The nature of intelligence in adults with Down syndrome: IQ distribution and sex differences

Abstract

Normative data on intelligence in adults with Down syndrome was collected on 93 males and 80 females, aged 16 years and above, who had been given the Suzuki-Binet Intelligence Scale. Both the male and female groups showed bimodal curves in the distributions of IQs. Only for the low IQ groups, the distributions were defined by binomial distributions. The mean ages of starting to walk for the low IQ groups were six months or more later than those for the high IQ groups. However, no significant differences were observed in birthweights, terms of pregnancy, and ages between the two groups. In addition, significant sex differences were found in mean IQs, females scored higher in both the two groups.