(312 male MZs; 313 female DZs; 166 male DZs; 182 female DZs) had P300 amplitude data available for inclusion in this study. This sample was comprised of members of 321 male twin pairs (216 MZ pairs) and 345 female twin pairs (210 MZs). 466 (70%) twin pairs had P300 amplitude and AAU data for both twins, while 200 twin pairs had at least one member missing P300 amplitude, AAU data, or both.
