General Intelligence (g) and Heritability (H 2, h 2)

The Limits of Biological Influence

“…Several other statistical and methodological problems associated with the determination of heritability are important to note (Hirsch, 1970(Hirsch, , 1976(Hirsch, , 1990a(Hirsch, , 1990bHirsch, McGuire, & Vetta, 1980;Lerner, 1986;McGuire & Hirsch, 1977;Wahlsten, 1990). A key problem arises in regard to differences between the concept of broad heritability (H2) and the concept of narrow heritability (h2).…”

“…If heredity and the environment interact, the calculation of heritability is quite problematic (Bullock, 1990;Feldman & Lewontin, 1975;McGuire & Hirsch, 1977;Wahlsten, 1990). However, in assessing heritability among humans, the statistical techniques used to determine if there is evidence for heredity-environment interaction (ANOVA or its equivalent, multiple regression) are not as sensitive to the presence of interactions as they are to the independent (and hence additive) influences of heredity and environment.…”

“…HZ is of little interest in genetics (McGuire & Hirsch, 1977), primarily because it does not allow the contribution of genotype variance per se to be disentangled from environmental variance; and, of course, such separation is an objective of heritability analyses in the first place.…”

“…Narrow heritability (h2) is simply the proportion of variance in behavior that may be attributed solely to the main effect of hereditary (genotypic) variance; that is, h2 is the hereditary variance that exists independent of, and thus merely separately adds to, environmental variance (McGuire & Hirsch, 1977). It is the determination of h2 toward which most heritability analysis is aimed.…”

Jerry Hirsch (20 September 1922–3 May 2008): A Tribute

“…I have found implacable and scientifically based criticism. The critical approach to the use of the tools of quantitative genetics (McGuire and Hirsch 1977b), and in particular of the concept of ''heritability'' is not marred by ideology. The criticism he expressed at the time, and even later, is shared by many people in the community of geneticists.…”