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