Figure 1.

Simulated within-family phenotype–environment effect model. X, simulated phenotypic twin score; A^b, between-family genetic effect; E^b, between-family environmental effect; $A_i^{\mathrm{w}}$, within-family genetic effect; $E_i^{\mathrm{w}}$, within-family environmental effect; b_PE, phenotype–environmental effect of low (0.10) or moderate (0.40) value. A^b and $A_i^{\mathrm{w}}$ variances on the left-hand side of the slash (/) specify MZ twin variances and DZ variances are on the right-hand side.