Turkenheimer: https://web.archive.org/web/20191231135901/http://pdfs.semanticscholar.org/4621/a1b603d5389e874aab00a60efa588140ccea.pdf https://web.archive.org/w

Turkenheimer: https://web.archive.org/web/20191231135901/http://pdfs.semanticscholar.org/4621/a1b603d5389e874aab00a60efa588140ccea.pdf https://web.archive.org/web/20191231135901/http://pdfs.seman... > Results demonstrate that the proportions of IQ variance attributable to genes and environment vary nonlinearly with SES. The models suggest that in impoverished families, 60% of the variance in IQ is accounted for by the shared environment, and the contribution of genes is close to zero; in affluent families, the result is almost exactly the reverse. [....] > In the low-SES group, the intraclass correlation was .63 for DZ twins and .68 for MZ twins, consistent with h2 of .10 and c2 of .58; for the high-SES group, the DZ twin correlation was .51 and the MZ twin correlation was .87, consistent with h2 of .72 and c2 of .15. [...] > In the fractious history of scientific investigations of the heritability of intelligence, the effects of poverty, and the relations between them, there has been only one contention with which everyone could agree: Additive models of linear and independent contributions of genes and environment to variation in intelligence cannot do justice to the complexity of the development of intelligence in children. Only recently have statistical models and computational capacity advanced to the point that less simplistic models can actually be fit. Although there is much that remains to be understood, our study and the ones that have preceded it have begun to converge on the hypothesis that the developmental forces at work in poor environments are qualitatively different from those at work in adequate ones. Clarification of the nature of these differences promises to be a fascinating, and hopefully unifying, subject for future investigation.