The only legitimate exception to this limitation requires perfect or nearly perfect additivity between genotypic and environmental effects, such that differences among genotypes are the same in all environments and differences between environments are the same for all genotypes

But notice the waffle words used by Watson and on the cover of Life: “in large measure” and “mostly in your genes.” Everyone is an interactionist these days, in some sense of “interaction.” Genes and environment, or nature and nurture, are recognized both to be necessary for development: by themselves, genes can’t determine or do anything. Yet, theorists still seem to give the nod to one or the other, suggesting that it is mostly genes or mostly the environment, mostly nature or mostly nurture,