Figure 1: Biometric cross-lagged reduced model for Callous-Unemotional Behavior and negative parenting, shown for one twin.

Dashed paths indicate nonsignificant paths that could be dropped from the model. The model constrains all cross-age associations to function as phenotypic partial regression coefficients. The paths leading from CU at age 2 to CU at age 3 index stability, controlling for any prior association with parenting. The cross-lagged paths reflect the effects of CU at age 2 on parenting at age 3 and visa versa, above and beyond their preexisting relation at age 2 and stability effects. The variances of CU and parenting at age 2 are decomposed into their genetic (A), shared environmental (C), and nonshared environmental (E) components. The genetic and environmental effects at age 3 are residual effects that are independent of age 2, and reflect change. Paths between the latent A, C, and E factors and each phenotype are standardized partial regression coefficients, and indicate the relative contributions of A, C, and E factors to each phenotype. The square of these paths represents the genetic and environmental variance associated with each phenotype. Confidence intervals are presented in parentheses. r_g, r_c, and r_e denote the genetic and environmental correlations. A=Genetic influences; C=Shared environmental influences; E=Nonshared environmental influences; CU=Callous-Unemotional Behaviors^aResidualized for sex and conduct problems.