non-familial variance that is difficult to account for statistically. Both family (Anokhin, 1989) and twin (Zietsch et al., 2007) studies employing multivariate genetic analysis of absolute power measures of EEG frequency bands point to high phenotypic and genetic correlations among powers in different frequency bands, suggesting the existence of a common genetic factor influencing the overall amplitude of EEG oscillations. As mentioned above (section 3.1), bivariate genetic analysis permits a decomposition of covariance between two variables into genetic and environmental components and thus the assessment of the degree of overlap between genetic factors influencing two variables.
