Minnesota Transracial Adoption Study
Encyclopedia
The Minnesota Transracial Adoption Study examined the IQ test scores
of 130 black
/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.
, 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. is approximately 85, compared to the average score of white children of 100. No detectable bias due to test construction or administration has 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 standard deviation
above the population mean of 100. The biological children of these parents were also tested. The sample of adopted children was selected by eligible parents contacting the researchers for participating following a newsletter call. The geographical origin of the adopted children was not uniform. All except one white adopted child was adopted in-state. Black and interracial children came from twelve states and Asian and indigenous American children came from Minnesota as well as from Korea, Vietnam, Canada and Ecuador.
As Scarr & Weinberg (1976) note, transracial adoption studies only control for family environment, not social environment. For example, children who are socially identified as black may still be subject to racial discrimination despite being raised by white parents. Yet, it was previously known that adoption into upper-middle class white families has a positive influence on the IQ and school performance of white children.
The study showed significant differences in adoption patterns of mixed-race black/white and black adopted children as was noted by Scarr and Weinberg (1976):
The adopting parents of 12 of the interracial children wrongly believed that their adopted children had two black parents. The average IQ of these 12 children was not significantly different from the scores of the 56 interracial children correctly classified by their adoptive parents as having one black and one white parent.
The study found that age at adoption was significantly associated with measured IQs:
Some have suggested that differing pre-adoption experiences, including age at adoption, explain the racial patterns in the results. Lee (2009) argues against this interpretation, pointing out that there is no evidence from other studies that variables such as age at adoption exert an effect on IQ lasting until late adolescence. In the Minnesota study, the proportion of IQ variance associated with pre-adoption variables declined from .32 to .13 between ages 7 and 17. Lee further suggests that causality may run from IQ and other behavioral variables to differences in pre-adoption experiences rather than the other way around, and that race by itself as a visible characteristic may have affected pre-adoption experience.
The average difference in IQ scores between the testing at age 7 and testing at age 17, seen in all groups, may be due to the use of different IQ tests. The original study used Stanford-Binet Form L-M, WISC
or WAIS
tests, depending on age, while the follow-up used WISC-R or WAIS-R. Weinberg, Scarr and Waldman point describe the effect of this change in test:
Furthermore the data needed to be corrected for the Flynn effect
as stated by Ulrich Neisser:
The data corrected for the Flynn effect
was published in 2000 by John Loehlin in the Handbook of Intelligence.
The analysis of structured interviews at age 7 and 17 reported by (DeBerry, Scarr & Weinberg 1996) found that about half of the studied black adopted children had adjustment difficulties. They had difficulties becoming competent in both European and African-American reference group orientation but had stronger affinity with European rather than African-American group. Stronger identification with one or the other group predicted better adjustment..
Both Levin (1994) and Lynn (1994) argued that the data clearly supports a hereditarian alternative: that the mean IQ scores and school achievement of each group reflected their degree of African ancestry. For all measures, the children with two black parents scored lower than the children with one black and white parent, who in turn scored lower than the adopted children with two white parents. Both omitted discussion of Asian adoptees.
Waldman, Weinberg, and Scarr (1994) responded to Levin (1994) and Lynn (1994). They noted that the data taken of adoption placement effects can explain the observed differences. But that they cannot make that claim firmly due to the pre adoption factors confounded racial ancestry, preventing an unambiguous interpretation of the results. They also note that Asian data fits that hypothesis while being omitted by both Levin and Lynn. They argued that,"contrary to Levin's and Lynn's assertions, results from the Minnesota Transracial Adoption Study provide little or no conclusive evidence for genetic influences underlying racial differences in intelligence and achievement." and note that "We think that it is exceedingly implausible that these differences are either entirely genetically based or entirely environmentally based. The true causes of racial-group differences in IQ, or in any other characteristic, are likely to be too complex to be captured by locating them on a single hereditarianism-environmentalism dimension." On the question of Arthur Jensen (1998) examined these studies and reviewed the evidence that adoption does not affect children's IQ scores after age 7.
