Achievement test gaps between children of less-educated and more-educated mothers are largely in place by age 3. That does not prove the gaps are largely genetic, but it is suggestive.
Actually I think that a gap by age 3 is suggestive of environment. Remember that adoptive children's IQs follow their adoptive moms until they leave home. I saw huge differences in how I interacted with my son from birth to 3 just within my small local circle. Compared to how I treated my son, the other moms basically treated their kids like loaves of bread. Cute loaves that were very kissable, but...well, you get the picture. Of course, my son may have been more reinforcing of my interactive behavior than other toddlers. And as the children grew, I saw that they had certian advantages that my son didn't have - for example, they were excellent at waiting around, while my son had a rather short fuse for it, even though my son was in day care 20 hours a week since 7 weeks of age and did plenty of waiting there. You should have seen the pictures they took of him with sad, saucer-like eyes staring off vacantly into space. "Look that this adorable picture we took of your adorable boy, Mrs. Grinity!" ((shudder))
Sorry that I have no point here - just to say that I think both Genetics and Environment (including prenatal) have an effect on IQ in ways that are both obvious and subtle. Breastfeeding, for example, does increase IQ
IF the child has a varient of genetics that allows BF to increase IQ. Chronic stress probably feeds back to the genome and turns off certian genes for 'relaxed exploration of the environment' that would normally be on.
One can think of lots of things that would prevent a child from reaching the upper level of their genetic potential range. Certian genes probaly protect one from particular environmental challenges. Isn't the whole complicated ball of wax amazing?
My guess is that all the current research is flawed in that so few people understand that for a positive reinforcer to be potent, it has to be potent
to that particular individual. So putting a child in an 'enriched environment' and measuring that it didn't help is only strong evidence if the particular enrichments actually did provide positive reinforcement to that particular child. Not only positive, but more strongly positive than the other reinforcers in the environment.
Smiles,
Grinity
