carriers who also had at least one long version of DRD4 VNTR exhibited disproportionately high levels of impulsive discounting compared to the other genotype combinations. In a separate study of a locus related to the dopamine D2 gene, nonclinical young adults who were C allele carriers of the DRD2 C957T (rs6277) SNP exhibited more rapid responding during discounting, although not more impulsive discounting (White, Lawford, Morris, & Young, 2009).
