Edit to say the second paper is interesting, but it seems to me to have a number of flaws. If I understand this right, GWAS are capturing everything from the g

Edit to say the second paper is interesting, but it seems to me to have a number of flaws. If I understand this right, GWAS are capturing everything from the genome. This includes any genetic determination of appearance, food preferences, etc. Then the sample is only healthy twins from narrow genetic/cultural stock: England/Wales born over two years in the 90s. This means that in addition to sweeping up genetic factors associated with brain development, you are capturing all visible/inherent-behavioral inputs to a multi-stage developmental process that includes interactions with technology, other people, school systems, etc. Of course you can explain a majority of the outcome. It won’t replicate though, because it is dependent on that narrow time slice of culture, nutrition, parenting practices, technology, etc. If this study replicates in Asia, South America, or Africa, with similar genetic components in the PCA, I’ll admit I’m wrong. Heck if it even replicates in England with twins from the 1960s I’ll admit I’m wrong.