drinking measures) and outcome (here, ERP measures) are moderately heritable, discordant co-twins will be limited in number, and power will be constrained. In a second within-family analysis, we used all twin pairs with usable data from both co-twins on both sets of measures and correlated intrapair differences in drinking measures with intrapair differences in ERP variables; the quasi-continuous nature of both drinking and ERP measures was expected to give this analysis necessary power for within-family confirmation of effects of drinking on ERP amplitude and latency.
