Cognitive abilities in reading-disabled children: a longitudinal study.

Longitudinal psychometric test data collected at two different ages (9.4 +/- 1.3 and 14.8 +/- 1.2 years) were utilized to compare the developmental rates of 69 pairs of reading-disabled and matched control children. Results of a two-factor (GROUP X TIME), mixed-model, multivariate analysis of variance indicated that reading-disabled children manifested deficits on measures of academic achievement, symbolic processing speed and spatial reasoning abilities at both ages. Although both reading-disabled and control children were found to improve significantly between the two testing sessions, the lack of a significant GROUP X TIME interaction on measures of academic achievement and spatial reasoning abilities indicated that the rate of development was similar for the two groups. For measures of symbolic processing speed, however, differences between reading-disabled and control children were somewhat greater at the later age.