Family correlations from RFGLS, which have been adjusted for effects on mean levels of the various model covariates, are presented in Table 1. The median correlation was .80 for MZ twin pairs, .39 for DZ pairs, and .27 for parents and offspring. The mother-father correlation was essentially 0. Overall, the pattern of correlations is consistent with substantial additive genetic influence and negligible shared environmental influence (Iacono et al., 2014). Table 2 presents estimates of the proportion of genetic and environmental variance in each EEG measure from ACE models, along with confidence intervals. These are estimated from data from all four family members as well as from MZ and DZ twins only. Heritability estimates were uniformly large, ranging from .49, for delta power, to .85, for beta power, with a median of .78. Estimates were very similar for family-based models and those based only on twins, especially for the higher frequencies and total power. The remaining variance was due to unique environmental influence; point estimates of common environmental influence were 0 with two exceptions: alpha power for both the occipital measure
