Does the heritability of cognitive abilities vary as a function of parental education? Evidence from a German twin sample
Fig 1
Continuous moderator model for a single twin (see [47]).
The measured moderator (M) has a mediating or main effect (βM) on the trait (T), as well as a potential moderating effect on the variance components of the residual (after the main effect has been partialled out). A, C, and E represent additive genetic, shared environmental, and nonshared environmental influences on the trait; a, c, e, are the unmoderated elements of genetic, shared, and nonshared path coefficients; Mi is the measured moderator level for the ith twin pair (both twins in a pair have the same value for obligatorily-shared moderators like SES); μ = the mean of the trait (T); 1 = the constant by which μ is multiplied, values of the trait are given by 1μ+ βM.