Impulsivity is a predisposition towards rapid, unplanned reactions to internal or external stimuli with diminished regard to the negative consequences of such reactions (Chamberlain & Sahakian 2007), whereas compulsivity represents a tendency to perform unpleasantly repetitive acts in a habitual or stereotyped manner to prevent perceived negative consequences, leading to functional impairment (Hollander & Cohen 1996). These two constructs may be viewed as diametrically opposed, or alternatively, as similar, in that each implies a dysfunction of impulse control (Stein & Hollander 1995).