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The Bell Curve: Intelligence and Class Structure in American Life

Posted by StepTb su giugno 27, 2017

Free Press, 2010 (first published 1994)
912 pages
Authors: Charles Murray, Richard Herrnstein

It’s the most famous book by Murray, and most likely also his worst.
It must be noted that a lot of people attacked and still attack TBC without having really read it – the book is deeply flawed, but it’s not a racial eugenics manifesto, and doesn’t even focus on race.

The book was published only 4 years after the Human Genome Project started, but presented as definitive, established facts things that were not, and still aren’t. The authors, who are not genetists, misrepresented the state of genetics by taking simplistic stances and presenting them as if they were the scientific consensus.
Even worse, the book damaged the possibility of seriously debating biology-informed policymaking, by proposing policies based on that simplistic misrepresentation and not even really backed by the book’s own content.

The whole book flows from a catastrophically wrong assumption: that “heritability” means “genetic determination”.
This alone is enough to make TBC a pseudoscientific work.

There are also other fallacies. The authors are always careful enough to mention studies showing that the relationship between genetic components and environmental contributors is so complex that we basically don’t know how to separate them, and we don’t really know how and why IQ/ability does or doesn’t increase both inter-generationally and during the first 15 years of life, but then they go on with their conclusions as if those studies were irrelevant or not even mentioned a few pages earlier. In reality, most of the contradicting studies they quote, like the documented increase of 7 IQ points per decade in 18 year olds in The Netherlands and Belgium from the 1950s to the 1980s, are enough to falsify their conclusions.

More recent studies have even shown that IQ heritability itself is high among high socioeconomic status families, but significantly lower among low socioeconomic status families, thus showing TBC’s conclusions are not only the product of a false equivalence, but also of fallacious measures in the first place.
Which demonstrates how more research into heritability is especially important: to falsify pseudoscience that has a particularly dangerous potential.

So what’s there to save? The first chapters in particular, where the authors describe the phenomenon of social, economic and cognitive clustering in the American society, which wasn’t as clearly perceived as a problem in the 1990s as it is now (we’re only now, maybe, waking up to the nefarious effect on Western democracies of bubbles and polarization, combined with other issues). But TBC doesn’t analyze it the way it should (again, the authors like the simplistic and wrong explanation of “genetic determination” too much to do that), and Murray wrote another book in 2012 talking about the same process more at length.
Another interesting and important point is the steady decline in fertility of high-IQ women, but, again, it’s not really analyzed.
The heated debate stirred up by TBC also contributed to a widespread revision of the “blank slate” assumption, and underlined some negative externalities of some policymaking based on strict and fixed demographic categories.

More in-depth and very balanced reviews that I fully agree with, and that explain all the other problems with TBC way better than I possibly could:
http://www.nyu.edu/gsas/dept/philo/faculty/block/papers/Heritability.html
http://reason.com/archives/1995/03/01/cracked-bell/

Check the textbook Psychology, chapter “Intelligence”, for a correct overview of what science knows about it.
Check The History and Geography of Human Genes for a serious book about genetics and human differences.

4/10

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