Of course, proponents of Herrnstein and Murray (see here for example) offer their own consistent arguments for these ideas. Supporting arguments seem to center around five points:

1. Accusations of Racism

2. Critics Misunderstand Intelligence

3. Intelligence and SES are Convoluted

4. Objective Evaluation of Intervention Efforts is Never Inappropriate

5. Other Supporting Evidence

6. Confusion of Scientific Results with Policy Making

1) Accusations of Racism

The accusation of racism of the authors of any study (not just Herrnstein and Murray) is irrelevant. "Even in those cases in the past in which racist assumptions can indeed be demonstrated, the proof of the pudding remains in the eating, not in the beliefs of the chef" (Chabris, Since the Bell Curve, Commentary Magazine, 1998).

Well… Meta analysis of outcome research for types of therapy showed that there was a greater chance of a researcher reporting positive results for a theory if it was the theory the researcher followed. This may mean that the proponent of a theory is more likely to get positive results, or is just more likely to publish them. Thus, the beliefs of the chef may or may not flavor the soup, but they do determine whether or not it gets served.

2) Critics Misunderstand Intelligence

Chabris notes that critics of The Bell Curve are attacking the basic assumption of g which is strongly supported both in studies conducted in the US as well as around the world. Further, the black and white gains also show up in other countries. Intelligence is a stable characteristic of a person, and though a person's performance may change from one situation to the next, intelligence remains stable.

Well… First, a solution with g was not the only solution to the factor analysis Spearman began, so while the possibility of g is not debated, it isn't the only way to understand intelligence. Second, Sternberg would argue they are confusing intelligence with intelligent behavior. Inferring the first from the second is more complex that simple IQ scores, which are very socially determined. Sternberg argues that what we know to put on intelligence tests is culturally determined (think about how we know to ask about marriage licenses and child labor laws, the meaning of the words transparent and plagiarize, how a democracy and a monarchy or praise and punishment are alike… in order to assess intellectual functioning?).

Sternberg, remember, also said that after having intelligence, you have to have the opportunity to show it in behavior. He discusses his research in other countries, noting the poor facilities (one study was temporarily halted when the school collapsed) and conditions (113 degree heat in the shade), and asking whether or not results obtained in these circumstances is really predictive of performance under good conditions. He writes about studies done in Morocco showing natives had better visual-analytic memory for patterns in rugs than Americans, likely because that's what they see in daily life. He found that children in Kenya showed a negative correlation between knowledge of the medicinal properties of native plants and scores on Raven Progressive Matrices. He explains this to stem from parents' goals and their children's abilities. Those who know the local fauna do so because they need to (95% suffer from parasites), and will likely grow up to be farmers. Those who can not learn the local practical knowledge as well invest their energies into doing well in Western-style school instead.

As a result, the WAIS IQ scores we see in people from the US versus another country are not comparable. Thus, international studies may mean little.

3) Intelligence and SES are Convoluted

Murray, in response to some of the challenges to the book, argues that those who attack his work on the grounds that IQ and SES were too convoluted should try coming up with some measure of SES that is not so convoluted.

Well… He has a point there I think. IQ and SES are convoluted. Smarter people should be able to make more money and be more successful with their greater resources, and less successful people often are less intelligent. The real convolution is the confusion of IQ and intelligence, and that with money. For example, is a plumber who makes $20 an hour and doesn't have $100,000 of student loans smart or not? Sternberg points out that Bush's SAT score was 566, less than a standard deviation above the mean (500+100) so within the normal range, and he's president.

4) Objective Evaluation of Intervention Efforts is Never Inappropriate

Murray also offers that many of the programs to raise IQ and decrease poverty actually have no impact on IQ and increase poverty.

Well… maybe we should question our remedial education, special classes, and scholastic improvement efforts to see if they do work. Head Start programs that select children from disadvantaged homes, give them some advantages for two years, and then return them to the same impoverished environment does sound silly. However, as discussed below, their review of the data on intervention programs was not very thorough.

5) Other Supporting Evidence

Jensen (2005) cites a large number of studies in a variety of areas to back up the hereditarian view. Jensen reports that results of racial differences on "pure g" or more culture-fair tests are stronger, and that this holds us in studies done in the US as well as other countries support this. He reports that African Americans have smaller brains, with brain capacity being strongly correlated with IQ scores as far back as the 1930s and 1940s.

Jensen (2005) cites studies of "racial admixture," or the percentage of European ancestry as determined by self-report or markers in the blood, that show more European ancestry is associated with higher IQs. However, Nisbett (2005) cites studies dating back to the 1930's that did not support this.

Jensen (2005) also cites studies exploring the genetic underpinnings of intelligence. He notes one study found that inbreeding in Japanese people (children from the mating of close cousins) correlated .48 with depressed IQ scores. He states, "We know of no nongenetic explanation for the relation between inbreeding depression scores from Japan and Black-White group differences in the United States" (page 251, 2005). This begs the question, while he does not know of any nongenetic reasons, does he know of any genetic ones? Suppose that people who suffer left-hemisphere strokes show a significant depression in their English fluency. Does that mean that English fluency differences between people on the West Side and the North Side of Chicago are due to strokes? Or does this mean that African Americans are inbred?

Jensen (2005) notes adoption studies have supported that black children in America, even after being adopted into white homes, still have lower IQs than their white adopted peers. Some of the twin study data seems to be like the inbreeding depression data. Jensen reports a study that showed monozygotic twins (with identical DNA) even when raised apart showed correlations in adult IQ of .49. Unrelated adults, even when raised together, showed a correlation of .01, or no correlation. So… what does this tell us about IQ differences? Imagine I do a study investigating the relationship between income and having nice furniture. I might find:

• people with lots of money who have lots of nice furniture, and I get a strong positive correlation supporting a connection

• people with lots of money and no nice furniture, which does not disprove a connection, but it doesn't show one either (maybe they don't want lots of furniture or have no taste)

• people with no money but lots of nice furniture, which does not disprove a connection, but it doesn't show one either (maybe they inherited it, or spent all their money on it)

• people with no money and no nice furniture, which doesn't allow me to make any conclusions, since income and furniture could be unrelated, or could be related very strongly, but not having found anyone with income I can't demonstrate any relationship

Now, lets extrapolate from IQ scores of twins with the same genes and unrelated people with different genes to the IQ scores of blacks and whites. I might find:

• blacks and whites are very genetically similar and have very similar IQ scores, supporting a relationship between genes and IQ (results did not support this according to Jensen)

• blacks and whites are very dissimilar in their genes but very similar in IQ (Jensen would argue the first is true but not the second), which wouldn't prove anything

• blacks and whites are very similar in genes and very dissimilar in their IQ scores (Jensen would argue the first is not true but the second is), which wouldn't prove anything

• blacks and whites are not similar in their genes and are not similar in their IQ scores (this is what Jensen holds as true)

However, using our example above of income and nice furniture, this last situation is the one in which we can't make any conclusions?

6) Confusion of Scientific Results with Policy Making

Gottfredson (2005) says that much of the fervor over this debate is because people think that showing a genetic difference between two groups will lead to discriminatory policies. She notes that genetic differences do not indicate any policy making decisions, and could neither support nor discourage equal rights or affirmative actions or laws.

However, Jenkins (2005) makes the case that in some cases, discrimination in hiring for example could be tenable since differential hiring could be based on genes, and on the best genetic qualifications for some jobs. And honestly, I think he hit the nail on the head for this issue; slippery slopes don't start out being slippery. They only get slippery after you take a few steps down.