DRD4 and attention deficit-hyperactivity disorder: The 7-repeat allele of the DRD4 polymorphism has been associated with several behaviors and experiences, such as cigarette smoking [41]–[43], cue-elicited craving [44]–[47] but see [48], pathological gambling [49], [50], laboratory measures of financial risk taking and inhibitory motor control (e.g., [51]–[54]), fairness preference [55], human assortative mating patterns [56], and infidelity/sexual promiscuity [57], as well as disorders, such as Attention Deficit/Hyperactivity Disorder (ADHD) [58]–[60].