tokens: Significant IQ differences were found between ( 1 ) all 55 DM subjects ( mean 90 . 2 , SD 16 . 1 ) and 31 controls ( 102 . 6 , SD 9 . 4 ) , with no sex differences in either group ; ( 2 ) 15 affected parents ( 99 . 3 , SD 12 . 2 ) and their affected children ( 88 . 1 , SD 17 . 2 ) , where significance was dependent on parental sex being female ; and ( 3 ) 15 pairs of affected sibs ( 89 . 6 , SD 13 . 2 ) and their normal sibs ( 100 . 2 , SD 7 . 6 ) .