disability and suggest that processing speed measures that do not reply on verbal responses may serve as predictors of reading disability in young children prior to their development of naming automaticity.