1958). Using measures such as percent-time alpha and the dominant EEG frequency, Vogel has shown that MZ twin differences on these quantitative measures do not exceed average differences between the right and the left hemisphere of the same person. Because test-retest reliability serves as a theoretical upper limit for MZ correlations and heritability, these early studies suggested that the stable, trait-like variance in the human EEG is almost entirely determined by genetic factors.
