Scott Alexander responds to comments and criticism on his earlier post about 'Missing Heritability', discussing issues like gene-environment interactions, sequencing technology limitations, and the use of polygenic scores across ancestry groups. Longer summary

This post compiles and responds to notable comments on Scott's earlier post about 'Missing Heritability'. The post is structured in four sections, starting with responses from experts named in the original post, particularly Sasha Gusev who critiques the treatment of gene-environment interactions and cross-population polygenic scores. The second section features detailed technical comments from knowledgeable readers about topics like genetic interactions and sequencing technology limitations. The third section addresses specific corrections to the original post, while the final section covers various other interesting comments and discussions. Throughout, Scott engages with the criticisms and new perspectives while maintaining his original position on most key points. Shorter summary

Scott explores the 'missing heritability' problem in genetics, where twin studies show traits like IQ and educational attainment are highly heritable but newer genomic methods find much lower heritability, analyzing various potential explanations for this discrepancy. Longer summary

The post examines the 'missing heritability' problem in genetics, where twin studies consistently show behavioral traits like IQ and educational attainment are substantially heritable (around 40-60%), while newer genomic methods find much lower heritability (around 15-20%). Scott reviews the history of behavioral genetics research, explains various study methodologies and their potential biases, and analyzes different hypotheses for this discrepancy. He examines whether twin studies might be flawed, whether newer methods might be missing important genetic effects, and whether educational attainment might be an unusually problematic trait to study. While acknowledging remaining mysteries, he tentatively concludes that twin studies are probably largely correct and that newer methods may be missing rare variants and genetic interactions. Shorter summary

The post argues that 'non-shared environment' in twin studies is often misunderstood, encompassing more than just different experiences and potentially overestimating the impact of nurture on personality and life outcomes. Longer summary

This post discusses the concept of non-shared environment in twin studies, arguing that it's often misinterpreted. The author explains that the 50% attributed to non-shared environment in many twin studies isn't solely about different experiences, but includes measurement error, random chance, and biological factors. The post breaks down various components of non-shared environment, including measurement error, luck, biological noise, immune system differences, epigenetics, and genetic mutations. The author suggests that the actual impact of different experiences (nurture) on personality and outcomes may be smaller than commonly believed, citing a review by Eric Turkheimer. The post concludes by suggesting that this interpretation could mean nature is more important than previously thought, making social interventions more challenging and genetic engineering more tempting. Shorter summary