In a 1998 article, Scarr wrote: "The test performance of the Black/Black adoptees [in the study] was not different from that of ordinary Black children reared by their own families in the same area of the country. My colleagues and I reported the data accurately and as fully as possible, and then tried to make the results palatable to environmentally committed colleagues. In retrospect, this was a mistake. The results of the transracial adoption study can be used to support either a genetic difference hypothesis or an environmental difference one (because the children have visible African ancestry). We should have been agnostic on the conclusions [...]."
Loehlin (2000) reiterates the confounding problems of the study and notes that both genetic and environmental interpretations are possible. He further offers another possible explanation of the results, namely unequal prenatal factors: "[O]ne possibility lies in the prenatal environment provided by Black and White biological mothers. The Black-Black group, of course, all had Black mothers. In the Black-White group, virtually all of the birth mothers were White (66 of 68). Willerman and his colleagues found that in interracial couples it made a difference whether the mother was Black or White: The children obtained higher IQs if she was White. They suspected that this difference was due to postnatal environment, but it could, of course, have been in the prenatal one."
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...
of 130 black
Black people
The term black people is used in systems of racial classification for humans of a dark skinned phenotype, relative to other racial groups.Different societies apply different criteria regarding who is classified as "black", and often social variables such as class, socio-economic status also plays a...
/interracial
Multiracial
The terms multiracial and mixed-race describe people whose ancestries come from multiple races. Unlike the term biracial, which often is only used to refer to having parents or grandparents of two different races, the term multiracial may encompass biracial people but can also include people with...
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
Sandra Scarr
- Biography :Born in Maryland, her family followed her father, who was stationed at the United States Army's largest chemical weapon facility through much of her childhood. Scarr earned her Ph.D...
and Richard A. Weinberg
Richard A. Weinberg
Richard A. Weinberg is an American psychology professor.For most of his career, Weinberg has taught at University of Minnesota after earning his Ph.D there in 1968. He is known for his Minnesota Transracial Adoption Study with Sandra Scarr...
. 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.
Background and study design
On measures of cognitive ability (IQ tests) and school performance, black children in the U.S. perform worse than white children. The gap in average performance between the two groups of children is approximately one standard deviationStandard deviation
Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...
, 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. is approximately 85, compared to the average score of white children of 100. No detectable bias due to test construction or administration has 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
National Institute of Child Health and Human Development
The Eunice Kennedy Shriver National Institute of Child Health and Human Development , created by Congress in 1962, supports and conducts research on topics related to the health of children, adults, families, and populations...
.
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
Adoption
Adoption is a process whereby a person assumes the parenting for another and, in so doing, permanently transfers all rights and responsibilities from the original parent or parents...
is the human analog of the cross-fostering design, commonly used in animal behavior genetics research.... There is no question that adoption
Adoption
Adoption is a process whereby a person assumes the parenting for another and, in so doing, permanently transfers all rights and responsibilities from the original parent or parents...
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
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
. The average IQ of the adopting parents was more than one standard deviation
Standard deviation
Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...
above the population mean of 100. The biological children of these parents were also tested. The sample of adopted children was selected by eligible parents contacting the researchers for participating following a newsletter call. The geographical origin of the adopted children was not uniform. All except one white adopted child was adopted in-state. Black and interracial children came from twelve states and Asian and indigenous American children came from Minnesota as well as from Korea, Vietnam, Canada and Ecuador.
As Scarr & Weinberg (1976) note, transracial adoption studies only control for family environment, not social environment. For example, children who are socially identified as black may still be subject to racial discrimination despite being raised by white parents. Yet, it was previously known that adoption into upper-middle class white families has a positive influence on the IQ and school performance of white children.
The study showed significant differences in adoption patterns of mixed-race black/white and black adopted children as was noted by Scarr and Weinberg (1976):
It is essential to note, however, that the groups also differed significantly (p < .05) in their placement histories and natural mother's education. Children with two black parents were significantly older at adoption, had been in the adoptive home a shorter time, and had experienced a greater number of preadoption placements. The natural parents of the black/black group also averaged a year less of education than those of the black/white group, which suggests an average difference between the groups in intellectual ability. There were also significant differences between the adoptive families of black/black and black/white children in father's education and mother's IQ.
