3) Misinterpretation of the Studies

• First,Herrnstein and Murray forget that IQ is not a perfect measurement of intelligence, and even if it was, there would still be some error associated with our measurement of it. Of course, Gardner, Sternberg, and others have been arguing this for years, and that even if intelligence tests were very very good at assessing what they measured, there would still be quite a bit more about intelligence they didn't include. Thus, even if people show real differences in IQ scores, it is an unsupported leap to assume they show differences in intelligence.

• Even if IQ and intelligence are the same thing, and 60% of intelligence is attributable to genes (which many say is an overestimate), that still leaves at least 40% of intelligence that is not genetic, or that is environmentally determined (which might be an underestimate if remember that c² and h² may overlap). Flynn (1999) notes numerous studies that show direct evidence of environmental effects on intelligence, and points out that 40% is still a lot of variability they don't account for. Thus, it is an unsupported leap to say genes are the main thing we should be concerned with.

Sternberg recalls that a century ago, the average IQ of immigrant Italians was 87. Respected scientists discussed this at length, recommending mass IQ testing for all immigrants. Goddard said most Italians were "feeble minded" as well 80% of Russian and Hungarian immigrants. Today, the average Italian-American IQ is just above 100. Four or five generations of breeding with Americans should not be able to produce such a positive genetic effect if genes are all that matter.

Sternberg also points out that Herrnstein and Murray review studies that show that among blacks and whites of the same IQ, blacks were twice as likely to be born premature and to live in poverty during the first three years of life, and three times more likely to be on welfare. Thus, clearly something was impacting their station in life besides intelligence.

• Even if IQ and intelligence are the same thing, and IQ is primarily determined by genes, Gardner says it is tricky to link genes and IQ, then IQ and social status, and thus genes and social status. Herrnstein and Murray note that their reported correlations between IQ and social status are around .44. This would mean IQ explains 20% of the variance (.44²) in social niche, and that genes explain 20% of the variance in social niche only if IQ is 100% determined by genes. However, the heritability estimates Herrnstein and Murray give are that about 60% of IQ is genetically determined. Thus, 60% of 20% is 12%, or the degree to which your social niche is determined by the genes that determine IQ. Thus, the leap to conclude that social status tells us anything about genes is unsupported.

• Gardner (1995) says Herrnstein and Murray make faulty links between crime and IQ, assuming that both are steady when data indicates this is not so, and ignoring "white collar crime" (I promise, Enron executives and Martha Stewart are not low IQ people).

Sternberg (2005), in reply to the dangers associated with low IQ for our society, makes a point too about the dangers of high IQ. Thus, Sternberg says, we should be thoughtful about what level of IQ really leads to harm in our country. He says that high IQ is correlated with:

• making bombs

• making and distributing anthrax in a form as a weapon

• terrorist attack plans that include successfully evading capture

• getting shot in regime changes (Stalin first shot all the intellectuals when he came to power)

• The differences between "White" and "Black" people they note show up between many subgroups of "White" people and disappear over time as well (Sowell). Given this, you either can not lump "white people" into a group together because of the genetic differences that must exist between them (according to Herrnstein and Murray) to explain IQ gaps. Alternately, you can lump them all together, but you have to offer another factor that could explain IQ gaps besides genetics.

  
  

• Herrnstein and Murray in their review of the heritability data fail to note that heritability studies with twins show that heritability estimates for IQ are lower for low SES twins and higher for middle to upper SES twins. McLoyd argues that poverty has its greatest impact on cognitive development during the preschool years or younger, and so any period of poverty in a child's life may have lasting effects. Given that Herrnstein and Murray chose studies that used at-risk groups or minority and poor children (and this is most of what's out there), many of the interventions they review to raise IQ were working against an environmental force, which raises two questions

  1. in the presence of the defective genes Herrnstein and Murray note, and the presence of a defective environment, how do you determine the cause of the intervention's failure?

  2. if some reparative efforts have had little effect (which Herrnstein and Murray rightly note), what would have been the results of preventative efforts? We can't make any conclusions on this.

Turkheimer reviews five studies showing differential heritability estimates between whites and blacks. He analyzed data for over 48,000 mothers and their 59,000 children assessed as part of the National Collaborative Perinatal Project. He found that the heritability for genes and WISC scores in upper SES (mostly white) families was 72% and the environmental estimate was 15%. However, the heritability estimate for low SES (mostly very poor black) families was 10%, and the environmental estimate was 58%.

• Jensen (2005) cites Osborne as showing that heritability estimates for blacks and whites were equal, and so genes were equally important in determining both group's IQ scores. Osborne did a study in 1980 of 123 black and 304 white twins, and calculated heritability estimates from several tests. While the heritability estimates did average to 45-55% for whites and blacks, there was considerable variability. On the Cattell Culture Fair Intelligence Test, for example, heritability estimates for white twins was 71%, but for black twins was 19%.

This could still support a genetic interpretation though. Consider that being blind in a school with no accommodations could certainly impact your academic functioning. Suppose I require all my students to have an eye exam before classes begin, and I correlate visual acuity and GPA. I likely will get a zero or very small correlation. It's not that being blind does not impact your performance as we had anticipated; rather, it is that you likely have no visual problems (and no impairment in your GPA as a result of visual problems), or visual problems easily corrected by glasses (and no impairment in your GPA as a result of visual problems after you get glasses). In five years here I haven't had any blind students. Thus, blindness can't really impact the correlations because I wouldn't have any blind people in the study.

