(Kondacs & Szabo, 1999). Stability estimates for delta power are typically smaller (Gasser et al., 1985; Kondacs & Szabo, 1999; Pollock, Schneider, & Lyness, 1991). In addition, individual differences in developmental trajectories have been reported that distinguish children with autism from normally developing children, and it has been proposed that growth curve parameters might constitute promising endophenotypes for autism spectrum disorders (Tierney, Gabard-Durnam, Vogel-Farley, Tager-Flusberg, & Nelson, 2012). Individual differences in EEG activity are highly heritable (Enoch et al., 2008; D. J. Smit, Posthuma, Boomsma, & Geus, 2005; Tang et al., 2007; van Beijsterveldt, Molenaar, de Geus, & Boomsma, 1996), with published estimates of heritability on the order of .80. Heritable individual differences are particularly evident for alpha power and alpha peak frequency, becoming somewhat less prominent toward either end of the power spectrum from the alpha band.
