Groups of 270 Black and 270 White children drawn from the national stratified random sample used in the standardization of the Wechsler Intelligence Scale for Children-Revised (WISC-R) were matched on age, sex, and WISC-R Full-Scale Intelligence Quotient to facilitate investigation of the patterns of specific cognitive abilities. (Author)

This final report reviews the second phase of a life-span study of boys with fragile X syndrome (FSX), the most common known inherited cause of mental retardation. Males with the syndrome are more severely affected than females and in males, delays are usually evident in all the developmental domains, although cognitive and communication skills…