Summary of best fitting model (as indicated by AIC) for three indices of SES.

§Best fitting model as indicated by Akaike's information criterion (AIC); SES index 1 = a composite of parental education and occupation acquired when the TEDS twins were 18 months old; SES index 2 = a composite of parental education and occupation acquired when the TEDS twins were 7 years old; SES index 3 = family income measured when the TEDS twins were 9 years old; a, c, e = unmoderated genetic, shared, and nonshared environmental path coefficients; βA, βC, βE = moderated genetic, shared, and nonshared environmental path coefficients; βM = main effect of moderator on mean of IQ; ◯ = includes C moderation; ⊙ = C moderation only.