March 30, 2003
Continuing the IQ debate
Some comments on a reply by Unadorned on a previous entry.
This doesn't follow. The IQ studies in question have shown that variation in "environmental factors" (a term which merely means "all factors aside from genetic ones") cannot amount to more than a twenty-percent-to-fifty-percent influence on IQ.
That is incorrect. THe IQ studies have shown that the effect that environmental factors have currently is at most x%, but they have not shown that x% is an upper limit on their potential effect.
Let's give a simplified example. Suppose that there are three ways to raise a child, a GOOD, a COMMON, and a BAD way. An identical genotype, exposed to the GOOD influence will have an IQ of x+10; to the COMMON x; to the bad, of x-10.
Also, assume that the genotype, which controls the level "x" is normally distributed, say with mean 100. Now, in this setup, by examining a population who is subjected to the GOOD/COMMON/BAD way, we can quickly determine that there are hard limits to how much we can raise or diminish the population mean. I.e., we cannot raise it above 110, or diminish it below 90.
But, if tomorrow the GOOD way of upbringing is abandoned, then the mean IQ may only be made to range between 90 and 100. Conversely, if an EXCELLENT way of upbringing is discovered which confers an advantage of +30, then the population could acquire a mean IQ as high as 130, e.g., if everyone starts raising their children in the EXCELLENT way.
Thus, I stress that the x% genetic refers always to a given genetic/cultural situation, and says absolutely nothing about the potential that nurture may have on IQ in the future inasmuch as it cannot quantify the effect on IQ of currently unknown cultural practices.
This is a bold statement. Nothing said above disproves the contrary assumption that the results of the IQ studies in question apply to people in general, not just to the testing subjects' particular races or nationalities to the exclusion of other races and nationalities.
Indeed, my statement is correct. To see why this is the case, imagine a population that has extremely low genetic variability (in the limit: zero genetic variability - identical twins). In that case, most of the observed variability (in the limit: all) will be due to environment.
Conversely, imagine an Orwellian scenario in which every individual is subjected to exactly the same set of influences. In that case, the environmental variability is zero, and all the observed variability will be due to genes.
There is no reason to think the twin studies and other research which form the basis for the proof of the heritability of IQ don't apply to races/nationalities (or whatever) other than those of the people who were actually studied.
I have explained above why in fact one cannot generalize from a given population group to other population groups.