Results
The children were first tested in 1975 at age 7. In 1985, 196 of the original 265 children were retested at age 17.| Children's background | Age 7 IQ | Age 17 IQ | Age 17 GPA | Age 17 class rank (percentile Percentile In statistics, a percentile is the value of a variable below which a certain percent of observations fall. For example, the 20th percentile is the value below which 20 percent of the observations may be found... ) |
Age 17 school aptitude (percentile Percentile In statistics, a percentile is the value of a variable below which a certain percent of observations fall. For example, the 20th percentile is the value below which 20 percent of the observations may be found... ) |
|---|---|---|---|---|---|
| Adopting parents tested when children were 7 and 17 | 120 | 115 | — | — | — |
| Non adopted, with two white biological parents | 116 | 109 | 3.0 | 64 | 69 |
| Adopted, with two white biological parents | 118 | 106 | 2.8 | 54 | 59 |
| Adopted, with one white and one black biological parent | 110 | 99 | 2.2 | 40 | 53 |
| Adopted, with Asian or indigenous American parents | 101 | 96 | — | — | — |
| Adopted, with two black biological parents | 95 | 89 | 2.1 | 36 | 42 |
The adopting parents of 12 of the interracial children wrongly believed that their adopted children had two black parents. The average IQ of these 12 children was not significantly different from the scores of the 56 interracial children correctly classified by their adoptive parents as having one black and one white parent.
The study found that age at adoption was significantly associated with measured IQs:
| Children's background | Age 7 IQ | Age 17 IQ |
|---|---|---|
| Early placed adopted children | 111 | 99 |
| Late placed adopted children | 97 | 92 |
Some have suggested that differing pre-adoption experiences, including age at adoption, explain the racial patterns in the results. Lee (2009) argues against this interpretation, pointing out that there is no evidence from other studies that variables such as age at adoption exert an effect on IQ lasting until late adolescence. In the Minnesota study, the proportion of IQ variance associated with pre-adoption variables declined from .32 to .13 between ages 7 and 17. Lee further suggests that causality may run from IQ and other behavioral variables to differences in pre-adoption experiences rather than the other way around, and that race by itself as a visible characteristic may have affected pre-adoption experience.
The average difference in IQ scores between the testing at age 7 and testing at age 17, seen in all groups, may be due to the use of different IQ tests. The original study used Stanford-Binet Form L-M, WISC
WISC
WISC may refer to:* Wechsler Intelligence Scale for Children* WISC-TV, a television station licensed to Madison, Wisconsin, United States* Wisconsin Integrally Synchronized Computer* writable instruction set computer...
or WAIS
WAIS
WAIS may refer to:* West Antarctic Ice Sheet* Wechsler Adult Intelligence Scale* Wide area information server * WAIS , a radio station licensed to Buchtel, Ohio, United States...
tests, depending on age, while the follow-up used WISC-R or WAIS-R. Weinberg, Scarr and Waldman point describe the effect of this change in test:
Declines in IQ scores have been documented when individuals are retested on a revised form of an original measure, as well as when a test used at a first administration was normed earlier than a test used at a subsequent administration (see Flynn, 1984, for a review). For example, the decline in Full-Scale IQ score from the WAIS to the WAIS-R averaged 6.8 points across a number of studies (reviewed by Sattler, 1988) and was 7.5 points in a sample of 72 35-44-year-olds tested as part of the standardization of the WAIS-R (Wechsler, 1981). This is precisely the test combination used for adoptive parents in our study.
Furthermore the data needed to be corrected for the Flynn effect
Flynn effect
The Flynn effect is the name given to a substantial and long-sustained increase in intelligence test scores measured in many parts of the world. When intelligence quotient tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100...
as stated by Ulrich Neisser:
Everyone involved in this debate is well-aware that such comparisons must be corrected for the Flynn effectFlynn effectThe Flynn effect is the name given to a substantial and long-sustained increase in intelligence test scores measured in many parts of the world. When intelligence quotient tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100...
: Mean scores on all standard IQ tests seem to rise steadily at about 0.3 points per year. In the Minnesota study, where the tests used in the follow-up were generally not the same as those that had been given the first time, these corrections are complex and must be made on an individual basis. Until they have been made–Waldman et al. reported that they are in progress–raw figures like those above are relatively meaningless.
