I am disappointed that Al has not responded. He stated that he knew of no scholarly work on IQ which did not recognize the difference between average black and white IQs.

I purposely misinterpreted his remarks to include an endorsement of the idea that this difference was due to genetic factos.

The left and right both make this misinterpretation routinely. The left proced to then attack the idea of the existence of IQ. The right generalize that IQ is almost entirely genetic and the difference must be racial, I.E. genetic.

Strictly speaking Al did not say anything about the genetic origins of the difference. Ergo, strictly speaking I did not really address what he said. I was trying to force him to make his position clearer with regards to either a genetic or environmental origin of the difference or the idea that no one at this point could say due to insufficient data.

Obviously, from the various posts in this forum, the question of the existence and nature of IQ is so politically charged that it is never discussed independent of race issues. Al's post was the first in this thread to raise that issue as I recall.

Jensen is the most famous advocate of the idea that the difference is genetic in origin. His argument runs.

Proposition: The difference in IQ between whites and blacks is quite significant.

Proposition: Such a significant or major difference could only be caused by significant or major environmental factors.

Observation: No such radical environmental features are present.

Conclusion: The difference must be genetic.

This is a very good argument. However, in order for it to be valid, the various points must be true. A difference of 15 points in average IQ must be so radical that only a radical difference in environment could account for it.
This requires a valid scientific knowledge of what is a radical environmental difference and what is a radical difference in IQ.

Neither of these exist. Jensen, and the authors of TBC base their conclusion on what might be called an intuitive belief about what these are. Now given the science of a few decades ago, and that when Jensen was young, this a very reasonable argument, and one which does not in any way suggest that Jensen is now or ever was a racist.

Now, if you look at feral children, you can see how radically the phenotype can be changed by truly radical differences in environment. Compared to these changes, a 15 point difference in IQ is almost microscopic. Relatively minor and can plausibly be induced by relatively minor differences in culture.

Second, IQ studies in Europe have shown an average difference between Polish and French of about 12 or 13 points. About the same as the difference between blacks and whites in the US.
Poles have the highest average IQ in Europe the French have the lowest, at least at the time the book I am referring to was written.

Apparently the cultural differences between Poland and France are sufficient to produce the level of IQ variation that exists between blacks and whites in the US.

The Flynn effect shows an incraese in raw scores on IQ tests over time a little more than 3 points every ten years. Apparently the cultural differences between one generation and the next are sufficient to produce a difference equal to that between whites and blacks in the US every 40 years or so.

It follows that based on available data of other equivalent differences in IQ between various groups, the difference in IQ between whites and blacks in terms of phenotypical variation is relatively small and can be easily explained as the result of relatively small differences between white and black culture.

Thus, Jensen's argument does not stand up when compared to data relating to other IQ differences between groups.

No one with serious credentials in Psychometry denies either the existence of the difference, or the existence of IQ. The arguments denying these two scientific facts originate entirely in political and dogmatic areas. There is real debate on whether the origin is genetic or environmental. Jensen is the acknowledged authority on the genetic side, Flynn is the acknowledge leader on the environmental side.

Flynn proposes a phenomenon he refers to as recipricol reinforcement. http://www.nathannewman.org/log/archives/000805.shtml

The URL above discusses the idea.