(see "The Blank Slate")The book The Blank Slate was published almost a decade ago
http://www.amazon.com/Blank-Slate-Modern-Denial-Nature/dp/06...
and research has moved on. The chapter in The Blank Slate that has the most to do with heritability of cognitive abilities is largely based, as author Steven Pinker acknowledges in his bibliographic references, on the work of Eric Turkheimer. But Turkheimer has revised his point of view in the last decade, and if Pinker is still reading Turkheimer's writings, Pinker should too. I'll recommend here two articles from Turkheimer's faculty web page
http://people.virginia.edu/~ent3c/vita1_turkheimer.htm
that more readers of Pinker's book ought to know about, to bring their understanding of human behavioral genetics up to date.
Johnson, Wendy; Turkheimer, Eric; Gottesman, Irving I.; Bouchard Jr., Thomas (2009). Beyond Heritability: Twin Studies in Behavioral Research. Current Directions in Psychological Science, 18, 4, 217-220
http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O...
is an interesting paper that includes the statement "Moreover, even highly heritable traits can be strongly manipulated by the environment, so heritability has little if anything to do with controllability. For example, height is on the order of 90% heritable, yet North and South Koreans, who come from the same genetic background, presently differ in average height by a full 6 inches (Pak, 2004; Schwekendiek, 2008)."
Another interesting paper,
Turkheimer, E. (2008, Spring). A better way to use twins for developmental research. LIFE Newsletter, 2, 1-5
http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O...
admits the disappointment of behavioral genetics researchers.
"But back to the question: What does heritability mean? Almost everyone who has ever thought about heritability has reached a commonsense intuition about it: One way or another, heritability has to be some kind of index of how genetic a trait is. That intuition explains why so many thousands of heritability coefficients have been calculated over the years. Once the twin registries have been assembled, it’s easy and fun, like having a genoscope you can point at one trait after another to take a reading of how genetic things are. Height? Very genetic. Intelligence?
Pretty genetic. Schizophrenia? That looks pretty genetic too. Personality? Yep, that too. And over multiple studies and traits the heritabilities go up and down, providing the basis for nearly infinite Talmudic revisions of the grand theories of the heritability of things, perfect grist for the wheels of social science.
"Unfortunately, that fundamental intuition is wrong. Heritability isn’t an index of how genetic a trait is. A great deal of time has been wasted in the effort of measuring the heritability of traits in the false expectation that somehow the genetic nature of psychological phenomena would be revealed. There are many reasons for making this strong statement, but the most important of them harkens back to the description of heritability as an effect size. An effect size of the R2 family is a standardized estimate of the proportion of the variance in one variable that is reduced when another variable is held constant statistically. In this case it is an estimate of how much the variance of a trait would be reduced if everyone were genetically identical. With a
moment’s thought you can see that the answer to the question of how much variance would be reduced if everyone was genetically identical depends crucially on how genetically different everyone was in the first place."
I've enjoyed learning about this line of research from several well known behavioral geneticists, including some of the doyens of twin research, as I participate in the journal club in individual differences psychology and behavioral genetics
http://www.psych.umn.edu/courses/fall10/psy8935/default.htm
at the university where those researchers are based. There is always lively discussion on what the data show, and what the data don't show. Thus far, there are no data to show that poor people are poor solely because they lack academic ability (and anyway studies show
http://www.jkcf.org/assets/files/0000/0084/Achievement_Trap....
http://tcf.org/publications/pdfs/pb428/carnrose.pdf
http://reason.com/archives/2008/02/19/legacies-of-injustice
that poverty is a meaningful disadvantage even for high-ability young people).
Nor is there any predictable limit on how much poor people might be able to use their abilities, whatever their current ability level, to improve their condition in life if the undeniable disadvantages of lacking money were alleviated.