| > genetic factors (that is distinct from heritability, which is lower, ~60% You’re confusing something. Genetic factors = heritability, by definition[^1]. The 60% number is simply the heritability at birth (actually it’s probably lower), whereas the 80% number is the heritability in adults. I see how this may sound confusing (how can heritability change?!). The reason is simply that “heritability of X” is, strictly speaking, a shortcut for “heritability in the variability of X”. As children grow up, they are influenced by their environment, which accounts for part of their intellectual development. As adults, they are still influenced by their environment but since the majority of their intellectual development has already taken place, there’s less room for variation here. In other words, between two toddlers there’s a lot room for variation in upbringing with influence on their IQ. But if you take two University graduates from the same school, with doctoral degrees in particle physics, they will have relatively little variability in their IQ that’s due to their upbringing. Instead, the difference in their respective IQs will be mostly due to genetics (80% of it). > but [the effect of intervention] fades into adulthood and eventual life outcomes No, that’s another misinterpretation. The effect does not fade, it’s sustained. It simply seems to fade since you are comparing a different population/peer group (see my example of the two PhDs above). --- [^1] I’m aware that there are other vague definitions of heritability and genetic factors flying around, just to confuse things. However, these aren’t rigorously defined. In genetics, heritability = genetic factors. |