The old IQ comparison studies that looked merely at skull size or head circumference as proxies for brain size, have been superceded by more advanced brain imaging capable of precise measurements of whole brain, total grey matter, total white matter, specific brain centers, and specific brain pathways and networks. These volumes are, to a large extent, under genetic control. A new era in comparing group IQs is dawning, thanks to advanced brain imaging and matching analysis of brain genetics. And a new era in improving gene expression relating to cognition is near to dawning -- as long as the key research is carried out and not obstructed out of a misguided sense of "political correctness."
Brain size as measured by MRI correlates highly with IQ. Specific brain networks and brain centers are even more highly correlated to IQ than gross brain size. In fact, a particular type of MRI analysis -- diffusion tensor imaging -- may supersede traditional IQ tests as the most objective means of testing IQ.
Anyone who truly wants to get to the bottom of the question of IQ differences between population groupings, will want to see the best designed, executed, and analysed research possible done on the subject. Anyone who is afraid of having such research done, does not truly want the question answered, and is lying to himself and everyone else when he claims that "there are no IQ differences, and even if there were it wouldn't matter!" Such persons' voices should be ignored as mere noise by all of those committed to finding the best answers to important questions.
A recent UK study at UCL Institute of Child Health, finds that teens who were delivered premature at birth have significantly lower brain white matter and IQ. (Abstract Annals of Neurology) For this study, it would be helpful to match by ethnicity, sex, and SES.
Between species, a longer gestation and breast feeding, correlate with larger brains, higher cognition, and longer lifespan.
And on and on. As brain genetic expression is correlated with advanced brain imaging with greater precision, and further correlated with IQ (and executive function), the larger global picture of human brain development should become clearer. At that point it will be impossible to deny the glaringly obvious group differences in brain function, and how these differences manifest themselves on a societal and economic level.
Being an HBD (human biodiversity) denier is growing more untenable every day.
Previously posted at Al Fin blog.