Fig. 1.
Longitudinal behavioral genetic Cholesky decomposition for one member of a sibling pair. The latent variables A, C, and E represent the influence of genetic variation, shared environmental variation, and nonshared environmental variation, respectively. A1, C1, and E1 represent these influences on cognition at the first measurement occasion (Time 1), and squaring the parameters a1, c1, and e1 gives the proportion of variance in cognitive ability at Time 1 accounted for by the A1, C1, and E1 components, respectively. The parameters labeled ab, cb, and eb represent the carryover of genetic and environmental effects from Time 1 to the second measurement occasion (Time 2). The latent variables Au, Cu, and Eu represent the unique variance at Time 2, and the squared au, cu, and eu parameters represent the proportion of variance attributable to novel influences.