IQ CORRELATIONS IN TRANSRACIAL ADOPTIVE FAMILIES

IQ tests were administered to all available members over 4 years old i n 101 transracial adoptive families when the adopted children were an average of 7 years old and again when they averaged 17 years old. At b oth times, 426 members of 93 families were studied; 398 were seen in p erson and administered the WAIS-R or WISC-R. IQ correlations were calc ulated for adopted and biological parent-child pairs, and for genetica lly related and unrelated siblings. Educational levels of birth parent s were correlated with the IQ scores of their adopted-away children. R esults show that biologically related family members tended to resembl e each other intellectually more than did adoptive family members at b oth time points. IQ correlations for biological parent-child pairs exc eeded those for adoptive parent-child pairs, and correlations were gre ater for genetically related than unrelated siblings. In late adolesce nce, the IQ scores of unrelated siblings in the transracial adoptive f amilies were more similar than those of unrelated adolescent sibling p airs reported in other studies. The pattern of IQ correlations for unr elated siblings suggested that familial environmental influences on IQ decline from childhood to late adolescence, but this conclusion was n ot supported by parent-child IQ correlations. The effects of selective placement on familial IQ correlations were small. Estimates of geneti c and familial environmental influences on IQ were very similar to tho se of other studies. This suggests that the influences on intellectual development in this sample of black/interracial adoptees reared in wh ite families are similar to those for children in the majority populat ions of the United States and Western Europe.