Estimated Full-Scale IQ (FSIQ) distribution for females with 47,XXX compared to controls. In 47,XXX, there is a wide variation in IQ with the normal curve shifted to the left with the mean FSIQ at 85-90. The majority of females with 47,XXX have a FSIQ in the normal range, and many are above average compared to the general population. However, due to the shift of the curve, a larger percentage of females with 47,XXX fall in the intellectual disability range compared to controls. Adapted and reprinted with permission from Bender et. al. 1986 .