The data corrected for the Flynn effect
Flynn effect
The Flynn effect is the name given to a substantial and long-sustained increase in intelligence test scores measured in many parts of the world. When intelligence quotient tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100...
was published in 2000 by John Loehlin in the Handbook of Intelligence.
| Children's background | Number of Children | Age 7 Corrected IQ | Age 17 Corrected IQ |
|---|---|---|---|
| Non adopted, with two white biological parents | 101 | 110.5 | 105.5 |
| Adopted, with two white biological parents | 16 | 111.5 | 101.5 |
| Adopted, with one white and one black biological parent | 55 | 105.4 | 93.2 |
| Adopted, Asian or indigenous American parents | 12 | 96.1 | 91.2 |
| Adopted, with two black biological parents | 21 | 91.4 | 83.7 |
The analysis of structured interviews at age 7 and 17 reported by (DeBerry, Scarr & Weinberg 1996) found that about half of the studied black adopted children had adjustment difficulties. They had difficulties becoming competent in both European and African-American reference group orientation but had stronger affinity with European rather than African-American group. Stronger identification with one or the other group predicted better adjustment..
Interpretations
Scarr & Weinberg (1976) interpreted the results from age 7 suggesting that racial group differences in IQ are inconclusive due to confounding of the study. They noted however that the study indicated that cross-racial adoptive had a positive effect on black adopted children. In support of this interpretation, they drew special attention to the finding that the average IQ of "socially classified" black children was greater than the U.S. white mean. The followup data was collected in 1986 and Weinberg et al. published their findings in 1992 and interpreted their results still supporting the original conclusions.Both Levin (1994) and Lynn (1994) argued that the data clearly supports a hereditarian alternative: that the mean IQ scores and school achievement of each group reflected their degree of African ancestry. For all measures, the children with two black parents scored lower than the children with one black and white parent, who in turn scored lower than the adopted children with two white parents. Both omitted discussion of Asian adoptees.
Waldman, Weinberg, and Scarr (1994) responded to Levin (1994) and Lynn (1994). They noted that the data taken of adoption placement effects can explain the observed differences. But that they cannot make that claim firmly due to the pre adoption factors confounded racial ancestry, preventing an unambiguous interpretation of the results. They also note that Asian data fits that hypothesis while being omitted by both Levin and Lynn. They argued that,"contrary to Levin's and Lynn's assertions, results from the Minnesota Transracial Adoption Study provide little or no conclusive evidence for genetic influences underlying racial differences in intelligence and achievement." and note that "We think that it is exceedingly implausible that these differences are either entirely genetically based or entirely environmentally based. The true causes of racial-group differences in IQ, or in any other characteristic, are likely to be too complex to be captured by locating them on a single hereditarianism-environmentalism dimension." On the question of Arthur Jensen (1998) examined these studies and reviewed the evidence that adoption does not affect children's IQ scores after age 7.
In a 1998 article, Scarr wrote: "The test performance of the Black/Black adoptees [in the study] was not different from that of ordinary Black children reared by their own families in the same area of the country. My colleagues and I reported the data accurately and as fully as possible, and then tried to make the results palatable to environmentally committed colleagues. In retrospect, this was a mistake. The results of the transracial adoption study can be used to support either a genetic difference hypothesis or an environmental difference one (because the children have visible African ancestry). We should have been agnostic on the conclusions [...]."
Loehlin (2000) reiterates the confounding problems of the study and notes that both genetic and environmental interpretations are possible. He further offers another possible explanation of the results, namely unequal prenatal factors: "[O]ne possibility lies in the prenatal environment provided by Black and White biological mothers. The Black-Black group, of course, all had Black mothers. In the Black-White group, virtually all of the birth mothers were White (66 of 68). Willerman and his colleagues found that in interracial couples it made a difference whether the mother was Black or White: The children obtained higher IQs if she was White. They suspected that this difference was due to postnatal environment, but it could, of course, have been in the prenatal one."
See also
- Interracial adoptionInterracial adoptionInterracial adoption refers to the act of placing a child of one racial or ethnic group with adoptive parents of another racial or ethnic group....
- Twin studyTwin studyTwin studies help disentangle the relative importance of environmental and genetic influences on individual traits and behaviors. Twin research is considered a key tool in behavioral genetics and related fields...
- Heritability of IQ
- Race and intelligenceRace and intelligenceThe connection between race and intelligence has been a subject of debate in both popular science and academic research since the inception of intelligence testing in the early 20th century...