and 106.7 performance IQ, while their siblings had an average 112.9 verbal IQ and 114.6 performance IQ.

Approximately half of 47,XYY boys identified by newborn screening programs had learning difficulties--a higher proportion than found among siblings and above-average-IQ control groups. In Edinburgh, 54% of 47,XYY boys (7 of 13) identified in a newborn screening program received remedial reading teaching compared to 18% (4 of 22) in an above-average-IQ control group of 46,XY boys matched by their father's social class. In Boston,