Fig. 1.
Bivariate correlated factors model for Armed Forces Qualification Test (AFQT) scores at baseline (age 20) and during the Vietnam Era Twin Study of Aging (age 55). A = additive genetic factors; C = shared family environment; E = nonshared environment; rG = genetic correlation; rC = shared environment correlation; rE = nonshared environment correlation. Values adjacent to lines are path coefficients; values in parentheses are the 95% confidence intervals; values in brackets are standardized variance components (h2 = genetic influences; c2 = shared environment; e2 = nonshared environment).