This was yet another fascinating SH paper:
Apparently, causal biological-environmental effects do not tend to induce g-loaded effects. Quote:
The previous group comparisons concerned ethnic groups, and additionally we explored differences between subgroups within an e ethnic group. The analyses on subgroups that differ with regard to religious belief and the school type the subgroups attend, respectively, did not yield strong positive correlations, as is generally the case in comparisons between ethnic groups. In particular, differences in IQ between religious groups, namely Catholics, Protestants, and atheists, showed a correlation d x g of close to zero. Differences in IQ between school types showed a small correlation d x g. Therefore, subgroup differences do not seem to have a particularly strong relationship with g. These findings can be construed as providing support for the hypothesis that when comparing samples only group differences and generally not subgroup differences are strongly and positively related to g. However, it should be mentioned that te Nijenhuis et al. (2009) reported a rho = +1 for differences between gifted persons and average persons. Clearly, more exploratory meta-analyses are required to see which subgroup differences act like ethnic group differences. In previous studies, genetic variables were found to have a strong positive relationship with g. Therefore, we expected that also the heritability coefficients of reaction time measures would show a strong correlation with g loadings. A bare-bones meta- analysis on two studies revealed a correlation h² x g of .51. T his finding provides modest support for our hypothesis. A range of physical characteristics of the brain was found to have a substantial correlation with g . In the present study, we explored the relationship between brain volume and g. Results indicate a modest correlation d x g. Spitz (1987) hypothesized that biological-environmental variables mimic the pattern of genetic variables. Previous studies on this topic, however, did not indicate a pronounced relationship between the biological – environmental cocaine-, lead-, and smoke- exposure. Nonetheless, it was still possible to find support for Spitz’ hypothesis in studies of other biological – environmental variables. Therefore, we explored the correlation d x g of the variables iodine supplementation/ deficiency, prenatal cocaine exposure, fetal alcohol syndrome, air pollution, traumatic brain injury, and malnutrition. The picture that emerged from all this studies is straightforward: Differences in IQ caused by these biological – environmental variables are virtually unrelated to general intelligence. A further exploration of the psychological phenomena aging and autism revealed that IQ decline in aging has a substantial relationship with general intelligence, but the meta-analytical correlation is clearly not +1. The analyses showed that an analysis of gains on broad abilities is more likely to be helpful for understanding this phenomenon than the g factor. The IQ profile of autistic groups clearly does not correlate with general intelligence. [Emphasis added].
I had thought the same as Spitz and so now stand corrected. Hmmm…