Participants received a structured interview regarding their drinking patterns, including length of abstinence and duration of heavy drinking, ie, the number of years they consumed more than 21 drinks per week (one drink: 355 mL beer, 148 mL wine, or 44 mL hard liquor). A Quantity Frequency Index,67 which roughly corresponds to number of daily drinks, was calculated for each participant. This measure factors the amount, type, and frequency of alcohol usage over the last 6 months (for the nonalcoholic groups), or over the 6 months preceding cessation of drinking (for the alcoholic groups). For one alcoholic participant with a Quantity Frequency Index value lower than three daily drinks, the last 6 months of heavy drinking was used instead. The alcoholic participants met Diagnostic and Statistical Manual Fourth Edition criteria for lifetime alcohol abuse or dependence for a period of at least 5 years, and had abstained from alcohol for at least 4 weeks prior to testing. Inclusion criteria for the currently-smoking group was based on self-reported cigarettes currently smoked per day, and duration of smoking was the number of years that the participants smoked their current amount of cigarettes.