information about the participants. Quality control procedures included a genotype call rate of GE 98%, subject filtering call rates of GE 95%, non-significant departures of Hardy-Weinberg equilibrium, and outlier screening (using a criterion of 5 SDs). None of the alleles deviated from Hardy-Weinberg equilibrium (p = .87, ns). Applying these quality control procedures resulted in nine participants (2.6%) being excluded from further analyses. Consistent with previous research (Hutchison et al., 2003; van der Zwaluw et al., 2012), DRD4 polymorphism was dichotomized as low risk (two short alleles, 2-6 repeats) or high risk (one or two long alleles, 7-11 repeats; see Table 1 for frequencies of alleles and genotypes).
