The validity of discrepancy-based definitions of reading disabilities.

This study addressed the validity of distinguishing children with reading disabilities according to the presence or absence of discrepancies between intelligence test scores and academic achievement. Three definitions of reading disability were used to provide criteria for five groups of children who (a) met a discrepancy-based definition uncorrected for the correlation of IQ and achievement; (b) met a discrepancy-based definition correcting for the correlation of IQ and achievement; (c) met a low achievement definition with no IQ discrepancy; (d) met criteria a and b; and (e) met none of the criteria and had no reading disability. Comparison of these five groups on a set of 10 neuropsychological tests corrected for correlations with IQ showed that group differences were small and accounted for little of the variability among groups. These results question the validity of segregating children with reading deficiencies according to discrepancies with IQ scores.