With all due respect to David (Hi!) I think a better reference is the following article published in 1915 and which provides some additional insights and cautions:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4749455/ aka: Turkheimer, E., Beam, C. E., & Davis, D. W. (2015). The Scarr-Rowe Interaction in Complete Seven-Year WISC Data From Louisville Twin Study: Preliminary Report. *Behavior Genetics*, *45*(6), 635–639. http://doi.org/10.1007/s10519-015-9760-4 One comment in this article from the discussion is relevant because Turkheimer's work has involved U.S. participants while the article I linked to (way down below) involves Europeans: " Whatever it is about the family or cultural environment that suppresses heritability in lower class families, it appears to be a factor that is more widely operative in the United States as opposed to Europe. Unequal access to education in the United States would appear to be a plausible explanation for the difference, but remains speculation awaiting detailed analysis." I wonder if this is another example of "American Exceptionalism"? ;-) Oh, and regarding the distribution of household income or, equivalently, SES, the authors of the above ref point out: " Descriptive statistics are given in Table 1 for the IQ scores and SES. IQ scores ranged from 46 to 143, with typical standard deviations close to fifteen. SES had a mean of 47 and a standard deviation of 26. The IQ scores were roughly normally distributed, as illustrated in Figure 1. ************ SES was more rectangularly distributed. ************ Parental SES was correlated .39, .39 and .29 with FSIQ, VIQ and PIQ, respectively. The relationship between FSIQ and SES is illustrated in Figure 2. Mother’s education ranged from seven to twenty years, with a mean of 13.2 years (SD=2.4). Father’s education ranged from six to twenty years, with a mean of 13.6 (SD=3.0). FSIQ was correlated .37 with mother’s education and . 39 with father’s education; mother’s and father’s education were correlated .72 with each other." So, though household income (and SES) might be highly skewewd in thee population (damned billionaires! I bet they never let their kids participate in these kinds of studies), it is best to examine the sample's distribution to determine whether skew is relevant (not likely in a rectangular distribution). The more relevant issue is what is the effect of correlation between two different distributions, namely between a normal and a rectangular distribution. The mismatch would reduce the ordinary Pearson r. One would need a correlation coefficient that is half Pearson (for the normal distribution) and half Spearman (for the rectangular distribution which ranks follow). But what do I know, right? ;-) -Mike Palij New York University [email protected] ----- Original Message ----- On Wed, 25 Jul 2018 17:02:10 -070, David E wrote The Scarr-Rowe interaction refers to heritability of IQ: very high at the upper end of the socioeconomic scale, very low at the lower end. You can see it in this paper, in Figure 3, for "A" (additive genetic variance) versus shared and unshared environment: <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.397.9014&rep=rep1&type=pdf> The usual interpretation is that people at the upper end of SES have the pleasure of being able to *express* their genetic differences in IQ, while those at the bottom do not. Seems like a natural fit for a study of the "heritability" of educational achievement. --David ----- Original Message ----- On Wed, 25 Jul 2018 19:43:27 -0400, Ken Steele wrote: Hi David: Please explain what a Scarr-Rowe interaction is and why it may be a rookie mistake not to take it into account. Your link summary/abstract does not clarify the issue. I fear that this discussion may be headed into a descending spiral where the label n@zi will be used. Best regards to all. Ken --------------------------------------------------------------------------------------------- On Jul 25, 2018, at 7:21 PM, David <[email protected] [3]> wrote: More troublingly, I'm not seeing any indication that they investigators accounted for a Scarr-Rowe interaction. Rookie mistake. That interaction should've been the *first* thing they looked for. Otherwise, as Eric Turkheimer has argued, they might be better off not estimating "heritability" at all <http://psycnet.apa.org/record/2011-18633-009 [4]>. --David Epstein [email protected] [5] ----- Original Message ----- Chris Green opined: Household income is incredibly highly skewed. Assuming they obliviously used a linear coefficient to obtain the 7% figure, it is probably a severe under-estimate of the true size of the effect. ………………………………... On Jul 25, 2018, at 1:58 PM, Michael Palij <[email protected] [10]> wrote: At least for White Europeans. A masive study using genomic info as a predictor of educational achievement showed that genes accounted for only about 11% of the difference in years of education. The Scientist Mag has a layperson friendly description of the study published in the journal "Nature Genetics". See:https://www.the-scientist.com/news-opinion/genes-explain-about-11-percent-of-differences-in-years-of-education-64552 [11] There are links in the article to additional sources. So, I guess this pretty much undermines "g" or single factor theories of intelligence (assuming intelligence drives educational achievement as certain theorists assert). In addition, household income accounts for only 7% of the variance in the differences which some might consider a unexpected low amount. I guess this all goes to show that your genetic ancestry (sorry Galton) nor wealth/poverty are the most important factors in academic acheivemnt, like getting a Ph.D. or other advanced degree. Now, I just hope the results are replicable. ;-) --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=52586 or send a blank email to leave-52586-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