Now imagine that there are genes for stupidity (sorry, slower nerve conduction, less extensive arborization of neurons, decreased myelination of the axons, less effective metabolism of glucose in the brain…). Of course, these things make a difference in the functioning of the brain, but suppose that black people have very few of these defective (sorry, less desired) genes. Heritability estimates would be very low in blacks, since there would be very few less desired genes floating around to impact intelligence (like very few blind people to impact the correlations above). Suppose that whites, on the other hand, have considerably more of these less desired genes. Heritability estimates would be much higher for whites, since there would be a higher base rate of less desired genes that would be available to negatively impact intelligence. Funny… I haven't heard anyone mention this possibility in the debates….

• On twin and adoption studies… Scarr and Weinberg published their study in 1976 and followed adopted white and black children for 12 years. They found:

  • white children living with white biological parents had mean IQ scores of 109, GPAs of 3.0, and class ranking in high school of 64%tile

  • white children adopted by white parents had mean IQ scores of 106, GPAs of 2.8, and class ranking in high school of 54%tile

  • black children adopted by one black and one white parent had mean IQ scores of 99, GPAs of 2.2, and class ranking in high school of 40%tile

  • black children adopted by two black parents had mean IQ scores of 89, GPAs of 2.1, and class ranking in high school of 36%tile

  Tizard (1974) did a similar study and found:

  • black children adopted by white families had an average IQ of 117

  • black children adopted by black families had an average IQ of 104

  • black children not adopted at all had average IQs of 85

Nesbit asks why, if intelligence is mostly genetic, would adoption raise the average IQ for Tizard's children by 19 points? And adoption by white as opposed to black parents raise IQ by 13 points? Why would there be a 10 point difference in Scarr and Weinberg's IQs for children adopted by one versus two black parents? Willerman et al (1974) reviewed the data further and found a 9 point higher IQ on average in children if the mom was white versus if the mom was black. The only way that genes can explain these differences is if somebody else's genes impact your IQ. Obviously, something more than genetics comes into play (such as SES, community resources, and home stability) and this "something more" is enough to take care of most, if not all, of Herrnstein and Murray's noted differences between white and black IQs. If environmental changes can explain the gap, then how can you rely on genetic explanations?

4) Study Choice

• Herrnstein and Murray dismiss one study that was very unique. The researchers studied IQ in children of German women and American soldiers, some black, some white, after WWII. The white and black children did not score differently on IQ tests, which would support that "white" and "black" genes didn't seem to be any different as far as IQ. Further, the white-black racism seen in America isn't as prevalent there, so the environments for these children would have been much more similar.

  
  

• Gardner says Herrnstein and Murray ignore contradictory evidence, including that interventions to raise SAT and other types of test scores have worked, and that children raised in certain areas of the country and in certain types of homes have higher IQ's regardless of their ethnicity. Herrnstein and Murray note that verbal interactions between white parents and children are excellent preparation for IQ tests (meaning they do raise intelligence), but fail to consider that black parents engaging in the same dialogue with black children could raise their IQ's (meaning their intelligence) as well.

  
  

• Herrnstein and Murray's analysis of the impact of enrichment programs indicates they are ineffective; this analysis may be flawed, and IQ scores may be very amenable to change. In those studies that failed to show a difference:

  • in many cases the enrichment program ceased at a young age, and so follow-up evaluation and assessment was halted; actual achievement during teen and adult years could not be assessed in these cases

  • after the end of the enrichment program, the children in these studies were typically returned to the impoverished environment they were drawn from, which over time likely eroded the strength of the results and led to no results when follow-up was conducted

  • while IQ's of enriched children might not have proven to have been as high as other children at follow-up, there was often no way of knowing what they might have been since there was no suitable control group to compare them to

  • many of the studies used at-risk or MR children, making it difficult to generalize from them to "normal" children

  • there have also been studies of the effects upon children of heroin-dependent parents; research showed that it made no difference whether the mother or the father abused heroin (thus, the issue was not the heroin crossing the placenta, but the early neglect), and that there may be a "window of opportunity" to remove the child and place them in a non-neglecting home (so while some studies have failed to show successful effects, their implementation may have to be carefully timed)

  • pre-school enrichment programs may keep children in school longer; if years in school is correlated with IQ, then this in and of itself could have been an intervention benefit

However, not all studies failed:

• many studies did show good support for the efficacy of enrichment programs, in the infant, child, teen, and adult years

• there is plenty of data on SAT score and mathematics scores improvement in college populations

• adoption, while not an "intervention" to raise IQ per se, appears to do this. Flynn (1999) discusses Skodak and Skeels' study that found that there was a 20-point IQ gap between black biological mothers and their children adopted into white homes. This difference should be reduced after correcting for the differences in the tests used, but even after this a difference of 10 to 13 points remains. Since the genes between parent and child are more similar than for any group in the population at large, the differences were most likely environmental. Thus, an environmental change can impact IQ scores by almost a full standard deviation.

• Campbell and Ramey (1994) did a study training black infants in cognitive skills development, and matched them to a control group. At age 12

  • 56% of controls had IQs > 85, while 87% of participants did

  • 37% of controls had IQs <85, with 7% being in the MR range, while 13% of participants had IQs < 85, and none were diagnosed MR

  By age 15

  • 48% of controls had been placed in special education classes, while only 12% of participants had

  • 56% of controls had failed a grade, while only 30% of participants had

  Thus, not all efforts to raise IQ scores have failed miserably as Herrnstein and Murray seem to believe, and the ones that failed could have failed for a number of reasons other than genetics. So, even if IQ and intelligence are the same thing, and even if IQ is primarily determined by genes, and even if some aspects of social status are determined by genes, there's still plenty of evidence that other factors impact social status.