The latest IQ study

The latest IQ study (below) has a slightly defensive air.  Despite ferocious efforts by Leftists to suppress findings that pop the bubble of Leftist claims, it seems that the genetic contribution to IQ has now become well-known and generally accepted.  So the effort nowadays seems to have moved towards proving that there are environmental influences too.  Previous IQ researchers have never doubted that and usually estimate that around one third of IQ is determined by environmental factors.

And the conclusions below disturb nothing.  Both genetic and environmental influences on IQ were found.  The main interest of the findings in this study therefore is *how much* influence  environment had.  The researchers report that a wealthy childhood environment gave the kid an extra 4 points of IQ -- about a quarter of a standard deviation -- over a kid brought up in a poor family.

If anything, that figure is perhaps a bit low. But the study is not a strong one anyhow.  It used adopted full-brothers rather than twins so genetic differences could be only roughly controlled for.  And assessing IQ in the late teens is not optimal either.  The influence of genetics is not fully revealed until about age 30  -- after the influence of early environmental factors has largely worn off.

Family environment and the malleability of cognitive ability: A Swedish national home-reared and adopted-away cosibling control study

By Kenneth S. Kendler et al.

Significance

Individual differences in cognitive ability result from a complex admixture of genetic and environmental influences. Adopted children are one way to estimate the degree of malleability of cognitive ability in response to environmental change in the context of a scientific design that can control for genetic differences among individuals. Sibling pairs in which one member is adopted away and the other reared by biological parents are a particularly powerful research design. In a large population-based sample of separated siblings from Sweden, we demonstrate that adoption into improved socioeconomic circumstances is associated with a significant advantage in IQ at age 18. We replicate the finding in a parallel sample of half-siblings.

Abstract

Cognitive ability strongly aggregates in families, and prior twin and adoption studies have suggested that this is the result of both genetic and environmental factors. In this study, we used a powerful design—home-reared and adopted-away cosibling controls—to investigate the role of the rearing environment in cognitive ability. We identified, from a complete national Swedish sample of male–male siblings, 436 full-sibships in which at least one member was reared by one or more biological parents and the other by adoptive parents. IQ was measured at age 18–20 as part of the Swedish military service conscription examination. Parental educational level was rated on a 5-point scale. Controlling for clustering of offspring within biological families, the adopted siblings had an IQ 4.41 (SE = 0.75) points higher than their nonadopted siblings. Each additional unit of rearing parental education was associated with 1.71 (SE = 0.44) units of IQ. We replicated these results in 2,341 male–male half-sibships, in which, controlling for clustering within families, adoption was associated with a gain of IQ of 3.18 (SE = 0.34) points. Each additional unit of rearing parental education was associated with 1.94 (SE = 0.18) IQ units. Using full- and half-sibling sets matched for genetic background, we found replicated evidence that (i) rearing environment affects IQ measured in late adolescence, and (ii) a portion of the IQ of adopted siblings could be explained by the educational level of their adoptive parents.

 SOURCE

Interesting that one of the co-authors above is Eric Turkheimer. Turkheimer is much loved on the left for  his demonstration -- using a group of poor 7-year olds -- that genetics is not an important determinant of IQ among poor kids -- where "poor kids" is probably rightly interpreted to mean "blacks".


Turkheimer

 What he found was probably little more than a restriction of range effect but he has repeatedly refused to release his raw data so we may never know.  Refusing to release raw data is a breach of all scientific protocols. We see it in Warmist researchers too.  It is pretty close to an admission of fraud.

The reason Leftists hate IQ tests is that they contradict the Leftist "equality" creed.  The application of that creed to blacks is however relatively recent.  Introductory psychology textbooks in the early '60s presented the black IQ findings without hesitation.  I remember it well. It was presented as one of the accepted findings in psychology.  As the great fantasy revolution of the '60s rolled on however, fact came to be replaced by righteous indignation.  The fantasists said that blacks COULD NOT be less intelligent so therefore the tests were bunk.

Equality has always been a silly but seductive dream.  It goes at least as far back as the "Levellers" of Cromwell's time.  And the Cromwellian era was undoubtedly much loved among America's founding fathers.  So Jefferson's "created equal" phrase in the Declaration of Independence is no surprise. But it is a pretty foggy phrase.  Are there many acts of creation or is normal childbirth an act of creation?  Or is it meant that God created Adam in such a way that all his descendants would be equal?  If so "The Fall" has clearly disrupted that intention.

But we should not take that part of the Declaration too seriously, however. The Declaration, like most political documents, was a product of much debate and compromise so Jefferson's ambiguous  phrase was just a device to keep  happy both those with Leveller beliefs and those with more realistic beliefs.

However you look at it, however, equality is a faith-based belief, not a fact.  It has no basis in fact.  Rejection of IQ tests is therefore a faith-based act. And the low average IQ scores of blacks are in fact powerful validation of the tests as measures of intelligence.

From the test results we would hypothesize that blacks would be at the bottom of just about every heap  -- and they are -- in income, education, status, health, lifespan and crime-incidence etc. What we know of black behaviour is powerful PROOF that the tests get it right.  Leftists can only reject the tests by closing their eyes to black behaviour. But they are very good at that

Posted by John J. Ray (M.A.; Ph.D.).