"One of the most powerful direct studies of race and environment was
conducted by psychologists Sandra Scarr, Richard Weinberg and I. D. Waldman.
All three were quite well-known for their environmental opinions. The study
analyzed White, Black, and Mixed-race adopted children in more than 100
White families in Minnesota. The study was an egalitarian's dream, because
the children's adoptive parents had prestigious levels of income and
education and were anti-racist enough to adopt a Black child into their own
family. Scarr is a strong defender of racial equality and maintained that
environment played an almost exclusive role in IQ differences between the
races. Scarr supports the importance of heredity in causing individual
differences within a race, but she has argued that between-race differences
are mostly environmental.

   The children in the study included Whites, Blacks, and Mulattos as well
as the biological children of the White adoptive couples. At the age of 7,
the children were tested for IQ, and all of the groups including the Blacks
and Mulattos, scored above average in IQ. Scarr and Weinberg published a
paper claiming to have proven the almost exclusive power of environment over
race in IQ, even though they had to admit that the White children, whether
adopted or not, scored well above the Black and Mulatto children and that
the Mulatto children scored above the Blacks. (88)

   A decade later, when the children reached the age of 17, a follow-up
study was conducted that that again included IQ measurements. As they
matured, Black children had dropped back to an average of 89 in IQ, which is
the average IQ for Blacks in the region of the United States where the study
was done. The White adopted children scored an average of 106 in IQ, 17
points higher than the Black children, which is consistant with traditional
studies of Black and White IQ differences. In line with genetic theory the
half-White, half-Black Mulatto adopted children scored almost exactly
between the adopted Whites and Blacks. (89)

  RESULTS OF MINNESOTA TRANSRACIAL ADOPTION STUDY

                                                                IQ

        Parental IQ                                        115.35
        Biological Children                             109.4
       White Adopted children                      105.6
        Mulatto parents adopted children        98.5
        Black parents adopted children             89.4

     Scarr and Wienberg reluctantly published their data from the follow up
survey, but they waited close to four years to do so, almost as if they were
embarrassed by what they had found. Through a tortured reasoning process,
they still argued that environment played a dominant role in IQ. But in
their follow-up survey, unlike their first paper, they also admitted that
genes had an important impact as well. Both Richard Lynn and Michael Levin
effectively showed in their re-analysis of Scarr's own data, that genes
clearly comprise the dominant role in intelligence levels of those adopted
children. (90) (91)"

(88)  Scarr, S, & Weinberg R. A. (1976). IQ Test Perfomance of Black
Children Adopted By  White Families. American Psychologist. Vol. 31.
p.26-739

(89)  Weinberg, R. A. , Scarr, S., & Waldman, I. D. (1992). The Minnesota
Transracial Adoption Study. A Follow-Up of IQ Test Performance at
Adolescence, Intelligence. Vol 16.
p.17-135

(90)  Lynn, R. (1994). Reinterpretations Of The Minnesota Transracial
Adoption Study. Intelligence. Vol. 19. p.1-27

(91)  Levin, M. (1994). Comment on The Minnesota Transracial Adoption Study.
Intelligence Vol. 19. p.3-20