Familial aggregation of spelling disability

This study examined the familial aggregation of spelling disability in a sample of 32 German school-aged children and their relatives. The influence of two different diagnostic criteria (low-achievement criterion, and regression-based IQ-discrepancy criterion) on the rate of affectedness was investigated. Results revealed that 52.3-61.9% of the sibs and 26-34% of the parents were spelling disabled. Little evidence was found for an influence of the diagnostic criterion on the rate of affectedness.