-It has to establish that these are fixed genetic, heritable differences, rather than anything else.
Murray's core arguments and the implications he draws do not depend upon genetic determinism.
No, but they do depend on these factors being beyond manipulation by other means, a point he himself makes.
All that needs to be assumed is that factors outside of direct control combine to impact early brain development in a manner that creates relatively stable differences in various cognitive abilities that have an impact on cognitive performance (either directly and/or via effects upon rates of learning from practice and experience). If, the causes of these developmental differences were factors impacting fetal development, how exactly would that change his arguments?
It would demolish them entirely. If it all turned out to be based on external factors influencing fetal development then his call to reform society would entirely spurious - all we'd need to do is adopt best practice in early stage pregnancy and the entire problem disappears.
-It has to establish that IQ is a measure of inherent ability or potential.
IT only has to establish that there are measures showing relative stability in a related basic cognitive processes that impact performance and rates of improvement in performance across many intellectual tasks, such as reading comprehension, logical reasoning, arithmetic, scientific argumentation, etc..
Not so. There are plenty of existing factors that already have these characteristics. Parental income, for example. Parental income is relatively stable, and relates to basic cognitive processes that impact performance. It's also highly heritable. But there's no logic to the idea that we should structure society around family wealth.
No, his ideas depend on IQ being inherent to the individual - otherwise his social ideas become a nonsense.
-It has to establish that these differences are meaningful on a practical level
With the number of intellectual tasks that the g-factor predicts performance on, the only way it is not practically meaningful is if essentially all of formals education (which seeks to develop skills on these very tasks) has no practical meaning.
Again not true. IQ could be the result of formal education, rather than a predictor of it, thus making it meaningless on a practical level, while formal education remains important.
Even then, IQ test still have meaning in determining success within formal education and thus upon everything that is in turn impacted by one's schooling, both in terms of grades, graduation, college attendance, degree type, etc..
'Determining'? Careful, you're in danger of assuming causation from a finding of correlation - a fairly critical statistical error. IQ is correlated with academic success. That doesn't mean it causes or determines it.
Togo said:
But the biggest gap by far is in the area of demonstrating that these values represent a practical difference. Gould's criticisms are the most famous, mainly because he goes into the most detail. It boils down to:
-The differences being described between groups are very small.
-The individual differences between people in the groups are extremely large.
In nearly every behavioral or medical experiment the group differences are a fraction of the individual differences among people within a group. This does nothing to undermine inferences about the contributors to the differences.
No, but it does undermine the social recommendations that Murray is making, since they depend not on group differences, but on individual performance. Which is not significantly effected by membership of the group. What he's doing is measuring a group difference, assuming this implies an effect on the individual, and then recommending social change to cater for these individual differences that he has not managed to measure. It makes a sort of naive sense, but statistically it is nonsense. If he could detect his group membership factors being significant predictors of individual performance, he wouldn't need group differences.
In addition, if biology were the cause of general intelligence, then even if those biological factors had some relation to race, one would still expect larger within group differences in IQ than between group differences. This is because the difference in the biological factors will almost always be greater between the most extremely different members of a single group, then between the most prototypical and statistically "central" members of different groups. Nothing about this in any way undermines the central points of that book.
It undermines his recommendation that society be restructured to cater for differences in IQ. It also undermines his discussion of how various groups within US society have fared as being driven by IQ. It further undermines his contention that the increasingly unequal nature of US society is a result of employment increasingly relying on cognitive processes.
It pretty much sinks the whole thing. You can probably rescue g as a concept, but that's not what the book is about.
-The authors, intentionally or otherwise, blur the differences between differences between groups and differences within groups.
Yes, because the issue is not merely group level differences but individual differences that can sometimes manifest as differences at the group level if the factors that determine the differences are partially related to the factors that define group membership. The group differences are not the point. They are used just as an illustration and because most people (especially critics of his books) view society entirely in terms of groups and their different outcomes rather than variance at the individual level. Most of their critiques and those who focus everything on race care only about making the aggregate outcomes between groups the same by any means neccessary, no matter what injustices must be done at the individual level. To them, it does not matter whether an individual white person actually got advantages over an individual black person. All that matters is that giving special treatment to the black person over the white (even if the black person already had more advantages) will make the group level aggregate outcomes more equal. The Bell Curve authors do not see group level unequal outcomes as the sole problem to be addressed, and refer to them in service of a larger point about individual differences.
If he could detect individual differences based on group membership, as distinct from other factors that Murray claims don't properly manipulate IQ, why didn't he publish them?
