Nature via Nurture is a nice expression, and I seem to remember a study that talked about kids who are adopted getting an increase in IQ score by being raised by high IQ moms, but that as the children aged into young adults their IQ scores started to more resemble their birth parents. A difference of about 5 points sticks in my mind, but I can't remember if that was the original difference or what was left by young adulthood.
...and this brings up the interesting question (maybe the original question) of which measurement is more accurate: the one taken during childhood or the lower score as an adult? If one leans toward the belief that you can nurture a child into developing to his full potential such that his highest IQ score ever is the most accurate, but not the opposite: that you can nurture a child into performing beyond his true ability on an IQ test early in childhood, then the adoption studies would show more that nurture is the most important piece. The adult IQ numbers would be discarded as less accurate or due to deflation caused by lack of use into adulthood.
Then again, I'm not sure why adopted kids would show this pattern (and be more inclined to atrophy their brains over time due to lack of use) than would children raised by their birth parents.
