Behavior genetics squares the effect sizes, which biases it very strongly against smallish effect sizes (where “smallish” includes effect sizes on the order of magnitude 0.3, which would often be considered “large” for social science because it is rare to get effects that large). It is possible for the variance due to shared environment to be small, even though the effect of shared environment is large. See this twitter thread for more detail:
Behavior genetics squares the effect sizes, which biases it very strongly against smallish effect sizes (where “smallish” includes effect sizes on the order of magnitude 0.3, which would often be considered “large” for social science because it is rare to get effects that large). It is possible for the variance due to shared environment to be small, even though the effect of shared environment is large. See this twitter thread for more detail:
https://www.twitter.com/tailcalled/status/1522876250381066242