Cognitive biases in attention have been clearly demonstrated in substance use disorders, such as the slowed naming of drug-relevant words on an emotional Stroop task, and comparable biases for gambling-relevant words are also observed in problem gamblers (Boyer and Dickerson, 2003; McCusker and Gettings, 1997). However, it is currently unclear whether distortions of probability and reasoning also generalize from pathological gambling to drug addiction. Recent data indicate that these distortions recruit neural circuitry of core relevance to the mechanisms of impulsivity and the clinical phenotype of addiction. For example, Clark and colleagues have used fMRI to study the brain response to gambling near-misses; nonwin outcomes that are somehow proximal to actual wins. Gamblers frequently recognize near-miss outcomes and report that they encourage further play, despite the objective fact that in a game of chance (e.g. the lottery), a near-miss provides absolutely no useful information to guide ongoing play. Clark and colleagues (2009) devised a computerized slot-machine task that allowed the comparison of monetary wins, near-misses (where the reel stopped one position from the payline), and “full-misses.” Subjective ratings showed that
