Eyferth study

The Eyferth study is the name often given to a study conducted by psychologist Klaus Eyferth concerning the IQs of white and racially mixed children in post-Second World War West Germany. The mothers of the children studied were white German women, while their fathers were white and African-American members of the US occupation forces. In contrast to results obtained in many American studies, the average IQs of the children studied were roughly similar across racial groups, making the study an oft-cited piece of evidence in the debate about race and intelligence.

Eyferth's study was published under the title Eine Untersuchung der Neger-Mischlingskinder in Westdeutschland in the journal Vita Humana in 1959.

Study design
The children studied had been raised by their unmarried German mothers. All of the fathers, white or black, had been members of the US occupation forces stationed in Germany. At the time of the study, the children were aged between 5 and 13 (mean age: 10). The mothers of the children were approximately matched for socio-economic status; they were mostly of low SES. There were about 98 mixed race (black-white), and about 83 white children in the sample.

For assessing IQ, a German version of the WISC intelligence test (Hamburg Wechsler Intelligence Scale for Children, HAWIK) was used.

Results
The white children studied averaged an IQ of 97.2, whereas the average of the racially mixed children was 96.5.

Sorted out by sex and race, the average scores obtained were as follows:

"Environmentalists"
Stressing the similarity of average IQ scores across racial groups in the Eyferth study, Jim Flynn, Richard E. Nisbett, Nathan Brody, and others have interpreted it as supporting the notion that IQ differences between whites and blacks observed in many other studies are wholly cultural or environmental in origin. Moreover, they have pointed out that mixed-race children may have faced prejudice growing up as a racial minority, making the similarity of results even more significant.

"Hereditarians"
Several other researchers have been skeptical about the value of the study for illuminating the causes of racial IQ differences.

Arthur Jensen has pointed out that the white girls in the study obtained an average IQ eight points below that of the white boys, suggesting a sampling error, because in the WISC standardization sample the average IQs of boys and girls are equal (among the mixed-race subjects in the Eyferth study, there was a small sex difference of 1 point, favoring boys). He has also noted that the IQs of the children's mothers and fathers are unknown, and that white and black G.I.'s in Germany were not equally representative of their respective populations, since about 30 percent of blacks, compared to about 3 percent of whites, failed the preinduction mental test and were not admitted into the armed forces. He further argues that the selective preferences of the German women with regard to sexual partners may have influenced the results in an unknown manner. Moreover, nearly all of the children were tested before adolescence, i.e. before the genotypic aspect of IQ has become fully manifested. Finally, Jensen suggests that heterosis may have enhanced the IQ level of the mixed race children in the study.

Rushton and Jensen have further pointed out that 20–25% of the fathers in the study were not African Americans but rather French North Africans.