and 1b for details). Analyses were repeated with and without thesethree twin pairs to obtain results at both classification thresholds.Supplementary Tables 1a and 1b related to this article canbe found, in the online version, at http://dx.doi.org/10.1016/j.bbr.2015.02.024.After interviews and testing, one twin pair was excluded fromthe study because neither twin scored below 1.43 on a colored-sequence battery test, classifying both twins as unaffected. Twopairs were excluded due to lost contact, and one pair was excludedbecause of indeterminate zygosity. Although zygosity was deter-mined through self-report, all pairs included in the analysis eitherreported reasonable confidence in their zygosity or provided medi-cal evidence (e.g. blood tests, physicians’ reports at birth). The finalanalysis includes 34 twin pairs (68 individuals; based on [25]) andis repeated at the more conservative classification threshold with31 twin pairs (62 individuals; based on ).