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发信人: twinlight198 (雙灯), 信区: Military
标 题: Race differences in average IQ are largely genetic
发信站: BBS 未名空间站 (Mon May 20 22:37:57 2013, 美东)
Race differences in average IQ are largely genetic
Published on April 26, 2005 at 5:29 PM · 122 Comments
inShare.2A 60-page review of the scientific evidence, some based on state-
of-the-art magnetic resonance imaging (MRI) of brain size, has concluded
that race differences in average IQ are largely genetic.
The lead article in the June 2005 issue of Psychology, Public Policy and Law
, a journal of the American Psychological Association, examined 10
categories of research evidence from around the world to contrast "a
hereditarian model (50% genetic-50% cultural) and a culture-only model (0%
genetic-100% cultural)."
The paper, "Thirty Years of Research on Race Differences in Cognitive
Ability," by J. Philippe Rushton of the University of Western Ontario and
Arthur R. Jensen of the University of California at Berkeley, appeared with
a positive commentary by Linda Gottfredson of the University of Delaware,
three critical ones (by Robert Sternberg of Yale University, Richard Nisbett
of the University of Michigan, and Lisa Suzuki & Joshua Aronson of New York
University), and the authors' reply.
"Neither the existence nor the size of race differences in IQ are a matter
of dispute, only their cause," write the authors. The Black-White difference
has been found consistently from the time of the massive World War I Army
testing of 90 years ago to a massive study of over 6 million corporate,
military, and higher-education test-takers in 2001.
"Race differences show up by 3 years of age, even after matching on maternal
education and other variables," said Rushton. "Therefore they cannot be due
to poor education since this has not yet begun to exert an effect. That's
why Jensen and I looked at the genetic hypothesis in detail. We examined 10
categories of evidence."
1.The Worldwide Pattern of IQ Scores. East Asians average higher on IQ tests
than Whites, both in the U. S. and in Asia, even though IQ tests were
developed for use in the Euro-American culture. Around the world, the
average IQ for East Asians centers around 106; for Whites, about 100; and
for Blacks about 85 in the U.S. and 70 in sub-Saharan Africa.
2.Race Differences are Most Pronounced on Tests that Best Measure the
General Intelligence Factor (g). Black-White differences, for example, are
larger on the Backward Digit Span test than on the less g loaded Forward
Digit Span test.
3.The Gene-Environment Architecture of IQ is the Same in all Races, and Race
Differences are Most Pronounced on More Heritable Abilities. Studies of
Black, White, and East Asian twins, for example, show the heritability of IQ
is 50% or higher in all races.
4.Brain Size Differences. Studies using magnetic resonance imaging (MRI)
find a correlation of brain size with IQ of about 0.40. Larger brains
contain more neurons and synapses and process information faster. Race
differences in brain size are present at birth. By adulthood, East Asians
average 1 cubic inch more cranial capacity than Whites who average 5 cubic
inches more than Blacks.
5.Trans-Racial Adoption Studies. Race differences in IQ remain following
adoption by White middle class parents. East Asians grow to average higher
IQs than Whites while Blacks score lower. The Minnesota Trans-Racial
Adoption Study followed children to age 17 and found race differences were
even greater than at age 7: White children, 106; Mixed-Race children, 99;
and Black children, 89.
6.Racial Admixture Studies. Black children with lighter skin, for example,
average higher IQ scores. In South Africa, the IQ of the mixed-race "Colored
" population averages 85, intermediate to the African 70 and White 100.
7.IQ Scores of Blacks and Whites Regress toward the Averages of Their Race.
Parents pass on only some exceptional genes to offspring so parents with
very high IQs tend to have more average children. Black and White children
with parents of IQ 115 move to different averages--Blacks toward 85 and
Whites to 100.
8.Race Differences in Other "Life-History" Traits. East Asians and Blacks
consistently fall at two ends of a continuum with Whites intermediate on 60
measures of maturation, personality, reproduction, and social organization.
For example, Black children sit, crawl, walk, and put on their clothes
earlier than Whites or East Asians.
9.Race Differences and the Out-of-Africa theory of Human Origins. East Asian
-White-Black differences fit the theory that modern humans arose in Africa
about 100,000 years ago and expanded northward. During prolonged winters
there was evolutionary selection for higher IQ created by problems of
raising children, gathering and storing food, gaining shelter, and making
clothes.
10.Do Culture-Only Theories Explain the Data? Culture-only theories do not
explain the highly consistent pattern of race differences in IQ, especially
the East Asian data. No interventions such as ending segregation,
introducing school busing, or "Head Start" programs have reduced the gaps as
culture-only theory would predict. |
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