Hmmm...NYT has a person with Down's syndrome actually speak...don't they know that parents whose test is positive are told these children will never speak walk or care for themselves? (or are called "profoundly" retarded, when they are actually mild to moderately retarded).
Having Down's usually means your IQ is thirty points lower than your parents...so the range is variable...but since they are rarely "aggressive", often their intellect was overlooked..