I wonder if early childhood nutrition has ever been looked into as the reason for the discrepancy in IQ between groups. I think that and exposure to complex language as early as possible might be large factors,(reply>), Of course it’s been looked into. We KNOW it isn’t why some groups have an average 1 standard deviation below others (blacks vs whites) or above others (Ashkenazi Jews vs other whites).,(reply>), ​@phantomcreamer I broadly agree that the data from twin studies rules out most environmental factors as a systemic influence on individual IQ differences (hence the hunt for elusive X-factors), but I should mention that most twin studies do not involve adoption, and in cases where they do, the adoptee households tend to be middle-to-upper class.  So the differences in environment aren't usually 'enormous', they just... don't seem to make much difference to most traits.<br><br>However, looking at the children of lottery winners does give you a reasonable idea of what happens to kids from poorer backgrounds (by OECD standards) who suddenly get a huge boost in SES.  (There are moderate benefits to health outcomes, but none when it comes to skill development, reading level, et cetera.)<br><br>With that said, I recall at least one paper summarising a big multiracial sample set from Sweden- I think the title of the article was The Wonders of International Adoption, by Bryan Caplan, if you want to search for it- that did indicate significant (up to 7-point) IQ gains for <i>international</i> adopted kids from poorer nations.  So nutrition and literacy and so on do probably matter at the global level, it's just those variables are mostly maxxed out in richer nations.<br><br>One final point I'd make, aside from pointing out the Flynn Effect exists, is that Flynn Effect gains seem to have been most concentrated in the lower half of the IQ distribution.  The cognitively poor seem to have gained more than the cognitively blessed.  (These effects would be invisible to twin studies or anything else looking at age-matched peers because they do comparisons within the same generation, rather than across generations.  Unfortunately, for pretty similar reasons, we have no real idea what causes the Flynn Effect.),(reply>), ​@Son of Soweto I didn't say that high-performing African migrants disprove the genetic hypothesis so much as that they complicate it.  (The data on lack of RttM among nigerians etc. is also relatively sparse, but then this whole topic is badly under-researched.)  Occam's razor applies, and all that, but it's not like cultural and environmental explanations don't get pretty ad hoc in their own ways.<br><br>The policy goal of focusing on intensive early childhood interventions to try and ameliorate racial IQ gaps has been in vogue since at least the 1960s- Jensen got in hot water for reporting on how these were... overhyped... way back in '69, which I think Haier mentioned in the interview.  The reason why woke radicalism is peaking among modern millennials is not because these programs haven't been attempted, but because they were attempted exhaustively and failed to security parity of outcomes, for decades.<br><br>(To be clear, programs like Head Start did actually have noticeable benefits when targeted at high-risk kids, in terms of reducing long-term risks of crime, drug use, divorce and unemployment.  They just had no long-term impact on IQ scores.),(reply>), @phantomcreamer maybe we need to really define what is it that iq measures, I contend that it measures human intelligence, which is reasoning and problem-solving abilities. If we agree that this is the case than my argument is solid.,(reply>), @Son of Soweto You're missing the point. The IQs are the "same". So, your hypothesis is demonstrably false.