Verbal deficits in children with 47, XXY and 47, XXX karyotypes: A descriptive and experimental study

This study examines the intellectual abilities of children with a supernumerary X chromosome complement. In the first part, 33 boys and 13 girls, who were ascertained through a neonatal screening project, were given a WISC-R. Comparisons with siblings revealed a significant deficit in the verbal ability of the extra X children while their nonverbal skills were normal. The second part investigated the specific verbal impairments of these children with a sentence verification task. The results of comparisons with normal children indicated poorer performance by the supernumerary X groups, particularly on the more difficult task items. Correlations between measures indicated that verbal IQ was more strongly related to sentence verification performance than performance IQ. The final section deals with some of the biological factors that may contribute to the verbal deficits in these children. The results indicate that the most verbally impaired children were those with the greatest delays in physical growth, as indicated by bone age and dermatoglyphic measures. These findings are discussed in terms of the influence of chromosomally determined growth rates upon the brain, its maturity, and consequent capacity to develop specific cognitive functions.