Decades of twin studies, consistently replicated across dozens of large-scale studies, have found that family environment explains effectively 0% of the varianc

Decades of twin studies, consistently replicated across dozens of large-scale studies, have found that family environment explains effectively 0% of the variance in adult IQ. In contrast, genetic heritability explains well over 50% of the cross-sectional population variance[1]. Always keep this indisputably true fact in mind when reading association studies like the one in the link. In fact one simple exercise is to imagine a close analogy between intelligence and height. After all, the structure of adult IQ inheritance closely matches that of adult height[2]. Imagine if you read a study that found that kids whose parents frequently played basketball were several inches taller. Would you conclude that basketball causally increases height? Of course not. Given what we know about the highly genetic hereditary nature of height, there's a much more logical conclusion. Tall parents pass along their genes and tend to have tall kids. Tall people are more likely to play basketball. Therefore basketball players are more likely to have tall children. When you have highly genetically inherited traits like IQ or height, association studies can find all sorts of superficially compelling ways to supposedly improve the trait. However all of these findings are basically worthless unless we control for genetics, for example by pairing siblings. [1] https://www.sciencedirect.com/science/article/pii/S1041608007000982 https://www.sciencedirect.com/science/article/pii/S104160800... [2] https://www.scientificamerican.com/article/how-much-of-human-height/ https://www.scientificamerican.com/article/how-much-of-human...