[This is in reply to epoh (#122832, today at 07:47 AM). Apologies to all for the length, but I think the role of evidence here is extremely important.]
It will help if we get clear on the claims we're arguing about.
Claim 1: Genetics has a strong influence on intelligence. I have not heard anyone here dispute this.
Claim 2: All other things equal, smart people will tend to be more upwardly mobile than less smart people. This also seems fairly uncontroversial. What is being disputed is how much influence this actually has in sorting people into socio-economic levels.
Claim 3: Factors that have nothing to do with a person's innate intelligence can exert a strong influence on the adult phenotype, resulting in people with low coping skills who will remain poor. This can occur even in people who might have a genetic predisposition to high intelligence. This is the claim I am making, and that you seem to be disagreeing with.
Okay, now let's look at the evidence.
Your first two sources are popularizations. If there are particular peer-reviewed studies cited in those books that you think speak to your claims, I'd be happy to take a look at them.
Your third source merely addresses Claim 1, which is not at issue here.
Your fourth source primarily shows that a chaotic family environment negatively affects school performance, which supports Claim 3. (It also has a secondary finding that there is a genetic predisposition that makes some people more vulnerable to that chaos.)
I'm not seeing any evidence in these sources for your claims that "it's not due to early access to pre-school, it's not due to race, it's not due to time spent reading with small children, or other 'early literacy' activities. All of those things have been show to have very limited impact on a child's education."
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Now it's my turn. Evidence for Claim 3 includes the following. (I'm not going to do dig out all my references this evening, but please just ask if you'd like to see sources on any of these.)
- One of the strongest predictors of vocabulary in children is the complexity of the vocabulary that is addressed to them by adults before they reach school age. Unsurprisingly, that complexity of vocabulary of the adults varies dramatically by socio-economic status.
- Children who are expected by the teacher to improve a lot actually end up improving a lot, even when the teacher's expectations were experimentally manipulated (i.e. the experimenters lied to the teachers). And children they expect to stagnate end up stagnating.
- Racial stereotypes influence teachers' expectations of children. Stereotypes about SES influences teachers' expectations of children. (Don't think that's true? Just look at this thread.)
- There is a phenomenon called stereotype threat, where if you draw attention to a particular stereotype (women aren't good at math, black kids aren't good at academics, old people have poor memory), members of that group actually start performing worse than they otherwise would. Members of certain groups spend their whole lives being subtly and not so subtly disadvantaged by this phenomenon.
- Good nutrition in childhood not only affects body development, but also brain development. Even without actual food insecurity (which is more common that you might think) poorer children get poorer nutrition. Poor families often live in "food deserts," urban areas where there are no decent grocery stores for miles.
- Chronic stress has long-lasting negative effects on the brain.
- Serious levels of poverty are widespread in the United States. And yes, these are extremely stressful circumstances to grow up in.
- Less extreme poverty also has its hidden stressors. A family may have two cars (junkers, inherited from family members) that are neccessary to get the parents to their jobs, a cheapo pre-paid cell phone so they can contact their latchkey kids in case of emergency, and still get their electricity turned off on a regular basis because there's not enough money for the bills, and be one medical emergency away from bankruptcy.
(I hope I wouldn't need to provide evidence that school quality varies strongly by SES, or that low SES kids are more likely to be exposed to alcohol or drugs in utero, or that alcohol and drug exposure damages the developing brain, or that schools in poor neighborhoods have more violence which creates more stress.)
In short: smart genotype plus developmental disadvantages equals less-smart phenotype. Thus, smart genotype people may well remain in poverty generation after generation.
