studied as the presence or absence of 7 repeats of a 48 base pair sequence (i.e. 7− vs. 7+). The 7+ variant is associated with decreased neuronal dopamine signaling and thus provides a potential functional link between genetics and behaviors related to threat assessment. In addition, DRD4 is expressed at relatively high levels in the prefrontal cortex (Oak, Oldenhof, & Van Tol, 2000), a region of the brain related to cognitive control. Given the implications for dopamine-related neurological processes, DRD4 has been the subject of study in many areas, including a large literature on novelty seeking and attention-deficit/hyperactivity disorder (e.g., Faraone, Doyle, Mick, Biederman, 2001; Kluger, Siegfried, & Ebstein, 2002).
