The Minnesota Transracial Adoption Study examined the IQ test scores of 130 black or interracial children adopted by advantaged white families. The aim of the study was to determine the contribution of environmental and genetic factors to the poor performance of black children on IQ tests as compared to white children. The initial study was published in 1976 by Sandra Scarr and Richard A. Weinberg. A follow-up study was published in 1992 by Richard Weinberg, Sandra Scarr and Irwin D. Waldman. Another related study investigating social adjustment in a subsample of the adopted black children was published in 1996. The 1992 follow-up study found that "social environment maintains a dominant role in determining the average IQ level of black and interracial children and that both social and genetic variables contribute to individual variations among them." Background and study design On measures of cognitive ability (IQ tests) and school performance, black children in the U.S. have performed worse than white children. At the time of the study, the gap in average performance between the two groups of children was approximately one standard deviation, which is equivalent to about 15 IQ points or 4 grade levels at high school graduation. Thus, the average IQ score of black children in the U.S. was approximately 85, compared to the average score of white children of 100. No detectable bias due to test construction or administration had been found, although this does not rule out other biases. The gap is functionally significant, which makes it an important area of study. The Minnesota Transracial Adoption Study tried to answer whether the gap is primarily caused by genetic factors or whether it is primarily caused by environmental and cultural factors. The study was funded by the Grant Foundation and the National Institute of Child Health and Human Development. By examining the cognitive ability and school performance of both black and white children adopted into white families, the study intended to separate genetic factors from rearing conditions as causal influences in the gap. "Trans racial adoption is the human analog of the cross-fostering design, commonly used in animal behavior genetics research.... There is no question that adoption constitutes a massive intervention" (Scarr & Weinberg, 1976, p. 726). Scarr and Weinberg studied black, white, Asian, indigenous American, and mixed-race black/white children adopted by upper-middle-class white families in Minnesota. The average IQ of the adopting parents was more than one